It is the 20th September and my son’s turn to cook the roast. Which I feel better about as it is 16˚C out there. Yet, much like high summer, we were pulling 3kW off the roof. My son insists on using the main oven, so it takes forever and uses so much more electricity. Why won’t he use the microwave and combination fan oven?
Yet, the photovoltaic cells were up to the job. Indeed, I have an old K750 Logitech solar powered keyboard newly discovered and charging. A solar phone charger charging up my battery pack for the insulin pump. We’re still pulling 3.1kW off the roof at 2pm, as I am writing this. When you have solar panels, it does feel like the gift that keeps on giving.
Since I now work for myself and the house has a lodger, I tend to lie in bed on a Saturday after the alarm goes off. I listen to the news without the hurry to get up and going. Jim Ratcliffe was saying that the UK was going to run out of gas due to failure to buy gas and store it for our winter.
As we have the battery and the solar cells, I am not sure I am that worried. It would mean living very differently. We are not dependent on gas for heating, and during the day, we can get some power off the roof. Indeed, we can’t power everything from the roof over winter, but we generate enough to cover our heating.
Just as importantly, we get solar gain from the heat of the sun too. It’s only 1-2˚C for a room, but it lowers our need to power our heating. With the insulation and triple glazing, once we get to temperature, it pretty much sustains itself.
I will share the Energy Dashboard Map to show how much renewable capability we have. Yet we are not using that power. It could be that we don’t have it ‘hooked up’ yet. But what does commissioned and operational mean if that is really the case?
The image here shows a great example: Port of Tilbury Green Hydrogen plant was commissioned on the 1st May 2026, and is now operational. But it disappears when the ‘Live’ view is shown on today’s dashboard. Why? At 1 MW it is a small contributor, but teamed with the ‘Live’ Tilbury Biomass generator, it would contribute 44MW, which is 0.1% of the current requirements in the UK. It doesn’t sound like much, but of the 23.4 GW currently being generated, we are only producing 76 gCO2eq/KWh and I think we have the capability of doing better.
Looking at this snap-shot, we are exporting a huge amount of power out to Europe. Exactly what we should be doing. Yet we have a gas turbine running at 410 MW at Rye House. Enfield Power Station is contributing 250 MW, while 100s of solar farms in the surrounding area are producing nothing. Why?
I am not saying those plants are running at full pelt right now. It is a dull October day. Those plants are producing something that can help. Even we’re covering our base needs with solar power right of this moment. We’re even stowing the remainder of the power in our batteries, just as the UK can do. Across the UK we have some huge batteries able to pull in excess for times when there is less renewable power available. We have 93% of our batteries available with 122 MW being produced from them.
The seven live solar farms are producing 203 MW. That’s seven sites out of 1,399 = 40,500 MW. Enough for our needs and to supply our town, just with solar power. Wind power has 151 out of 832 sites live producing 16,088 MW. If all the wind farms were generating, that would be staggering.
I am not worried about running out of gas. I do ask this, so no-one has to be worried about it. Why we don’t have more of our renewable and operational renewables sources on line?
If this is about the heat pump again, I am going to scream!
Look at category, not about the heat pump. Directly.
OK, I’ll bite, what is it about?
EPC’s, baby. We did it, we got our A certificate. A very reasonable certificate A score.
Congratulations.
A little enthusiasm, please. But I am a happy bunny.
Just a grade, doesn’t mean anything.
Actually, the Energy Performance Certificate is much more than just a grade. It is the definition of how sustainable our house is to live in. People talk about curb appeal, but when natural gas prices are high, our lives are relatively predictably constant in terms of what it costs to run our house. It was one of the things we looked out for when we were hunting for this house.
For three months this year, 95% of the energy we used came from our roof. Our electricity usage bill for June was £3.81. For the whole year, we have supplied 46% of the energy we have used.
I know some have done better, but few of those houses were built in 2012 in a town and have a floor area of 244m2 and only a 4kW solar array. They were not built running off a gas boiler. They did not have an electricity bill of £110 in May 2013.
From the outside, apart from the Tesla Powerwall batteries, solar array, and the heat pump’s propeller fans are the only clues to what might be going on inside. It’s a pretty standard, albeit bit large, red brick house. As seen in the photo at the top of the page. Doesn’t look like anything special, sustainability-wise. It does not have cedar cladding or fewer windows. It is just an normal looking home.
That’s what the EPC is meant to do, show you what is under the skin and give you an idea of what it costs to run the house with the technologies you have.
OK, I didn’t think it mattered that much. Higher grade (A) is better than a lower grade (D) but it’s just theoretical.
Not at all. Take the current situation with oil and gas prices. If you have a house like ours and it was a grade E, it would cost you a small fortune to keep it warm and lit over the winter.
Everywhere in the UK has winter. We are a small, damp island floating in the North Atlantic, 38˚ south of the polar region. We are closer to the poles in East Anglia, than we are to the equator, which is 52˚ south of us. I love that, I love the fact we get seasons and can grow most things, but the winters are cold. Possibly colder now thanks to global warming.
Ironically, the pressure of fuel costs has driven up the uptake of heat pumps for many who have relied on oil fired boilers in the past. Fuel theft has been a real issue in our region.
We were on mains gas, but it was always our end goal to move to a heat pump.
But before we got our heat pump, we had already obtained an EPC certificate B. In fact, one of the things that made the heat pump possible was reducing our need to burn copious amounts of fuel to keep warm.
