Finding the chase and cutting to it

Strolling through our local town centre or talking with family, it’s tempting to think that the grey skies overhead this UK winter are a sign that climate warming isn’t really happening.

Actually, they are almost certainly a symptom of climate warming in action. Compared to the past few Novembers, November 2025 was dramatically warmer and wetter. In our little bit of the world, temperatures were in the low to mid teens Celsius (55-62°F) for the first half of the month. Even when they dropped, between the 19th and 21st November, they rarely dropped much below freezing for long. Typically, in November, the nights stayed around 5.8°C.

Rainfall was significantly heavier in November 2025, nearly 1.5 times as much as expected. That might sound like good news as we’ve had very dry summers, but as we enter the second week of February 2026, the rain hasn’t stopped in some parts of the UK for 35 days.

November was a bit sunnier (despite the wet weather) too.

December 2025 was cooler towards the end but had a warm day on the 9th December of 12.5°C, a whole 7°C warmer than usual. It was drier but when the cold weather came in, another Artic blast like November, starting over the Christmas period. No, that didn’t bring snow.

January 2026, was cold. 0.5°C less than the average temperatures. In Marham, Norfolk, temperatures dropped to -12.5°C on the 5th January!

Our part of East Anglia is typically much milder by comparison. One of the benefits to living in the urban sprawl, is the council grits the roads and the sheer number of people keep things that little bit warmer. The towns in the area are typically 1-2°C warmer than the villages as a result.

Bad in the summer, but a blessing in the winter.

2025 was the warmest year on record for the UK, although we lacked the baking days of the summer 2022; 2022 had lower average temperatures though the high extremes were just that.

It’s the averages that matter. The UK benefits from being an island archipelago featuring a large number of inhabited islands: Northern Ireland and England, Wales, and Scotland being the significantly populous ones. It sits within 11 degrees of latitude and 15.5 degrees of longitude, which means what is happening at the south-westerly point is very different to what’s happening in the north-easterly point, weather and climate wise.

In my area, we benefit from a couple of things: longer days in the summer and winter, making solar panels worthwhile for home generation. We have a coastline, making off-shore wind power accessible at scale. It’s sparsely populated, having been agricultural for a long time, though the plans to build many more homes will change that.

East Anglia is also deemed semi-arid, by UK standards. We get little rainfall. The rain in mainland UK comes from the west. Which suggested the weather late 2025 and 2026 has been dominated by Atlantic weather systems. As lay people call it, specifically, the Gulf Stream.

The Gulf Stream is a current traveling from Mexico, past the USA east coast before bending towards Europe. Mexico is on the Tropic of Cancer, and unlike the Equator, these latitudes are seasonal and typically warmer than the latitudes to the north and south of these boundaries. They have seasons as a result, much like the UK, though milder winters at sea level than a relatively northern island group like the UK.

The UK should be a cold little set of islands in the winter, but the Gulf Stream contributes to the Atlantic Meridional Overturning Circulation (AMOC) which changes that by bringing milder weather up to us from the Tropic of Cancer. AMOC does this by acting as a conveyor belt: warm salty water flows towards the Artic where it cools and sinks. Colder deep water then flows southwards, completing the circulation. Freshwater from melting ice can reduce salinity and slow this sinking process, weakening the system..

One of the concerns with climate change is that the AMOC depends on differences in water density, driven by both temperature and salinity, to keep it circulating. As the climate warms, increased freshwater from melting ice can reduce salinity in the North Atlantic and weaken this circulation, potentially reducing the amount of heat transported towards the UK.

This is likely because as temperatures rise, more ice melts in the Arctic and around Greenland. This happens naturally each year, but climate change increases the overall amount of freshwater entering the North Atlantic. Ice is made of fresh water, so this added input reduces the salinity of the surrounding sea. Lower salinity makes the water less dense, which means it does not sink as readily in the far North. Because this sinking helps drive the Atlantic Meridional Overturning Circulation, reducing it can weaken the system and reduce the amount of heat transported towards the UK.

It’s February, so how can this be the topic of a post today?

Or Solar elevation and what it means for me…

Human beings have been interested in how high the sun gets in the sky since ancient Greece was a dominant power. In fact, the Greek astronomers founded an equation anyone can use to work out the elevation of the sun at any point in the earth – this was the foundation of sailors being able to navigate the world long before GPS was a twinkle in anyone’s eye.

To our modern, land-locked people, it helps us work out when sunrise and sunset occur and, in terms of generating solar power, when the peak can be expected.

The equation is h_max=90°-L+δ, where h_max is the height the sun reaches, L is the latitude of your position on the earth, δ is the declination from the sun to the earth which varies from +23.44° during summer solstice to -23.44° during the winter solstice (in the UK). Declination is the angle between the sun and the equator at the point of time being discussed. In this case, we’re looking at the maximum angle in a day.

My latitude is about +52°, so during the summer, our h_max is 90°-52°+23.44° ≈ 61.44° (read this as approximately equal to). During the winter, 90-52-23.44 ≈ 14.56°. We can see how this changes in the table and graph below.

This results in a solar elevation in Ipswich of….

