Heat pump or gas or oil?

It’s no good just working out how much per kilowatt hour a heat pump costs to run compared to, say, a gas boiler. What’s more to the point is what is the total hit to your pocket will be after a reasonable length of time. Your system might have to generate around 15,000 kW.hrs or more each year. After about 6 years that will come to a neat 100,000 kW.hrs which is handy for making the maths easier. Say you spend £5,000 on a boiler then the cost per kW.hr is 5p – we just need to shift the decimal point along. Add to that the actual running cost of the plant in question and we can get a good idea of the total long term cost. In the same way, the total cost of the energy component is also a decimal point or two away. So, say, 12p for gas is £12,000 for the 100k.

What about in the longer term when the cost of the kit is spread out? The grey bars go to 200k kW.hrs with the kit cost remaining the same, so that’s a good 10 years where the differences become even more marked.

These sums illustrate the danger of adding more kit to your mix. Follow the government lead on hybrid heat pumps and you’d add about 10p/kW.hr to your existing set up but the 100k target doesn’t move.

And here’s a graph with the results. Double click on it to get a bigger view.

Bearing in mind that the bottom scale shows your future heating bills and those figures are £thousands the differences are significant.

Electricity £1,500 – As you can buy cheap electric radiators this might have fared better, but the sheer weight of expensive electricity has made this the worst choice by a long way. £70,000 for 10 years!

Stove and tank £5,200 – A stove connected to a heat bank is expensive but fares well compared to electricity. Even better if you can access cheap wood.

Heat pumps £10,000 – The heavy up front cost and use of the most expensive fuel makes heat pumps, sadly, the third worse choice.

Battery on Go £6,500 – An expensive battery grabbing cheap night time electricity from Octopus works out well but it’s always a limited supply.

Pellet boiler £4,000 – Who cares?

Gas boiler £2,500 – Getting better and reassuring seeing that this is what most people already have.

Oil boiler and tank £4,500- Expensive to buy and install. Expensive to service. We can do better.

Mini-split and battery £8,500 – Expensive battery meets cheap heat pump and the result is magic. Not the winner here because the battery will wear out eventually. Not shown on the graph but solar + split is the way to go – this was only evident after the graph was there to see.

LPG gas boiler and tank £3,500 – Not too bad up front and cheap to run. The winner by miles and leaves you much better off than with a heat pump.

Solar £7,000 for 20 panels – Not a fair comparison with this list as it would take 10 years to make the 100,000 kW.hrs but they would cost no more than the price of the panels. So whatever you chose above, the panels will always be sort of better but you’d need them as well. Add a mini-split and that’s proper magic.

Conclusion – LPG gives plenty of power for not too much up front. Add lots of solar panels and a mini-split or two (without the battery) and you’ll be cushtie – relatively. Remember you will have electricity costs as well as all this heating. Solar panels reduce the electricity bills considerably and often run the mini split free of charge. Free aircon in the summer is a bonus.

While I hope my figures are correct please check before making any decisions.


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