Isn’t that a chicken and egg scenario, if you lower your fuel costs, you don’t need a heat pump?
There is so much to unpick there! Let’s start with the premise that you are looking at lowering your fuel needs. It is always good to run an efficient home. Basically it works out like this:
heat the air of the home -> heat the fabric of the home -> lose heat through convection and conducting heat through walls and windows -> replace heat -> back to heating air in the house.
But I am teaching my grandma to suck eggs here, we all did that in middle or high school. Your picture may have a different heating mechanism, but this is what ours looks like. Within the house you may have auxiliary heating such as plug-in units or a fire.
All houses have some loss, the trick is to reduce that as much as possible. Some approaches use PassivHaus methods, being basically airtight with a heat recovery system circulating fresh air. Others need to breathe to get fresh air into them, so cannot be completely air tight. Ours is one of those houses. We have vents in the brickwork and the windows, allowing air circulation to happen, but we lose some heat.
Good to great insulation helps a great deal to reduce those losses. But simple things make a big difference during the heating seasons.
Close the curtains at night. Windows are rarely as good as walls, but a set of thermally lined curtains, or a thermally insulated blind can make a huge difference at night. In fact, layer up your window dressings: a thermally insulating roman, roller, or Austrian blinds provide extra insulation during the colder months. If you really love a pair of curtains and can’t justify replacing them, Dunelm sell thermal curtain liners you can add to unlined hung curtains for the winter.
Open the curtains during the day! Solar radiation coming in on a sunny winters day can help reduce your heating needs. It’s called solar gain and we deliberately kept a couple of the windows in our house that faced due south as double glazing for that purpose. During summer, use external blinds and awnings to reduce the solar gain!
Door curtains (aka portières) do a very similar job, often more effectively for front and back doors.
Reduce drafts under doors with bought draft excluders (tubes of fabric stuffed with fillers) or make your own out of old tights, socks, or trousers, stuffed with beans, polystyrene, waste fabric, or paper.
Shut internal doors.
Turn down the flow rate on your boiler. As a zero cost thing to do, this is so easy. Most boilers are left at a 70-75˚ flow rate. Turning down the heat allows a modern condensing boiler to work more efficiently as they condense well when the return rate is below 54˚. Setting your flow rate to 55˚ can move your boiler efficiency from 80-85% to 90-94%,
Use zoned heating where possible. If you have radiators and thermostatic radiator valves (TRV), swap out the TRVs for smart ones. These can be programmed easily through an app to provide the heat you need, where and when you need it.
You don’t have to pay for subscriptions to make them work well. Geofencing is something you can do manually, and timed schedules work amazingly well during the week, especially if no-one stays at home during the working week.
OK. Does not look like it is that easy to go from an EPC C to A, like you have done, then?
Actually, work with those pointers above and with a normal house and they will help reduce your need for excess energy for heating without huge outlay. Really achievable and doesn’t have to be done as a big bang.
We took 4 years to go from a B to A, 6 years to go from a C to B. Those first steps were all about reducing our costs and making it more comfortable. Those investments were tried, assured that they would work for us and then rolled out.
Why take such a long time? Well, when I bought our smart TRVs they cost £35-50 each. We have 8 of those, just upstairs. Of course we did that slowly to see if they provided benefit. They are now much cheaper to get.
The smart wired in room thermostats that go with them were £100-120 when we bought them. We have 5 of those. We did them over two months. At no point did I spend more than we could afford to do in a month. Why would I? Buying in spring and summer is cheaper than buying in autumn. The big purchases I did when it was cheaper.
Did it make a difference?
Year
Total energy used (kWh)
2021
19,509.120
2022
15,013.391
2023
13,270.888
2024
N/A
In 2021, we were running with Heatmiser programmable thermostats and manual TRVs, and a higher flow rate. In October 2022, I started the rollout of the smart TRVs and turned down the flow rate.
January 2023, I completed that task. 2024, we got the heat pump, so I don’t have figures for the whole of 2024, but as our gas boiler died on the 24th March 2024, I am happy to say it’s more or less proven figures. So 2022 still looks like a high consumption rate, but of course we’d ‘bought the gas’ from January to March 2022 while we were running the ‘old equipment’ and their settings.
We went from an annual usage of 19.5MWh in gas to 13.2MWh just by a set of tasks that for our house cost £860 and would be far less today, as the technology is far more widespread. Our energy supplier said our CO2e footprint for energy went from a 2.6 tonnes pa to 1.3 tonnes pa, just from reducing our consumption.
That 6,239kWh saving would cost £497.25 today: so in two years I recouped that money. In 2021, gas was £0.0202 per kWh and electricity was £0.1308 per unit. At the time, I was saving money but the pay back would have been much longer. But we had made the change before the conflict between Russia and Ukraine happened and prices quadrupled. While others were facing huge hikes in their energy bills, we were sitting comfortably back at where we had been.
Now one of the things the EPC assessment does is work out the energy you need to heat, light and provide hot water for your house. My gas consumption covers the heat and providing hot water part. But of course, LEDs are a brilliant way to light your way for very little energy. This means you can work out if you are running at top efficiency. NB: I haven’t spoken about turning down the thermostat, we did all this and kept the temperatures the same.
OK, that makes the EPC much more meaningful.
Doesn’t it?
An EPC B house with a gas boiler is much easier to run than an EPC E house with a heat pump, potentially. Not likely to have an EPC E house with a heat pump and here’s why.