So, for our little corner of the world, we can see that indeed the sun’s height wobbles between 61.44° to 14.56°. Which is fine and dandy.

A valentine’s gift…

As seen in the graph, during the year, it varies between that maximum and minimum of 61.44° and 14.56°. Today is the 14^th February, so it’s about 25.1°. Compared to any day in December, when the elevation was ~16°, it makes a big difference to solar generation potential, and why January and February are so much better for our generation than November and December.

The next consideration is your roof’s pitch (if siting the solar cells on your roof). Given our northern latitude, a pitch of around 53°, as we have, maximises the solar harvesting during the winter, but it is not ideal for during the summer, when a pitch of 35° would be more effective. With a heat pump supplying our heat and hot water, this is ideal for us.

The proof of this is seen in our solar generation figures; we typically generate more in March and April than we do in July. But we don’t need as much energy then, so it suits us.

This matters in terms of solar generation, as solar cells work best when the sun hits them as close to perpendicular as possible. Basically, if the angle is shallower than 60° or steeper than 90°, there is some reflection happening. Indeed, so much is reflected that the generation suffers. During the winter, our roof is ideal, as the angle is well above that 60° floor, but during the summer, the angle is well above 90°. The angle between the sun and your roof matters. If you want to be solar powered over the winter, your cells need to be at a steep angle. That doesn’t mean it’s ever going to be great, short days and all that, but it maximises what you have to play with.

For some, this is an argument they use to say that solar power is not worthwhile somewhere like the UK. I have never found that a convincing reason to not harness an abundant source of power used by plants in the UK for millenia. Of course, plants are a bit cannier than the average human in making the most of what is available…

For me, these changes mean a fixed installation is fine but it would be relatively simple to engineer a system that could maximise the gathering of photons pretty easily – only that is not encouraged in the UK. We go for fixed systems, often targetted at the winter gathering options. Indeed, if you are mirroring the pitch of the cells to the sun’s zenith, why not have simple systems to track the sun across the sky during the solar day? After all, this is what the common or garden plant does to ensure it thrives.

Again, not encouraged in the UK, at all. Our house was built with a due south (180°) azimuth view roof, which is a good compromise. I do not see houses being rejected in planning where that is not the case.

Our roof is limited because we are a “chalet style bungalow” – dormer windows mean we have shadows cast on our solar panels by our need for natural light as humans. Again, why not let the architects build a flat roof in 2012, maximising the potential to generate power?

Our solar generation has varied over the past 11 years between 3.3MWh a year and 3.8MWh with 3.6MWh being the modal generation (most frequently occurring). We don’t really have an easy option to put in more cells because of the roof architecture. We do have an east face we could exploit, and a west roof, but the generation potential of these surfaces is reduced.

Please planners, look at the limitations you are putting on people when plans are submitted, in these terms. What would our potential be if we’d had a standard roof?

Over the past few weeks, it feels like I have spent more time talking to Gemini than to any single person in real life. AI is helping more people in the workplace but what about easing things round the home?

I wondered if Gemini can help me lower my carbon footprint?

Of course, not being human, Gemini needs a question to get started. Mine was “can you help me convert this recipe so I can cook it in the microwave?”

I’ll bite, what recipe is that?

Soup. I know I have a induction hob but putting on a big ring for soup cooking over 40 minutes seems a bit wasteful, somehow.

There are several things I use a microwave for: roux sauces are done in second rather than minutes, fish is incrediable, chocolate fudge sauce is a guaranteed outcome. I know how much time is saved and great food I have enjoyed in cookware that goes straight into the dishwasher. What’s not to love, from that point of view?

Of course, for the “Driving off the grid” section of this blog, microwave ovens are incredible. There is no waste heat, it outperforms induction hobs for the sorts of food you would normally cook there.

My real winners at the moment are my home made yogurt, and the chicken stock.

So after zapping my fish dish this lunch time, I got tapping, exploring what I could do next with making the most of my microwave.

There are three winners, I think. A vegetable stock for my soups, some fish stock made from some fish I’ve cooked (definitely one for the freezer, my partner does not like fish!), and some conversions for my favourite soups.

A vegetable stock to be less wasteful.

Before I got in to cooking from scratch to such an extent, stock seemed like a waste of energy, when you could buy a cube or pod full of tasty stock. Hours bubbling away on the hob, boiling out bones did not sound like my idea of fun, not to mention the washing up.

Finding my chicken stock recipe was a wow moment. But finding a sensible looking vegetable stock seemed rarer than a unicorn, hen’s teeth, and flying pigs. Such things did not seem possible.

In comes a session with Gemini talking about home cooking, so I ask: “I’d love to make my own vegetable stock. Could you suggest how I could do that in the microwave?”

An initial suggestion was refined, working out alternatives to things I knew we were cooking the next day – I wanted to do a vegetable stock for our traditional Sunday evening soup. Well, the stock wasn’t bad, taste wise. 250ml of tasty stock out of things I would normally bin!

For the soup, I put far too much water in with it. When I cook the soup in a pan, covering with water is absolutely necessary. So I did the same with the microwave version – tasty but incrediably wet! Next time, I’ll just add the 275ml of stock.

But the speed, the hands off nature, the lack of piles of hard washing up. I may be a convert!

