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An air source design

I swear, this April has been one of the coolest I can remember, not helped by the fact we currently have no central heating!

The boiler, rest in peace from 28th March, has been switched off, with all our water heating happening via our Solar iBoost. We’re spending 130kWh on heating the water on a planned timer ( 2 hours in the morning and 2 hours in the evening) a week. Whenever it is sunny, power is provided to the hot water tank, too.

This is compared to 400kWh a week on both heating and water last year. Quite a difference! And that’s not looking at the fact that heat exchangers (heat pumps to you and me) are typically much more efficient that other forms of heating.

But as we’re busy paying off the mortgage, there’s a big pause – thank goodness the weather is begining to warm up.

Is it cold down south, then?

There have been odd days this April, when it has been a little chilly. Oil filled electric radiators and lighting the fire has kept the chill at bay. Now the sun is shinning, despite outside being 16°C, our rooms have reached >20°C on average thanks to solar gain.

Our insulation means once the rooms have got that hot, they take more than 10 days to cool down. It’s not quite a passive house, but it is making the most of what it has.

All this is helping reduce our carbon footprint and that’s really the point of the air sourced heat pump. The the moment, though, it is nowhere near as cheap as a boiler for this sized house! Our scale is not helping at this precise moment.

Electricity is typically 0.20707kg CO2e per kWh in the UK. Gas is about 0.18293kg CO2e per kWh – so why switch to electrical heating?

Well, Gas heating is about 80% efficient, so for each kWh, we get 0.8kWh of heat.

Heat pumps are about 350% efficient, so for each kWh, you get 3.5kWh of heat.

That efficiency reduces the CO2 footprint while in use. In practice, a kWh in heat is 0.06kWh in CO2e per kWh. Which is why everyone is so keen on the idea. Our 30kW boiler is being swapped for the 10kW heat pump to give a similar performance. Teamed with the heat retention of the house, it should all be good.

We just have to pull our fingers out and get the installation booked. To avoid expensive costs, we’re waiting for my bonus to come through and the mortgage to be settled. No point in doing this on credit.

Costs of switching off the gas?

We still have our gas meter connected, although we’re not using anything. That means we’re just paying the “standing charge” – at our current tariff, that’s about £10 a month, or just under £120 per annum.

As we don’t use gas for anything else, we can lose that meter and that charge. Of course, that isn’t for free. The fee for removing the meter is £106 and it needs to be performed by the “gas supplier” – who are not the people who produce your bill each month!

Complicated, but should be worth the effort.

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