A boiler has a coefficient of performance (COP) of 0.85. A heat pump typically has one of 4. That means a gas boiler gets 0.85kWh of heat produced from 1kWh of gas. A heat pump gets 4kWh of heat out for 1kWh electricity. So the COP is a multiplier against the energy for the heat you receive.
Our heat pump needs approx. 4MWh of electricity to produce the same heat compared to 13.27MWh of the gas the old boiler did.
That’s why you are unlikely to see a heat pump in a house with an EPC lower than C, if it were assessed today (not true two years ago, but the way heat pumps were viewed changed dramatically as the UK grid’s carbon intensity fell). Heat pumps are just more efficient.
It has been one of those Sundays. You know the ones I mean, you wake up with good intentions. Of taking it easy, having a proper day of rest. Instead, you paint a couple of walls in a bedroom, including all the clearing up. You cook a roast dinner and make 750ml of stock. And prep the joint for the left over meals next week.
“I feel like I’m on the gravy train” was a throw away line to my husband. He thought that was an apt summation of today.
I also want to remove all the masking tape from said bedroom (the last two walls this weekend mean the job is completed). Having had my assertions about the programmable bulbs helping us to remove “phantom loads” , I have four to fit round the house. I need to sort out trying to do the same for a couple of the other outdoor lights which has resulted in buying the wrong thing. Thank goodness for living in the UK and being able to make such mistakes. Phantom loads are where significant amounts of energy are being used without providing noticeable benefits!
And go for a long walk. I have already clocked up 4,000 steps and haven’t gone further than 100m from my bed. Inactive is not a word I would use for my time in our home. Up to a point, it’s why I have the home I have. I can do mad things like decorate a room without it bring chaos in its wake, and I can cook up a storm in the kitchen. Sorry, just having a break to fetch stock out of microwave and get the dishwasher on.
The long walk did not happen. But I did cook tea.
Don’t you run the risk of being called the Lighting Meanie again?
Home automation does not automatically meet a welcome reception. We did have some ‘false dawns’ as we started out journey!
As a family learning to make the most of home automation, we have all come a long way since then. As our son has moved back home, we have come to an arrangement about how everything works for us all.
It does take negotiation and everyone has a valid say in this. Lighting is a basic human right, after all! Google home has also helped, by grouping the lights and temperature control for a home in one place. While I use the Tapo app for much of the power sockets and lighting control thanks to ‘scene automations’, being able to turn on and off my bedside lamp from my watch is worth its weight in gold!
I am so glad I got our Kasa wifi controlled sockets and then lights back in 2014. Unlike more modern versions, they need nothing more than a wifi hub in the house. No Matter Controllers, no proprietary hardware. Plug them in, pair them to the wifi and go. Share the Tapo/Kasa with Google home or Alexa or whatever, and go. Simple, low powered. Just works.
All of the sockets are powered up all the time, the bulbs are pretty much 50:50. When the lights are left on, it is so flexible in how you switch them on. If you switch them on, the easiest thing to do is say what happens when they “power up”.
So you really are master of it all?
For me, the best thing is the automation for when we go to bed. As the TV and lounge lights turn off, the hallway and bedroom lights come on. When I am in bed, I then switch off the bedroom lights that are no longer required and all the hallway lights. Our landing light is on a switch only accessible from the far end of the house, so this makes things very civilized.
The biggest thing it has given us, of course, it the ability to manage our electricity use. Even on standby, our TV draws much more energy than the smart socket does. This has allowed our base load to drop to 100W most of the time. With the Powerwall, that allowed us the ability to run from our batteries most of the summer. The UK grid provided us with just 5% of our energy over June, July, and August. And only 27% over September.
That was our car driving (Nissan Leaf), cooking, vacuuming, dishwashing, clothes washing, tumble drying, hot water, hair drying, tooth brushing, shaving, working (computers and monitors), phone using, game playing, etc. When I stop for lunch, during the week, my monitor powers down, any lamps I am using, device charging, etc, and the only thing I use electricity for is heating my food. I could be disciplined and turn everything off, and on again, but that is not easy to remember to do every single day. And if I pop out for a walk, I can easily check on my phone whether I have powered down.
OK, so worth doing?
I wish the GU10 version of the bulbs had been available for the kitchen (although with 28 of them to do, I might have more than winced at the cost!) when I did the kitchen. The ones in our main bathroom are brilliant – one of the rooms where we do use them as a regular light bulb, but the lights come on at 50% strength normally, but you can dip them right down to 1%, or have them off completely but allow the extractor fan to run without the load of the lights.
We have 7 more lights where they could be applied.
As for my office and the lounge, it would be hard to run these as cheaply. During the winter, when I start work, the desk lamp comes on automatically. When the nights draw in, the bulb comes on again 30 minutes before sunset, allowing me to work without pause. Then when ‘Sam stops work’, everything shuts down, the lamp waits 3 minutes allowing me to tidy up before fading out.
It’s not just saving us from using excess energy, it’s improving our quality of life.
This post ties in with this episode on the podcast, which looks at what home automation can give you.
I promised results from April, so this is a little late. Here they are as a follow up to Going with the flow. We made a change to the temperature at which the electrical heater comes on for our heat pump. The question is: was that worthwhile?
Our heat pump gives us the means to capture the information seen in the table below, as seen here. The Heat generated in kWh ÷ Total energy usage in kWh gives us the Coefficient of Performance (COP). Click on the image to see all the details.