What about the verdict, beyond the taste, isn’t tradtional soup on a hob better than using the microwave?

It’s really marginal, energy-wise, not least because the microwave is running at 660W for the whole 15 minutes, where as once the soup is simmering, the induction hob is using very little power.

We’re losing some energy with the induction hob to the pan and its lid (85% efficient compared to the 90% of a microwave), but it’s really, really close.

Where the microwave does probably win hands down is the cleaning up process. Using the microwave, I used five pieces of equipment – a knife, litre jug, a silcon lid, a small measuring jug, and a stick blender to cook and serve. All but the small measuring jug goes straight into the dishwasher.

The traditional method uses a knife, a wooden spoon, a pan and lid, a blender goblet, and a ladle to spoon the mixture from the pan into the blender. Six pieces and that’s before we start to break apart the blender goblet and its lid – another five items.

Many of these cannot go in the dishwasher, hello wooden spoon and engine part of the blender goblet, but the pan and blender goblet are huge. Both take space that means the dishwasher would have fewer items for a full run, so often wash them by hand.

Gemini suggested that the induction hob might edge ahead, but I pointed out that for the total cost of ownership, the prize goes to the dishwasher, and that’s forgetting the time I’d be standing on my feet stirring the pot as the dry vegetables get cooked in the butter before the stock is added.

• Microwave = 15 minutes * 660W = 165Wh = 0.165 kWh.
• Stick blender = 3 mintues * 1.2 kW = 60Wh = 0.06 kWh.
• Dishwasher = 50 things in the dishwasher, of which this meal uses 4 of them, which runs at 0.54 kWh, so 0.0432 kWh.

Total power used to cook the soup in the microwave = 0.2574 kWh.

At £0.2656 per unit = £0.07, as a total charge, plus the standing charge.

A cheap evening meal on a Sunday evening, partly made with left over peelings from lunch. Next time, which much less water in it, check out the revised recipe at Microwave Stilton and Celery Soup!

Compared to the induction hob?

Ah, so there are more steps making up our 40 or so minutes of cooking time, but the induction hob probably used around 0.5767 kWh. If we keep the stick blender and everything else the same (though there is significantly more manual washing):

• Induction hob = 40 minutes * various power levels = 0.5767 kWh.
• Stick blender = 3 mintues * 1.2 kW = 60Wh = 0.06 kWh.
• Dishwasher = 50 things in the dishwasher, of which this meal uses 4 of them, which runs at 0.54 kWh, so 0.0432 kWh.

Total power used to cook the soup on the induction hob = 0.6799 kWh.

At £0.2656 per unit = £0.18 total cost, plus the standing charge.

Wait, isn’t that more than 2.5 times the cost, plus the washing up, and the time!

Yes, yes it is. Working out how to do things in the microwave (if possible) really does pay off.

This is another piece on how air sourced heat pumps (ASHP) work…

Oh no, can’t we talk about anything else?

Not yet, and bear with me. This is a fundamental thing to consider when trying to get the most out of your pump. But it helps to understand how a heat pump works to get understand why this makes such a big difference.

Fundamentally, a heat pump, like an air conditioning unit or fridge, uses a compressor to pull heat out of the air they draw in through the fan. ASHP use the principle of heat dynamics and some chemicals that have a low boiling point, that allows it to transfer as much heat out of the air as is possible, into the compressor. This squeezes the gas, generating high levels of heat which is conducted to the heating coils, which heat the water going to the radiators or the hot water tank.

This is why ASHP are so efficient compared to a fan heater or immersion heater, that squeezing effect can be thought of as a multiplier for the heat “pulled” out of the air. The chemical in our pump is propane, and it’s boiling point is -42°C, so basically, our heat pump works well even if the outside temperatures would kill a mammal like us.

The heat pump does have a back up plan, for when the “flow temperature” being generated is lower than the one needed to heat your water or rooms, there is a back up electrical heater.

Which is the point of this post.

Finally! Which is what, please?

When the ASHP was installed, it was given some settings to describe how it should behave.

For the summer, the maximum flow rate (or the maximum temperature coming off the compressor) was set to 50°C, which would work well for us, if we weren’t trying to use our house as a heat store.

We bake the house at midday and, fundamentally, only heat our hot water once a day. As we have solar cells, our time of day is midday’ish – I shift the time based on our house’s solar elevation (I talk about solar elevation on 14th February 2026).

What?

We get free solar engergy off our roof (well not free to install, but we bought the panels many moons ago, so it is free now). Plus, our solar energy is definitely carbon free (their carbon debt being paid off back in 2016, please see Number Crunching Part 1). Making the most of that energy is really important to us for those very reasons – keep our costs down and our CO₂ emissions to a minimum.

OK, I’ll bite, is this your only option?

We could sell that back to the grid and then buy back energy later in the day. But our rates don’t change: Ovo’s Simpler Energy Plan has a low standing charge, so while the units are a little higher than other plans in Ovo’s range, we benefit during the summer when we’re effectively off-grid.

Which all means that our heat pump is not working for us as well as it could for these reasons.

Why is that?

