Potential air source heat pump running cost issue

by Mars

When we installed our air source heat pump two years ago, all our running costs and calculations were based on electricity being sold at around 15p/kWh. We’ve changed electricity providers a few times to ensure that we stay under that financial mark, but that’s proving to be more and more difficult and I think that air source heat pumps are going to be put under pressure from a running cost perspective in the years ahead.

So let’s put things in context. Before our air source heat pump went in, we were paying £250 a month in oil (at 50p per litre) to heat the house, which as we’ve mentioned many times, wasn’t economically viable. When the air source heat pump went in, we were paying 14p/kWh of electricity, which made it cheaper to run than oil.

But let’s take a look at the January numbers for our heat pump. January had a lot of really icy days and it’s been the longest sustained bout of cold weather we’ve experienced since moving in. Last month, we consumed 2,231 kWh of electricity, just for the air source heat pump, which is a crazy amount at around 72kWh per day.

Over January, we were lucky in that our Symbio rate was still 11p/kWh. That expires at the end of February, and we can’t find a provider for anything less than 16p/kWh. We don’t have a smart metre, so we are reliant on competitive set tariffs. Having said that, most people on smart metres with agile tariffs are averaging around the 15p/kWh mark in January.

So what does this mean? To answer that, let’s put our January consumption into the table below and see what it costs to heat our house based on these various rates during a cold month.

Tariff Cost on 2,231 kWh consumption

I find the numbers above a tad scary. Yes, we’ve had a cold January, and February so far is equally icy with beast from the east blizzards, and as climate change continues to throw up colder winters, I’m not sure how economically viable it’s going to be to heat this house if electricity rates don’t drop.

As mentioned, we’re super lucky that we have a low tariff for January and February, but that’s not going to last, and at that rate we were able to heat this house at £245, £5 less than what we were paying for oil.

It looks like the best tariff we’ll be able to get for 2021 is 15p/kWh and that shoots our heating bill up to £334 on January’s consumption, which is mad, and it isn’t financially viable in the long-term. I suppose we’re getting some assistance from our solar PV, and in January we generated a modest 161kWh of power. Since we’re on a tariff of 11p/kWh, we’ll apply the same value, which means we can shave off £18 off our January heating bill.

So it’s an issue for us going forward, and the issue will apply to all people with an air source heat pump, irrespective of their home size and what they’re paying for heating because it’s all relative. Everyone’s bills will get higher with more consumption and higher rates.

So I think the UK government has a problem on its hands. They are driving the market for more and more people to switch to ASHPs, but they will become unaffordable to run. Unlike gas or oil, you can’t just switch the pump off to save on heating and then turn back in when you get too cold, because theses pumps can take days to reheat cold rooms and that reheating process is incredibly inefficient.

I can’t see a feasible, sustainable, financially viable way of running an air source heat pump at tariffs over 15p/kWh and that, for the first time, has me worried. I spent the weekend on comparison websites and visiting providers directly. Most tariffs are at 16-18p/kWh and that’s going to be extremely expensive if we start to have regularly cold winters.

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