If we compare that month by month, we can see how we doing in terms of energy used. During the summer, that energy comes from our solar panels, so is interesting but essentially free. During the winter, that might not be the case, so we need the COP to be as high as possible!
In fact, even the during the summer, making the most of our solar means we can do more with it or even sell it back to the grid as SEG. We need our heat pump to help us make the most of the energy available to be as sustainable as possible.
Month
Total energy usage (kWh)
Compressor usage (kWh)
Heater usage (kWh)
Heat generated (kWh)
COP
January
1,003.5
941
62.5
3,440
3.42
February
608.9
581
27.9
2,390
3.93
March
505.5
477
28.5
2,080
4.12
April
233.7
220
13.7
1,110
4.75
May
151.5
147
4.5
744
4.91
June
45.7
41.1
4.6
174
3.81
July
37.8
37.2
0.6
185
4.89
August
38.5
30.5
8.0
183
4.75
September
43.2
43.2
0
253
5.86
October (so far)
47.9
47.9
0
274
5.72
November
December
Totals
2,716.1
2,565.8
150.3
10,833
~4
Last year, from Going with the flow, we can see the four months used 122.6kWh from the electrical heater. This hurts the performance of the heat pump as the electrical heater has a lower performance than the heat exchanger: only 1kWh of electricity generates 1kWh of heat. So, anytime that happens means our heat pump has performed worse! What was going on?
Apparently, I hadn’t switched off the electrical heater, I had just said “by preference, please use the compressor”. I only found this out once we’d had a service. Amazing what you learn from the people who really know their stuff!
I was shocked when checking the figures for August. Despite a really warm month, we had used 8kWh of energy by using the heater. How?
Deep in the settings, I found the kill switch and September, despite being cooler has been much more performant.
June is particularly poor!
Yes, it was. When you consider that January was colder than June by a whole 22°C, meaning in January you need to use more electricity in the heat exchanger, it’s a shame I hadn’t go the settings right for June.
Given that background, June’s COP being only a few points of a percent better than January means something was very wrong in the settings! If England expects every one to do their duty, I do not expect a COP below 4.5 during the height of summer!
Before the service in June (and I should have been paying attention), our COP was steadily climbing. A hot summer should mean we don’t need the heater at all. As it is likely to be a milder winter, it’s arguable whether we’ll need it this winter either.
So, I’m feel a bit disappointed I didn’t spot that setting much sooner after the service. Having had the kind of summer where we really did just turn off the heating in May, it would have been great to really enjoy the heat exchanger doing its stuff. While the heating was off, the DHW (direct hot water) is the primary focus of our heat pump. Making sure that is making the most of ambient heat during the hottest period of the year is what should be happening!
Something to use, then?
During the summer, yes, probably during the equinoxes too. But having that safety in play for the winter is important too. Along with “heat curves” which provide the programmes for the heat pump to use when the temperature drops.
During the spring, summer, and autumn, a heat curve of 0.7 provides staggered levels at which the heat flow temperatures are deployed. 0.7 says a cool temperature should be used in the heating circuit until the temperature gets to 0˚C.
By comparison a heating curve of 1.3 has that cut off happening much sooner and at a higher level. Perfect when it is consistently below -5˚C, but for a typical British winter, a curve of 1.0 is much more appropriate.
Meteorological winter begins on the 1st December. I plan to switch the heater capability back on then as it can lengthen the longevity of the heat pump’s compressor. So, that will be well worth doing!
This seems an odd time to write this post, as there is no anniversary coming up. But it is a conversation that comes up every so often. Here’s my answer to it.
When we first got our Nissan Leaf Tekna in January 2014, it inspired this section of the blog, and ultimately, the podcast of the same name, Driving off the Grid. Many of us early adopters made this choice because we wanted to lower our carbon footprint. The question is, did we manage it?
Working out of total cost of ownership, carbon dioxide wise.
Basically, through car wings, we knew our efficiency was around 5 miles per kilowatt, or 0.2 kWh per mile. We’ve done 44,682 miles since we’ve owned it. Therefore, about 8,936.4 kWh, or 9MWh.
Now, we got solar cells in August 2014, so our first 4,000 miles were driven from the UK grid. After that, around 55% were charged from the grid, the other 45% from our solar cells.
(These are all averages. During the summer, we were 100% solar powered, during the winter, 35%. Now we have the house battery, nearer 75% all year round. My best ever efficiency for a journey was ten miles per kW, my worst was 3.7 miles per kW, five per kW is what we tended to average over a month.)
So, 4,000 used 800kWh which would have generated 335 kg carbon dioxide. The grid supplied 22,375.1 miles *.2 kWh = 4,475.02 kWh, over 12 years 8 months. Our solar cells provided 18,306.9 kWh at 0g of CO2 per kWh. Let’s split the remaining 4,475.02 kWh over that time, circa 353.292 kWh pa.
Given those figures as our base line, we then look at the carbon intensity of the grid, as provided by NESO.
See the table below for how that gives our carbon footprint per annum for each year of ownership.