The coefficient of performance (COP) for our heat pump is around 4.1 per annum, that means for every kilowatt hour of energy it consumes, it produces four point one kilowatts of heating. Basically 1kWh = 4.1kWh. That’s made of the electrical heater and the compressor.

The electrical heater has a lower COP, about 1. Our best strategy is not to use the heater unless necessary.

Yet, when I looked at the figures that was exactly what was happening! So far (today is the 24^th January), we’ve used 734kWh in the compressor and 50.4kWh from the heater, so far for January 2026. Why?

Well, the heat pump has a setting called “maximum flow temperature”, which has a little leeway, but it states how much of the flow temperature comes from the compressor. Ours, like many set in the UK, was set to 50°C. Everytime we try to heat our hot water up to 55°C once a day, the electrical heater was being activated. For at least £13.10 worth of electricity, that we shouldn’t need!

So, I’ve set the maximum flow rate to 57°C. This should allow us to get to our 55°C easily without needing to turn on the heater. We could set the max flow temperature all the way up to 65°C, but that might get the compressor over exerting itself at times, and I don’t mind a fiver or so spent to keep everything working well.

Is it really going to make that much of a difference?

Let’s look at last year, if you remember, we can have a look at the way our heat pump used the energy it consummed.

	Total in kWh	Compressor in kWh	Electrical Heater in kWh	Heat generated in kWh
Nov 2024	544	509	34.5	2,330
Dec 2024	603	585	18.5	2,640
Jan 2025	926	863	62.5	3,390
Feb 2025	686	653	32.7	2,720
Mar 2025	486	463	22.9	2,010
Apr 2025	187	183	4.5	1,010
Jun 2025	113	111	02.0	632
Jul 2025	38.1	37.8	0.3	220
Aug 2025	43	42	1	222
Sep 2025	90.7	88.9	1.8	537
Oct 2025	231	227	3.7	1,240
Nov 2025	510	493	16.7	2,130
Dec 2025	617	597	18.4	2,600
Jan 2026	1,000	940	62.5	3,440
Feb 2026	?	?	?	?
Mar 2026	?	?	?	?
Apr 2026	?	?	?	?
Total	6,074.8	5792.7	282	25,121

This is something we’re going to try until April, I will let you know how it goes, probably with a graph.

If we can reduce the power used, because the compressor is more efficient than the heater, it’s probably something we’re going to keep doing!

Is it worth it to save 122.6kWh between January 2026 and April 2026?

From a money point of view that’s 122.6*£0.26 ~ £31.88. Is it worth the squeeze? But if we can reduce our CO2 levels further, it’s got to be worth it, hasn’t it?

Breaking the 80% Ceiling of current diabetes technology.

For decades, the clinical approach to insulin replacement has treated the human body as a predictable, linear machine. Standard “Total Daily Dose” (TDD) and “Basal/Bolus” ratios operate on the assumption that if a specific amount of insulin is delivered, a predictable result will follow. While early insulin pumps introduced distinct profiles for weekdays and weekends, and modern Hybrid Closed Loops (HCL) now react to real-time sensor data, these systems remain fundamentally limited, based on reactive responses to basals that rarely change.

Most current HCL users hit a “plateau” of 80–85% Time in Range (TIR). This is because these systems are reactive; by the time a sensor detects a glucose excursion, the physiological event—whether stress, hormonal shifts, or delayed digestion—is already in progress. They are chasing a moving target using a linear lens to view a chaotic biological system.

Embracing Chaos: The Attractor Model.

Drawing on James Gleick’s Chaos Theory, we must recognize that diabetes is a dynamic system where small variations in initial conditions lead to vastly different outcomes. A “standard” Tuesday basal rate may fail on a Tuesday where the user is stressed, at a different altitude, or at a specific point in a menstrual cycle, or a storm is brewing changing the environment in which the pump is operating.

In 1997, I began conceptualizing a model that moved away from “averages” toward a framework of attractors. In this framework, an attractor is any quantifiable influence, such as altitude, barometric pressure, or site location, that pulls the metabolic system toward a specific state. Instead of viewing these variables as “noise” to be filtered out, my framework treats them as deterministic pivots that shift the system’s equilibrium.

Quantifying the “42 Factors” with 2026 Technology.

The 2018 publication of the “42 Factors That Affect Blood Glucose” by Adam Brown provided a taxonomy for these influencers. However, the real breakthrough lies in our ability to quantify them in 2026 through the ubiquity of wearables and the Internet of Things (IoT).

By utilizing a smartphone as a central processing server and wearables (watches and sensors) as data donors, we can establish individual “biological signatures” tied to the person with the pump. We no longer need to guess the impact of laying in bed, a commute, or an intense exercise session; the hardware provides the high-resolution data streams (accelerometers, temperature sensors, GPS) to establish these values in real-time.

The Core Logic: Predictive Tailoring.

The framework operates by taking a personalized “base” basal rate and modifying it through a cumulative total of active attractor coefficients.

• Environmental Attractors: data such as temperature, altitude, and barometric pressure are pulled from the internet and localized to the user’s environment. These may impact the user or the equipment.
• Physiological Attractors: menstrual cycles, amount of sleep, or activity types, stress levels, and illness are mapped via calendars and biometrics.
• Decay Factors: the model accounts for the “lag” or “tail” of certain events, such as the lingering metabolic effects of long-distance cycling or the degradation of an insulin infusion site over several days. Even the degradation of the insulin in the pump.

