So it’s a one year since we had a heat pump installed in our 1930s three bedroom semi-detached home in Chippenham. Are the myths true? Did it work on a leaky 1930s house that isn’t that well insulated? Has it cost us a fortune to run? Are the neighbours walking around with ear defenders on? Were we shivering all winter?….. read on to find out!
Introduction
So a year ago we finally took the step to go gas free, replacing our gas hob with an induction hob, and our gas combi boiler with an Octopus Energy installed Daikin Altherma 3 8kW heat pump and hot water cylinder. We had been fortunate to receive a very good price from Octopus Energy of £2180 after the government grant. This was comparable with a new gas boiler, but included far more equipment including a new hot water cylinder and six radiator replacements. You can read about the installation in my post here. It would be fair to say my wife Diana was sceptical as to how well the heat pump would work in our 1930s house, but agreed that the price was exceptional value and that we should give it a go. I realise that £2000 isn’t a figure many people have sitting around, but as our combi boiler was failing and needed repair or replacement, the timing seemed right. We both agreed that getting rid of gas was a step we should take to decarbonise. Our motivations were primarily for carbon saving. I wasn’t sure if it would save money – if anything I expected it to cost about the same to run. I was hoping it wouldn’t cost more.
One year on
So how did we fair one year on? Well you may have a slight spoiler if you’ve seen my previous post made in March this year where I looked at the winter running costs compared with a gas boiler.
The heat pump has been fantastic! The house was consistently comfortable throughout the winter months, all the time, not just in bursts as we used to have with our gas combi boiler. The radiator changes also meant that the rooms were much more consistently heated, whereas previously we’d had a cold corner bedroom.
We’ve had plentiful hot water all year. You can hardly hear the heat pump when it runs unless you stand right in front of it. Even then it’s quieter than background traffic noise. An unexpected bonus was the hot water reaches the taps and shower faster, largely due to our cylinder location being closer to both than the combi boiler was.
But what of the energy usage and what of the running costs?
In order to compare i’ve looked at the same month a year before when we were running with a gas hob and gas combi boiler. Our combi boiler was a Worcester Greenstar and we had set it up to run in condensing mode, so it wasn’t a terrible gas boiler.
The electricity tariff over the period is broadly the same. We have a Plug in Hybrid Electric Vehicle and use the Intelligent Octopus Go Tariff which gives us 7p/kWh at night and 28p/kWh in the day time.
Our house occupancy was actually higher in our year with the heat pump as we hosted a regular stream of airbnb guests which we didn’t have the prior year.
I’ve gone through our Gas and Electricity bills in detail and the headline summary is:
October 2023 to October 2024 (Gas combi boiler and gas hob)
Total Energy usage (gas and electricity) : 13807kWh
Total Energy cost (gas and electricity) : £1598.98
October 2024 to October 2025 (Heat pump and induction hob)
Total Energy usage (all electric, gas removed) : 6443 kWh
Total Energy cost (electricity): £1108.70
So with the heat pump and induction hob we used 46% of the energy and our bills were 31% lower saving £490 over the year. Pretty impressive!
I’ve put a graph of the 2023/24 gas and electric costs vs 2024/25 electric only costs below. Orange is Gas and electric 23/24, Blue is electric only with the heat pump and induction hob, gas meter removed 24/25.
It should be noted these costs are total household energy costs including occasional PHEV charging, standing charge, and VAT.
But don’t you have solar and battery too?
Yes we have a 4kW Solar PV system and a 5kWh AC battery. We also had these in operation over the same period with electricity and gas the prior year.
So haven’t these skewed your savings?
Well yes and no. If you saw my previous post covering the four winter months November to February inclusive you’ll see that the solar and battery didn’t influence our savings over the winter period as there simply isn’t enough winter solar generation, and our battery doesn’t last all day in the winter. That is, yes of course solar and battery help reduce our bills overall, but the savings made since the heat pump and electric hob were installed are purely down to the greater efficiency of the heat pump. If you like, solar and battery were already contributing to our base household load even with gas.
It’s a slightly different picture over the summer months as this year has been very good for solar and in the summer months we have no need for heating. So we have more energy than we can use. We have made some savings by running the heat pump to heat the hot water, something we couldn’t do with gas heating hot water.
Looking at the stats the Heat Pump used about 200kWh over four months heating hot water in the summer. If we consider this was all heated using excess solar running the heat pump as I describe in this post, then we’ve saved the 7p/kWh we would have used at night heating the hot water. So 0.07 x 200 = £14.
So a saving of £14. So not a significant part of the £490 annual saving! This does show how much can be saved by being on the right tariff.
Unfortunately we don’t get export payments for our solar, and though we try to use all of our excess, we’ve still exported 1Mh this year, or circa 1/3 of our generation. Most people with solar would use this to build up export credit on their bill. However we don’t receive export payments. So we could have saved a further 1000 x 15p/kWh = £150 on our electricity bill with solar export payments. This was similar to the previous year and largely down to not needing heating from the end of March to the middle of October. Ah well! We have now applied for an been accepted on the Octopus non MCS solar export tariff.
What about Carbon emissions?
One of our main reasons for switching to a heat pump was decreasing our carbon emissions. So how much have we saved?
If we consider that we’ve reduced our household energy usage from 13807kWh to 6443 kWh that is a saving of 7364kWh which it is reasonable to attribute to use of gas for heating, hot water, and cooking.
7364kWh of gas at 0.185 kg/kWh = 1362 kg CO2 saved by moving to a heat pump.
Conclusions
In conclusion we’re delighted with our heat pump installation. It’s kept the house warm with plentiful hot water and saved us nearly £500. The key to this is being on the right tariff and making best use of that tariff, for example by heating hot water at night on our 7p/kWh rate.
I haven’t looked in detail at how much the induction hob may have contributed. Whilst an induction hob is more efficient than a gas hob, we’re usually using it when electricity costs are higher. During the summer this is mitigated by the solar generation and AC battery. In the winter months our battery has usually run out by the time we’re cooking in the evening.
Overall the saving of £500 was unexpected and very welcome.
In terms of energy saving the reduction of 13807 kWh to 6443kWh is excellent, with the corresponding carbon saving of 1.3 tonnes CO2. This carbon saving will increase as the grid decarbonises, eventually reducing to zero emissions when the grid is decarbonised.
Jan Rosenow has calculated the embodied carbon in the manufacture and installation of a heat pump in a UK home as 1,536 kg CO2e. So one year on our heat pump is very close to having paid back the embodied carbon in manufacture and installation.
Would you recommend a heat pump?
Yes absolutely. For most homes it is the best path to decarbonising heating and hot water and the only option giving the efficiency savings to save money when switching from gas to electricity. The Octopus pricing structure has changed since we installed our heat pump. So whilst I would still recommend Octopus, other installers such as Heat Geek are arguably offering a more efficient installation for not much difference in price. So as with all things please get several quotes. We have listed some local installers Zero Chippenham members have used on our Home Energy Efficiency page.