Year
Grid kWh Consumed
UK Grid Carbon Intensity (g/kWh)
Estimated CO2 Emissions (to 2 dp in kg)
2014
353.292
419
387.64
2015
353.292
350
123.65
2016
353.292
300
105.99
2017
353.292
250
88.32
2018
353.292
230
81.26
2019
353.292
210
74.19
2020
353.292
180
63.59
2021
353.292
170
60.06
2022
353.292
160
56.53
2023
353.292
150
52.99
2024
353.292
124
43.81
2025
353.292
126
44.51
2026 (Jan–Sep)
353.292
126
44.51
Total
4,475.02
1,322.45kg
So, our travels in our Leaf have caused around 1.3 tonnes of CO2 to be generated.
The producing the battery would have caused ~3.6 to 4.8 tonnes of CO2 to be generated. Thus our total carbon footprint has been 3.9 tonnes.
That’s an awful lot for a green vehicle.
Shall we compare? Petrol and Diesel are much easier to compute. They have fixed CO2 footprints per mile.
Petrol car would have generated around 280 grams per mile, so 12,510.96 kg. A Diesel one would have generated around 277 grams per mile, so 12,376.914 kg.
So, essentially, we have saved a maximum of 7,588.51 kg of CO2. We have used considerably less than doing those journeys with a car with an internal combustion engine (ICE).
But that is not the full picture. We swapped out a 2008 BMW 650i. It generated 430g of carbon dioxide per mile. That car would have generated 19,213.26 kg instead. By comparison, we saved 14,290.81 kg.
Now, many would argue that building a new car uses more carbon dioxide than running an old car. I have ignored what the total cost in terms of carbon dioxide for making the BMW or the Nissan. I have assumed they are equal, but I did take out and include the battery.
When we look at the engine block, pistons, exhausts, spark plugs, etc, servicing costs, they probably equate. Of course, our battery and car are still on the road and still performing as well as they did coming off the showroom floor.
Per mile, and in its life-time, the EV is using 110g carbon dioxide per mile and this is just going down, as > 90% of the energy we use for the car this year has come from our solar cells and home batteries.
At some point, our battery is going to need replacing. I think it makes sense to do that.
In terms of financial cost, a new 24kWh battery would cost us ~ £2,500 fitted and including VAT. A 40kWh battery would cost us ~ £4,800 fitted and including VAT. We’d still be better carbon dioxide generators than using the old ICE car. In general, ICE produce more CO2 as they get less efficient, pistons get clogged, pipes get blocked… I ♥ our Leaf.
If you’d rather listen than read, check out the partner episode on the Driving off the Grid podcast, published on the 2nd October 2026.
I had an apprenticeship as a young adult, that allowed me to live 250 miles from home. I had to buy a fridge for my insulin, and as an 18 year old, I did that on a credit card and paid off the total of the fridge with my first three pay checks after rent, food, extra.
By the time I was in my third year, the thing I bought as an essential treat was my first microwave. I wanted it for proper cooking for as well as the traditional reheating. I bought a fish steamer for the microwave and, when I was on my own, that was my meal of choice. A steam trout cooked in minutes in the microwave.
By the time I was living on my own at University, my Sunday lunch was typically a tin of Jersey potatoes, a whole trout, peas and any veg I had left over. A meal for kings for less than £3 and cooked in 5 minutes! That was between 1994 and 1997.
Jump to 2026, I’m a busy professional. It’s my turn to shop this week and I tend to do that before shutting myself in my office. I happen to know I’m on my own this Friday for tea. So, how to give myself something tasty, easy, and sustainable to cook?
Image my surprised when in Waitrose of all places, I saw a fresh rainbow trout on the fish counter for £13.90 per kilo. As a myWaitrose member, I get a 20% on a Friday for fish from the fish counter. Now, a small whole trout is 164g or thereabouts. Which makes it £2.27, minus 20%, is 0.8*2.27=£1.82.
Yesterday, for my tea, I cooked it with fresh broccoli left over from last week’s shop, 160g of Maris piper potatoes, boiled, and some baby corn left over from last week’s shop.
Essentially, these were vegetables at risk of being chucked out. But if I’d bought them on the day, about £1.50 of vegetables. In 2026, this meal cost me £1.82+1.50=£3.32. Not bad, nutritious with tons of trace vitamins and minerals from the vegetables too. I have it with a little horseradish sauce, making a meal I cook for myself in less than 15 minutes (as my Maris Pipers are not precooked).
Cooking it in the microwave allows that speed and locking in the flavours and goodness. It also means it costs nothing to cook.
My 164g piece whole fish cooked in 2 minutes 30 seconds on medium. That’s 600Wh*2.5/60=25Wh. That’s 0.025 kWh, less than 1p of electricity.
I cook all the vegetables in one pot, so pop the quartered potatoes into cold water and bring the boil. I leave the skins on. Programme the microwave with a delay of 11 minutes, for 2minutes 30 seconds, and a 2 minute standing time. As soon as the potatoes are boiling, start the microwave’s programme. When there is 7 minutes to go, put in the baby corn, and at the 5 minutes to go, pop in the broccoli.
Now, I set the table and get a glass of something I fancy with the meal.
My hob is an induction one. I put around 500ml of water for the potatoes, broccoli, and corn. Takes around 15 minutes in total, about 0.15 kWh, or £0.15*.27 =£0.04.
These choices meant I had a sustainable meal for one for less than £0.05 to cook and £3.32 to buy.
The induction pan could go in the dishwasher, as could the fish kettle and all the utensils. Now, I had a nearly full dishwasher (3 days worth of cups, plates, cutlery) so I happen to know the dishwasher cycle was around 200W. Washing up was £0.2*0.27=£0.05.