By multiplying the base rate by the sum of these active attractors (which may be positive, negative, or zero), the system suggests a predictive basal rate for the next 24 hours. This moves the HCL from a reactive “safety loop” to a proactive, contextual model.

Safety, Autonomy, and the “Human in the Loop”.

A critical component of this non-linear framework is user autonomy. Unlike current “black box” systems that make decisions in secret, this model suggests a “sane” value to the user, who retains the power to accept, modify, or ignore the suggestion.

Furthermore, to prevent the risks of cross-contamination, especially in households where multiple people may require insulin replacement from a primary carer, the framework utilizes a physical cable connection for uploading basal rates to the pump. This ensures that the specific attractor model and pump ID are securely encoded to the correct individual, eliminating the risks associated with wireless interference or signal crossover.

Conclusion: A Unified Path Forward.

By unifying the “42 Factors” into a dynamic, nonlinear framework, we provide the Hybrid Closed Loop with the context it currently lacks. We can finally account for the pre-menopausal woman’s cycle, the athlete’s recovery, and the traveler’s changing environment. This is not just about better mathematics; it is about reclaiming autonomy and achieving results that finally break through the linear ceiling and coping with the mistakes non-contextual hybrid loops make across the world.

Transparency Note: This post contains affiliate links to energy partners like OVO (marked with [Ad]). If you click them, I may earn a commission. I am sharing my personal data and journey as a homeowner; please remember that energy performance is highly specific to each property. Individual results will vary [AD].

I’ve obviously had some time recently to get into the nitty gritty of our heating system, tuning the heat pump settings to match the weather conditions. Not the sort of thing that people usually do with their heating.

Up to a point, I have been interested in how it all works, but my driver is to reduce our carbon footprint: which has largely been achieved just by letting things run.

Isn’t that enough? Can we talk about something more interesting, please?

Bear with me, this is interesting to some.

From our figures, the heat pump did save us money without anything more. But, what if it were more marginal than that? What if we had to tighten our belts? How do we do the best that we can? How can we keep the heat pump running as long as it should do (with proper servicing)?

I have to say, the window figures and their payback were a bit of a shock. I am sitting here with it 4°C outside, feeling very cozy and having spent only 10.6 kWh to feel that since midnight (overnight it dipped to 2°C). The heat pump buzzed along happily, ramping up for when we got out of bed.

Air sourced heat pumps (ASHP) are very different to gas boilers, as heat pumps like “humming along”, having periods where they can flex up and gently ramp back down. Gas boilers are a bit happier to just switch on and off as required. To save money, switch the gas boiler off for a bit, let things cool down then heat them back up when you want more heat.

ASHP efficiency is all about the ambient air temperature. We’ve positioned ours to take advantage of the morning sun, which helps take the edge off the frost in the air around the pump. More importantly, we’ve tucked it into a sheltered spot to protect it from the prevailing south-westerly winds and the infamous East Anglian ‘lazy wind.’ By blocking these winds, we reduce ‘wind-chill’ on the unit, which prevents the pump from having to work harder or entering its defrost cycle more often than necessary.

Heat pumps work by extracting heat from the air they draw in, so when the wind is blowing directly into it, it struggles to pull out as much heat. Think of blowing on the skin on the back of your hand, that air is colder than the surrounding air because it is being forced directly on to your skin – this is a similar principle.

Tuning the heating curve.

The other thing I’ve started doing with the heat pump is changing its “heating curve”. This is the temperature it tries to get the “flow temperature” coming out of the pump for any given input temperature.

If we had underfloor heating everywhere, a heating curve of 0.7 would likely to be a perfect heat curve when teamed with the Tado™ smart room thermostats and smart TRVs on the radiators. Unfortunately, our upstairs circuits are all radiators, and some aren’t really big enough for the rooms they are in (we have plans to swap them out in the summer). So, on a warmer day, like today, I find that setting the curve to be 0.8 works for us. During colder days, we find a heating curve of 1.1 is more suitable to keep us comfortable.

 

The heating curves we’ve used over the past seven days.

The heating curve sets the water going into the underfloor heating pipes and the radiators. At warmer temperatures, the heat pump sends cooler water to these pipes as it doesn’t need to bring the rooms up to temperature in the same way, it is not fighting the temperature against the thermostats but working with the environment.

So, why not just set the curve to 1.1 and leave it there? Well, if we did that, we’d use much more energy and it wouldn’t allow the heat pump to coast when everything is a bit warmer. At the moment, having switched it from 0.9 last night to cope with a drop to 2°C, we had the pump coming on earler and harder over night, but is now gently working, keeping everything warm without much effort.

We do not allow the house to get cold, even when it is resting, the pump is running very gently. As I’m typing this at noon, the pump is pre-heating the house for when the sunsets. We’ll run this way until April, when the batteries from our solar generation will start to earn their keep again. Last year, we spent very little on electricity for our heating and hot water between March and September. Over the summer itself, between June and August, I will turn off the heating circuit completely as I did last year.

What about when you leave the house?

Well, unless we’re away for a number of days, it is not worth switching off for a few hours. Allowing the house to get cold does not save us money. Indeed, I am using the house as a thermal store for our energy.

So it’s a different way of looking at the seasonal problem, in the UK?

Pretty much. And so much cheaper, in terms of power used, than the gas boiler. Remember, the best we ever did was 12.9 MWh for the gas boiler compared to 3.9 MWh for the year with the heat pump. And that was before we started actively tuning what we were using.

When we had the pump installed, we were told to “set it to 32°C and enjoy”. We’ve running it between 21°C and 25°C (which mirrors our rooms thermostat settings) against variable heat curves. We’re more than enjoying it.

Can I be honest, here? I love data: I am a bachelor of science even though I did maths and computer science, and some of my natural scientist friends do look down on that “type of degree”. Can I be honest, I do think maths is more of an arts subject, as we don’t tend to do experiments.

Computer science is arguable. Yes, it is language based, but the vast majority of coders do test their code to ensure it is doing what it should be doing…

That’s not why I’m writing this piece. This is all about getting an infra-red camera.

Why, oh why, would you bother writing about that?

Well, because it’s kind of fascinating. We all know what we learnt at school and from the various adverts and articles discussing how to save energy at home by “keeping the heat in” – that’s insulation to you and me.

But as a mere human, it’s very hard to know if the measures you are taking are making any difference.

Without measuring, of course. I could have bought a dedicated unit: instead I bought a dedicated charge-coupled device that doesn’t have a filter to cut out infra-red rays. It plugs into the USB C port on my phone which launches the app which can display the data (image) being captured by the camera.

It came first thing this morning and I had a busy day at work, so I wasn’t able to play with it until my afternoon tea break. Oh my, it is amazing.

Downstairs, we don’t switch off the heating during the day, turning down the thermostat to 16°C. Internally, where we get thermal gain from our windows, the floors and furniture are warmer than their surroundings.

Externally, that heating effect is heating bricks that take much longer to cool down – so taking pictures at 7pm, 2 hours after the sun has set is probably showing heat coming off the bricks that is completely expected! If I’m keen I will get up early tomorrow when that effect will be minimal. Then I should be able to see if our insulation is being effective.

Some things are really interesting – if we don’t wear slippers, the camera picks up where we have just walked. Our footprints glow white then fad to yellow, orange, red, then fade completely.

We can see the heat conducting and convecting off our radiators or pouring through the underfloor pipes. We now have a means to see where our heating pipes are, so long as we’re pointing the camera at them when they first come on.

Outside, we can see the heat pour from the air vents in our walls and windows. The garage is particularly lossy, not least because it is very difficult to make it air tight. It also has the pipe work for the heating and hot water. We, and the previous owners, had lagged much of the pipe work in there as a result, but of course we can see if that is being impactful. The gaps are obvious.

But mostly, it looks like it is all working reasonably well.

So, how do you make use of the camera, and understand the results?

Good question. The camera calibrates itself to the surroundings, which means the scale is shown each and every picture.

Take this one of the lounge floor just starting its heating cycle just after tea.

The dark areas are cooler than the white areas but scaled for the image in question. Another picture will be at a completely range.

You know that advice to not dry items on radiators. This is why:

The radiator is nice and warm, but the towels are just soaking up all that heat and not distributing it around the room.

The tiles are colder, 21.2°C – the dark colour is not a good sign. It means we’re probably losing heat through this interior wall.

This picture shows that little heat is being lost through this external wall. While the window vents and wall vents are leaching heat through them. My beloved is glowing bright, as his body temperature is about 36°C – it was a little cold out in the dark that night and his clothing is shielding it a little.

OK, so now what? What are you going to do with this “knowledge”?

Well, nothing today, per se. But, it has spurred us into getting a blind for the last uncovered window in the house – a thermal black out one, of course.

I am very tempted to get something for our internal doors – it’s frightening how much of a rooms heat pours into the hallway.

We also seem to have some gaps in our roof insulation. We need to ensure this is breathable insulation but it’s tempting to pull our finger out and close those gaps.

Of course, that will all help to reduce our carbon footprint and save some money. It’s been a cold autumn. Even so, we are using dramatically less electricity to heat our house than we used gas – how can I say that? Well, a low usage year for our gas consumption was 13 MWh, where-as we have only used 3.97 MWh last year.

Of course, now the windows have been installed, I am looking forward to seeing the new results.

The results with the new windows.

What else can we do with this kind of knowledge?

Of course, this is not the only thing we can do with the camera.

The temperature measurement means I have been able to tune our heat pump to run really efficiently.

Heat pumps are basically mecahnical compressors taking heat from their inputs and use an exchanger to heat the water for your hot water supply and radiators and/or underfloor heating circuits. Compressors work efficiently (both economically and in terms of longevity) if they run gently, running at a constant rate and temperature.

So, ideally your input flow to your radiators is hitting about 35°C-50°C. By the time it hits the last radiator in your run, you shouldn’t be losing more than 5°C – you can only know that by measuring it or painstakingly working out the gradient from the radiator thermostat graphs and deriving the differences between each of your radiators…

Anyway, I used the camera to see that we were dropping about 10°C across our upstairs run, meaning our last radiator is struggling to get up to temperature with a input flow temperature of 42°C. Looking up how this works (Google or Gemini are your friends here), our strategy has changed.