I could give you the cost of the electricity I used to drive to and from the supermarket, but a fancy meal at home including the washing up for less than £5 I think is amazing in 2026.
Especially as it was ready in under 17 minutes from fridge to table.
(I am not going to talk about making a fish stock in 2 minutes 30 secs in the microwave as I packed the dishwasher and got it going, which will allow me to make this next time I’m cooking on my own, Quick noodle soup. Have to say, I’m looking forward to trying that!)
(I’m also not going to mention that the fish steamer is useful for asparagus steaming in 20 seconds from table to dish).
When the hosepipe ban was brought in on the 11th July, it was a bit of a shock. Anglian Water were the old incumbent in the East of England, and despite very low rain fall, we get few hosepipe bans. The last one was between the 5th April and 14th June 2012! The current Temporary Usage Ban (aka hosepipe ban) is still in place.
No matter, we looked at what we were doing and, like everyone else, looked at how we could help ensure this vital commodity could be used to its full and precious stores could be available for as long as possible.
The average daily water usage in the UK is 140-150 litres per person per day (145 l pppd). We aimed for 100 l pppd, as this is the Government’s DEFRA (Department for environment, food and rural affairs) is aiming for by 2050 to ensure everyone in the UK has access to the water they need.
Could we achieve that in 2026?
I was a little doubtful. And in July, we got our usage down to 110 l pppd. To work that out, I took our Smart Water meter reading for July (6,976 l) and divided by 2 and then by the number of days in July, 31.
=> Water usage pppd = water usage ÷ (number of people * number of days in the month),
=> 6,976 ÷ (2*31) =112.516 l pppd.
So, let’s do that for June, July, August, September (so far).
Month
Usage (l)
Number of days
Number of people
Per Person Per Day (l)
June
5,140
23
2
111
July
6,976
31
2
112
August
6,345
31
2
102
September
7,475
30
3
83.1
Wait a moment, we had 30 days in June!
We had 7 days out of the house, a small holiday. If we did not change the number of days we were using water, it would look like such an outlier, as the usage would be 5,140÷60=86 l! The zero days were not counted. Of course, if you don’t have zero usage you have a major leak somewhere and that needs fixing asap.
The question is, what have we done to reduce our numbers?
Cooking and kitchen.
Ironically, we’re not washing up by hand. I have always doubted the argument that the dishwasher does better, but the numbers for us do hold up. You really do need to make the effort to clean up your cooking area religiously as you are not washing up after every meal. Saving a small amount of clean washing-up water in a jam jar gives you that capability without much effort.
Leaving the lid on your pans not only saves electricity or gas. Most soups can be made with a fraction of the water just by using the lid and stopping the evaporation. My Carrot and coriander soup uses 75% of the water if you put the lid on the pan! It retains the thickness, we just don’t waste the water.
Of course, with a roast dinner doesn’t need boiled vegetables with it. Pop carrots (wrapped in foil are incredible BBQ’d or roasted), courgettes, broccoli, peppers, and baby tomatoes in with the roast potatoes to make an incredible roast dinner.
Washrooms.
Not flushing unless we need to, makes a huge difference. Sharing an ensuite, it was something we were in the habit of doing in the morning and evening. But doing this throughout the day saves a huge amount.
Showers have the water turned off during soaping. One a day. I don’t rinse my body before rinsing my hair too. I am only washing my hair every 3 days. We each have a bath a week. That day, you do not have a shower. That brings our showers down to around 30 l a shower.
We do not harvest run off from our shower, but if the water crisis in the UK got worse, this is grey water that can be used to flush toilets for when it’s brown… Same can be done with bath water, of course.
I use the same start-stop pattern when hand washing and teeth brushing.
Eating and drinking.
Drinking water during the hot weather instead of tea. Weird but true, boiling water means some is lost to evaporation. Of course, during the heat waves, moving to water gave us better hydration too. Shifting our 2 l of drinking water to mostly drinking water makes it count more.
Cleaning.
We clean our hard floors with a steamer, which is used for the bathroom and shower room fittings. A litre of water cleans 52m2 of flooring, 3 sinks, 1 bath, and 1 shower. Try doing that with Cif, which needs rinsing down.
Watering house plants.
Left over water is used for the house plants. Grey water that hasn’t had detergent in it is ideal. Left over tea can give a bit of pep. Drained water from vegetables you aren’t using for stock or gravy is like using compost. Do remember to cool the water first!
OK, seems a bit involved…
These are habits we’ve built into our days. We cook the majority of our food at home, yet our water usage stays reasonably good. As we’re now three adults (four some weekends), we use more water for the household.
But sharing cooking and cleaning techniques, we have managed to reduce our usage per person per day. Actually, that’s the measure you need to know if you are making the right moves.
What are you doing? Any techniques or approaches were missing? Please share in the comments below.
My 6th podcast was all about resource management over the baking hot summers. While the heat waves were happening in the East of England, our local news channel asked residents what they’d like to see happening. More than a few people asked this question: we’re on an island, surrounded by sea, can’t we just use that?
Desalination.
The title sums it up, high salinity (saltiness) is not useful for many creatures, particularly not land mammals like the naked apes we are.
Desalination is the process for taking salt out of water, but potable (drinking) water has a bit more done to it besides. Our land harvested water is cleaned: soil particles, animal waste (including ours), and harmful chemicals are all removed down to a microscopic level.