First, change the temperature levels.

Our pump has three settings. Reduced will be set to 22°C, Normal to 23°C, and comfort to 25°C.

Next, look at the heat curve.

Our pump was originally set to “0.7”. That works really well for our underfloor heating circuits, but the radiators did not get up to temperature unless our temperature levels were set to 23°C, 25°C, and 27°C!

I have reset the curve to “1.1”, this changes the flow temperature that is set once the outside temperate (the ultimate input for the heat pump, the air temperature is where the heat is being extracted from). With a curve of “1.1”, the flow temperature going in to the radiators is set at 50°C when the outside temperature is below 1°C. At 10°C, the flow temperature is 40°C, and 20°C when the outside temperature is 20°C.

Finally, timing which radiators come on when.

Our ensuite tado radiator needs to be on most of the time, as that means the radiators in the 2nd ensuite and the bathroom are on. So, during our heating window (when we’re making the most of our solar generation), it comes on for an hour longer than the other rooms.

So far, it seems to be making a difference. Our electricity usage curve has smoothed out. Of course, I am mucking about with this on the coldest day of the year!

Now, what you are looking to do is keep your rooms at a reasonably constant temperature during the peak times and let them gently cool down when electricity is at its peak charge rate.

During the summer, we will be using our solar panels to heat our water completely, but spring and autumn will see us use the house as a thermal store, so we can move off using the grid as much as possible.

The winter is all about being comfortable. Last year, January saw us using 1,327.00 kWh, with 926 kWh being used by our heating.

Now, there are some things we need to consider. Our radiators worked well for a high output boiler, but we have to tune our heat pump to suit them. Ideally, three of our radiators would be swapped out. Looking at the camera and the electricity usage, it would be worth doing that for the bathrooms. Next week I will be looking at some tuning we can do for our heat pump, given these insights!

Hope this gives you some thought on your planned setup for your heat pumps or boilers!

Last week, we looked at the cash return on replacement windows, which, on the face of it looked marginal at best. But of course, we have made other investments over the past twelve years.

Easy steps, let’s look at the LED lighting.

About a year, just in saved electricity. Initial cost was about £350 for the whole house, and the kitchen lights alone (£250) paid for themselves in three months.

What about the solar panels?

Our panels cost circa £6,000. With the SEG and FIT, and the money they have saved us in terms of not having to buy electricity, they paid off in about 5 years.

The tado heat controls.

Like the lights, a chunky cost, incurred back in 2014 and 2015, over six months, but around £750 for our eight smart radiator valves and five thermostats, and one hub. The radiator valves were the initial step and proved themselves, so expanded the system to the whole house.

These allowed us to go from using c. 17MWh in gas a year to c. 14MWh in gas a year, just when gas prices trebled. So, two-three years to pay off.

Can the same be said for the heat pump?

From Number crunching part 2 we can see the power used to heat our house has gone from 13,270.888 kWh to 3,966.20 kWh – we’re going to pretend we have bought this electricity, just to keep the numbers simple.

At today’s prices, gas is £0.0603, so the gas would have cost £800 and a standing charge of £0.35 per day, so annually that’s £928.

The electricity has already had its standing charge paid for because we need the fridge power, lights to come on when it is dark and to be able to cook our food – we only pay that charge once. We’re not using gas for anything but heat and hot water.

So, at £0.2527 per unit, our heating has cost £1,002.26 – if we’d paid for it all. But we didn’t, during the summer, a good 750 kWh was used straight off our solar cells or batteries. So let’s run that again, giving £812.73. Which is cheaper than the gas per annum by £115.27, so in hundred years, or so it pays off. Our boiler was dying anyway – a new boiler would have cost £7,000 (it’s a big house, it needs a big powerful heat pump or boiler, many houses do not need as much capacity) – so should we say the difference is what we’re paying off? In which case, 43 years!

I suspect we’ve spent more than we needed to, as we punched big holes in to our house to do the renovations back in the tail end of November 2025. I’ve also learnt a great deal about how to balance what we’re generating against what we’re using.

Of course, without the smart radiator valves and thermostats, it would have been a different story. Without the fabric of the house being well insulated, it would not have come in as quickly either.

I’m cheating a little, because we already had the solar cells – we were about 35% self-powered last year for everything, including our car. We don’t have to pay twice for the standing charge.

Buying our new windows should help accelerate that period.

But I think that is a good way to look at the total cost and pay back period. This wasn’t a big bang but a series of smaller steps.

In the East of England, we have an “artic airmass” causing freezing weather. It’s 2°C out there at the moment, and has been as low as -6.5°C in our bit of the world over the past couple of days.

So, what is it like living with an air sourced heat pump in this climate?

It’s fine. Obviously, outside is chilly. But the house is maintaining its heat and the heat pump is working well. At 1°C, we’re getting a coefficient of performance of 11.5kW / 4.05kW = 2.84. In other words, nearly three times as much heat out of the system for each kilowatt consumed.

So, it is still out-performing a boiler.

We’re still getting some energy out of our solar panels – the pitch of our roof and the orientation mean that the snow melts well. That meant that yesterday, we got 5.1 kWh, and today we generated 3kWh.

Our daily consumption is quite high for heating. Yesterday, we used 58.8kWh for heating. Today we used 60.5kWh! During June 2025, our entire consumption for the month was 43kWh and that all came off our roof!

But, we’re sitting quite pretty. Our battery is carrying a little extra power, so if there is a power cut, we can keep warm for a little while. We also have a wood burner, if needed.

But so far, it all looks good. Hope you are keeping safe and warm out there.

A question was asked after publishing Is there such a thing as breaking even? “Does the carbon cost for windows repay sooner or later than the financial cost?”

I am going to find that a difficult question to answer, as we had some substantial building work done to put in a French door and take out a window and a French door on opposite ends of a wall and have a single big patio door put in.

So, let’s having a look at the energy saving compared to the old windows against what we can expect given the u-values for the new windows.

A quick reminder of what a u-value is: u-values are the rate at which heat is lost from a surface and is dependent on a few things such as materials, air gaps, and is measured in Watts per square meter a degree Kelvin or W/m²K. (Kelvin’s are used here as they are the scientific unit (also known as the SI unit) for temperature, unlike the Celsius unit and you then don’t need a pesky ° symbol when typing this out). The lower the u-value, the better.

From the previous article, we know that the temperate loss for the new windows will be, so we’re looking to compare that to the old windows. Some people who’ve studied this as part of their day job work this out to be: Annual kWh Savings = (u-value of old window – u-value of new window) * area of the window in question in m² * “Degree Days” * 24 / 1000.

The first three terms of this equation are explained in full in the equation! The “24/1000” converts u-value into kWh. The “Degree Days” is a new term here and refers to the average temperature for the location in question. A good source is the Enman degree day data, which show how much a building needs warming up and cooling down based on the external temperatures. In the south of England, that’s approx. 15.5°C and can be sourced from the https://www.degreedays.net/#generate site or https://www.gov.uk/government/collections/digest-of-uk-energy-statistics-dukes. Of course, from the last post, you can see the UK is a properly seasonal place…

I hate to say this, but a spreadsheet is our friend here.

Window	Area m2	Old u-value W/m2K	New u-value W/m2K	Degree days °C	Annual saving kWh
Spare room north	1.019	5.8	1	15.5	2.199
Spare room south	1.019	5.8	1.1	15.5	2.419
Master bedroom	3.500	2.8	1.4	15.5	5.104
Ensuite (estimated area)	1.000	5.8	1	15.5	2.158
Bathroom	1.019	4.8	1.1	15.5	2.002
Sam’s office	1.019	2.8	1.1	15.5	1.168
Jon’s office	1.019	2.8	1.1	15.5	1.168
Landing 1	1.019	2.8	1	15.5	1.062
Landing 2	1.019	2.8	1	15.5	1.062
Kitchen doors	3.471	2.8	1	15.5	3.615
Kitchen by doors windows	0.819	2.8	1	15.5	0.853
Kitchen south not sink	1.650	2.8	1	15.5	1.719
Kitchen south by sink	0.984	2.8	1.4	15.5	1.435
Lounge French doors	3.374	2.8	1	15.5	3.514
Lounge windows by French doors	1.649	2.8	1	15.5	1.718
Lounge patio doors	3.488	2.8	1.4	15.5	5.086
Gym	1.586	4.8	1	15.5	2.831
Cloakroom	0.643	4.8	1	15.5	1.148
Grand total					40.261

This is just plugging in the values in the table and getting the annual saving, then adding up the total.

The old u-values are estimated – a 2009 window is between 2.6 and 2.8 W/m²K, where the windows were failing, I have made them 4.8 or 5.8 depending on the level of failure. The ensuite windows are an estimate – these are shaped windows positioned in an opened area of roof. We know they were leaking.

Basically, the savings per annum in terms of power are going to be 40.261 kWh. Which is £10.47 per annum at £0.26 a unit. I could have used a different number for the old u-value, but mostly the windows were just about still working.

So, does it cost in quicker in terms of financial cost depends on how much the windows have cost and the cost of electricity or gas. The lower the u-value, generally, the more expensive the window. As you can see here, we had many windows being done! And that doesn’t include the building work.

What we are seeing is much better heat retention in the rooms where things were really bad and in every room, the energy needed to lift the temperature in the room is much less – in our bedroom, we’ve turned down the thermostat to make it more comfortable. In the spare room, where the windows were completely blown, the room holds its temperature beautifully. For us, with our EPC B rated house, this is more impactful than for someone in a house with badly insulated walls, floors, ceilings, and rooves. It should mean we retain our thermal envelop.

It’s also much quicker to vent the rooms, due to changing how the windows open, and significantly more light comes into the rooms.

But basically, it is going to take us a while, based on these values. And it is only worth it if your walls have a good u-value too, otherwise the heat leakage will come through the lower insulated path…

I’m tidying this up as I am sitting with the outside temperature hitting -2°C with the heat pump barely ticking over, so I think it’s been worthwhile.