While the sea might look lovely and blue, it’s a thriving eco-system with many of these features in it, not least sodium chloride which is harmful in great quantities.
The deep sea reality.
Harvesting sea water close to land multiplies some of these materials, including basic silt. Even further out, the number of living organisms (plant, animal, and other) is high in number. This means biological filters need to be used. Yet the flotsam is carefully looked after so as not to disturb the natural balance: a disaster for the natural world and highly damaging for land health too!
Such pipe work is complex and tough. Deep sea pipes need to withstand the harsh saliferous environment with exposed weather events and tides and currents all pressuring the system. 24/7, 365 days a year, these systems, vital for human life, need to be robust in one of the most extreme environments on the planet.
This is a non-trivial task, that needs to be maintained. For an installation and maintenance point of view, it is not a quick and easy fix.
Polishing the diamond.
Having achieved harvesting the water and coarsely filtering it, this is repeated to a finer and finer grain. We can’t filter out the salt, but much of the other detritus is done mechanically first.
The process of removing the salt is done through ‘exchangers’ like isobaric ones. Isobaric exchangers work by capturing the pressure hydraulic energy from a high-pressure brine reject stream. The water leaves the membranes, transferring it directly to the incoming seawater feed. By using a rotating ceramic rotor or piston chambers to act as a fluid interface, the high-pressure waste stream pushes against the fresh intake water. Systems like these recycle up to 98% of that pressure without needing to convert it back into electrical energy first, drastically reducing the load on the main high-pressure pumps. Often the salt is saved as a by-product and sold as seasoning.
This takes energy. For a highly efficient plant, it costs between 2.5 and 3.5 Wh per litre to do this stage. The total processing of land harvested water is 0.2 to 0.5 Wh per litre.
Ironically, this water is relatively pure, apart from some microbes. Pure H2O is not actually good to drink, or push through the UK water system. Some necessary minerals are put back, by passing the water through beds of crushed limestone. This gives the purified water calcium and magnesium carbonate to balance the pH and give it a crisp, natural taste. And protect the UK distribution systems.
We then need to kill any bugs remaining, to make it potable, as we do with land harvested water.
So tricky, but not out of reach. Surely better than rationing water with hose pipe bans?
In 2010, Thames Water opened their Thames Gateway Water Treatment Works (TGWT) in Beckton, East London. It uses brackish water, which has salt in it but at a lower level than sea water. Sea water has 35 parts salt per thousand.
As it is expensive to run and has faced operational hurdles, TGWT has largely sat idle. TGWT only comes into operation when water supplies are short and the conditions are favourable. To give it context, TGWT produces 100 to 150 million litres of water a day. That’s pulling out 1,100 tonnes of salt a day.
At 2.5 Wh a litre, TGWT uses 250,000 kWh or 250 MWh as day. A more usual site produces the same amount of water for 20 MWh. If TGWT ran every day, it would use 0.03% of the electricity generated across the UK.
If every coastal county across the UK had a desalination plant, we could have 5,500 Ml a day for a sum of 5.02 TWh per year. Or 2% of the current draw on the electrical generation in the UK.
We haven’t discussed that to keep building costs down, desalination plants need to be sited in towns, close to water systems, and energy sources. Thinking of the discussions going on about pylons bringing in cheap electricity from off-shore wind farms, 55 times, across the UK.
While the recent droughts have brought this idea back to the fore, it is not a quick and easy sticking plaster. It certainly can’t reduce the price of water or reduce the need to be careful what we use.
If you want to know more about how this technology is used throughout the world, please check out Wikipedia’s Desalination by country page. There’s an interesting technology called Seawater Greenhouses, which desalinates water purely for crops. It requires less processing as the water doesn’t need to be potable – think of your water butt collecting rainwater for your garden use…
We’ve been looking at insulation, and during the winter, one of the biggest influences on how much energy you need to heat your house is how many mammals are living in it.
A human being raises the temperature in a room by around 1°C, so having two people… It’s why we run many living spaces at a lower temperature: a dinning room run at 20°C (without a thermostat) is way too hot if you have six people round the table. It may be why both gas and electricity usage is much lower than you’d expect for Christmas Day (as seen in the analysis The power of Christmas ).
There are other benefits, as mostly you cook food together. Food takes heat to get warm – the more food there is, the more energy it needs to get hot. But in an oven, that is largely hidden from view. The microwave makes it much more obvious.
Why are you talking about this?
After two years, our son is moving back in with us. Which is going to change our power and water usage dramatically.
There are some definite benefits – less heat required for the communal areas, but that sits alongside downsides. Water usage is a clear one. It’s hard enough letting it mellow when there are two people in the house!
We’re geared up to charging things during the day, when the solar panels are generating meaningful electricity. We also keep sockets off when the chargers are not required. When I first got our ‘smart plugs’ and bulbs, a good friend of ours thought we’d burn more on running the wifi sockets than we’d save killing the power to the TV, for example. Actually, the 17 plugs and 19 bulbs (36 devices in total) use very little energy, our minimal draw is less than 100W an hour. Our TV alone would use 25W on standby, and as we only watch the TV for four hours a day, it costs in to do that.
At the beginning of my work day, a switch ensures the bedroom lights are turned off, my monitor is powered up and, during the winter, the desk lamp is on until the sun rises. My office uses around 100W of power an hour, so 100Wh of energy. I have a solar powered keyboard which I charge up while I have lunch, further saving power.
I see you use it other ways too…
I can get quite deep into my work. In the end, having the desk lamp turn off but leaving my monitor on at the “end of the day” subtly tells me to wrap things up without leaving me without the ability to save the work and shutdown the computer properly.
I then turn off the monitor and put on the desk lamp for two minutes, allowing me to close the door on my office without the need to go back and fetch my water bottle and mug.
A change of pace.
Of course, Tuesday was power on day for the heat pump’s heating circuit. Using thermostats means we only make use of it when needed, yet that single step should ensure the house doesn’t get cold. The insulation and triple glazing should keep that investment in energy as low as can be. I can’t believe it’s nearly been a year since we installed the new glazing.
The chores and cooking should be shared. Which should make things a bit easier. Of course, the company is more than welcome. There’s more money coming into the household too. Having got our water usage down to 97l per person per day, I wonder if that will stay the same?
Last week, A Coat for the House, Part 1 looked at what was going on internally in your property. This week, we’re heading outdoors.
External doors, windows, and walls.
Entrances and exits.
Entering with the front door, we can then go to the other entrances/exits, the windows and end up with the walls.
Poor quality front doors can leach heat. As a result, all types of door quote their U-Values, If you are in the market, it is worth shopping around for a product that works for you. A front door typically has a thermal rentiton of 1.0 – 1.4 W/m2K, though a top of the range one can get as low as 0.7-0.8 W/m2K and typically has Passivhaus certification.
Door curtain can be used to boost the rating of a typical door: keeping the curtain colour the same as your hallway palette can give a high end feel, as well as keeping the heat in.
Of course, any external door can be treated the same way to similar effects.
Windows
Windows are the next factor. If you have single glazing, the U-Value is around 5 W/m2K.
Any double glazing fitted between 1970 and 1990 typically has a U-Value of 3.0-3.5 W/m2K, and ones from 1990 to 2000 has a rating of 2.7-3.0 W/m2K. Today those values have improved to 1.2-1.4 W/m2K. So it is worth looking at whether your units could be replaced.
UPC glazing does fail over time typically within 20 years. Any window fitted in 2000 will need to be replacing before 2030, so if you can, make a budget to make that happen. Anything older has probably already failed.
Different technologies have helped make that difference, including films to reflect light and heat back into rooms for example. Triple glazing is not a huge jump, coming in at 0.6-0.9 W/m2K or a Passivhaus certified one achieving 0.5 W/m2K.
Walls, the final frontier.
Whatever your style or age of house, solid walls make up the majority of the fabric of your house. It is the hardest to treat once the building has been constructed.
Cavity walls.
In the 1920s, the UK started to introduce cavity walls. This was a modern technique whose aim was to keep our moisture from British domiciles, a protective layer against our wet weather. It wasn’t until the 1970s that insulation was added to such walls and by 1990, cavity wall insulation became a compulsory part of the building standards, first with polystyrene (often balls), then with rock wall, celotex, and finally foam.
How do I know if I have cavities and why bother insulating? More heat goes out to the roof!
If your house was built post 1930s, it is worth checking if it has cavity wall and if that space is insulated. If it has and doesn’t, get it done as soon as you can: that insulation can reduce your heat loss by 80%. The U-value for an uninsulated cavity wall 1.5-1.6 W/m2K. A wall with a U-Value of 1.5 W/m2K wall loses 30 W of thermal power per metre. Over a day, that is 24 * 30 Wh, or 720 Wh. If the wall is 6m2, that is 4.32 kWh – if you have a gas boiler, that would need to burn 5.4 kWh in gas to replace that heat and keep your room at a constant temperature. Using that number against the size of your house can help you work out your payback.
Size of external walls in metres x 24 x 30 W = thermal loss Wh x 1.25 / 1000 = amount of gas to buy to keep a constant temperature kWh.
This is why wall insulation is so critical. You don’t need an air pump to get a good EPC certificate or reduce your carbon footprint or save you money. Effective wall insulation can do all that for you. Grants exist if you are a low earner or get other benefits. There are schemes for older home owners and tenants too.
Likely costs are subject to your location in the UK, accessibility and the size of your property. Convert your wall area into kWh of gas and multiply by the cost of the gas to get the ‘payback’.
House type
Minimum cost
Maximum cost
Minimum cost
Maximum cost
Mid-terrace
£600
£1,200
End-terrace/bungalow
£700
£1,500
Semi-detached
£1,000
£2,500
Detached multi-storey
£1,500
£3,000
I get it, but my house, like great teeth, has no cavities!
Cavity wall insulation is not an option for you. What ever you do, it is likely to cost more and will need an experienced firm to help you do achieve insulated walls.
Often it involves internal or external application of foam or rock wool, with moisture protection and air blocks applied. If you are in a terrace or semi, see if your neighbours would like to team up, especially for external walls.
You may need planning permission. But this is worth doing and newer materials mean that applying internal insulation does not need to take as much space to get great results.
Or consider approaches used elsewhere in the world. Carpets were used in the Middle East to keep warmth in and provide decoration. Can allow wall materials to breathe and keep moisture free, and prevents condensation.
Bringing it all together.
Our coat for the house has many layers, but hopefully there is something here that helps you.
Remember, every bit of gas or electricity you don’t need to keep warm, reduces your bills and your carbon footprint.
This is the last part of investigating the options for insulating your home before the UK winter closes in. I hope you’ve enjoyed it.
