Now that climate change is inarguable, we all will need to make changes to our lives. That means actions at an individual level, though to have enough impact there will need to be collective action backed by legislation. For most of us in the UK the largest contribution to climate change is through heating our homes, and legislation will be needed to address that in time. There is legislation in place for new builds from 2025, but for existing houses nothing is, as yet, planned. However, the net zero target must inevitably create restrictions on the energy used to heat older homes. Individual action will help but we all will need to make changes if there is to be any effect on climate change.
The debates at national and international level are all very well, but what does that really mean for individuals? What significant action can people take right now, what will be the personal costs, and how can those actions be facilitated? Despite the high level aspirations, there seems to be little in place right now to encourage individual action. So what can individuals do now on some of the bigger elements such as heating our homes?
At some point we all need to move away from gas as a way of heating our homes. One answer is an air source heat pump (ASHP). They pump heat into the house from outside in much the same way as a refrigerator pumps heat out of the inside of the fridge into the room – think of the outside of your house as the inside of your refrigerator and you will get the idea. You need a large unit outside the house that has a big fan and a compressor and pipes into the house transferring heat from the outdoor unit into your heating system. Even in the depth of winter with ice and snow on the ground there is plenty heat in the atmosphere.
This all sounds very simple, but what are the challenges in replacing a gas boiler with an air source heat pump? How much will it cost? How do you find a good installer? What is the disruption involved? Will my existing radiators work or will I have to replace them? Will it be more or less expensive to run? These and many other questions occupied us until we took the plunge. This sets out our experience, and hopefully might give you some pointers.
Our house was built in 2002. It has an energy certificate rating of C and there are few recommendations to improve it. The wall and roof insulation are pretty good. The windows were double glazed, but they were deteriorating and so we have recently replaced them with higher spec windows. We have a suspended floor, which we believe is uninsulated. So, apart from the upgrading of the windows which was necessary for other reasons, we were probably as good as we could get for general insulation without huge expense.
It is a large detached six bedroomed house with a living area of 247 square meters plus a built in double garage. There are 23 radiators. We had gas central heating that kept the house cosy. Our annual gas consumption averaged 28,000 kilowatt hours. Hot water was supplied by a tank on the landing. There were some oddities with the system, like the radiators on the first floor getting warm if the hot water was on, a nuisance during the summer. We were coming to the end of the life of the boiler, and we wanted to tidy up the system. So the question arose: could we replace it with an air source heat pump?
We also have 6 kilowatts of solar panels that generate 5,500 kilowatt hours of electricity over a year and a battery that can store 6 kilowatt hours of electricity. We have a diverter so that any excess electricity over the summer is used by an immersion heater to heat the hot water – generally our gas and electricity bills from May through September are very low. Consequently our electricity bill for the year is quite low for a house that size.
An air source heat pump runs the water in the radiators at a much lower temperature than a gas boiler typically does. So the first question is, will we need to upgrade all the radiators which could be expensive? It turned out to be quite simple to test that – our boiler could be set to run the radiators at 50 degrees, the maximum that a heat pump could reasonably be expected to achieve. So for one winter we did that.
We noticed that if we went away and turned the heat off, it took much longer for the house to warm up when we got home. Also, as we were turning the thermostat down overnight we had to start the heating much earlier. Occasionally if it got below zero we upped the boiler temperature to 55 degrees, but not often. But the conclusion was that the house could be heated by an ASHP without replacing the radiators.
Then came the challenge of finding someone to fit one that we could trust. Our daughter had one fitted in a barn conversion and they had big problems as the supplier under-specified the size of the pump so their first winter was cold until the supplier replaced it (at their cost). Adequately warned we started to ask for quotes. Finding installers locally turned out to be challenging.
We have an air conditioning unit, and the supplier was well-established and did fit air source heat pumps. However, they were not registered for the government scheme that would allow us to reclaim a large part of the cost. They were very helpful, and I learnt a lot by talking them. They were very honest, but they were air conditioning engineers not central heating engineers. Their quote came in at £16,000 using their largest 16 Kw heat pump, but if we needed two for the house then it would be much more. They did not have the skills to assess the heat demand of the house, so could not size the pump for us. As there was no chance of getting a grant to support it, it seemed high but gave us a ball park figure of what to expect.
Then we had a couple of companies come and quote. One of them spent two hours in the house measuring everything and giving patronising advice. We never got the quote, but by then we knew enough not to engage them. Another seemed to know what they were doing, said we needed a full survey to determine heat demand, gave us a provisional quote of about £14,000, but insisted on a deposit before they did the survey, something we were not prepared to pay.
The third company did a full survey, and by now we were getting quite smart at asking questions. They sucked through their teeth at the large conservatory that is open to the kitchen even though it has a high spec glass roof and we did not think of it as a cold room. In the end they recommended a 20Kw system that had two pumps. Two pumps increase the cost significantly and additionally they need a buffer tank between them and the central heating system which is further cost. They said we might get away with a single 16Kw pump, but they thought that in a long cold spell the house would get cold. Two pumps raised the cost to about £25,000, but we could get back £11,000 from the renewable heat incentive. So a net cost of £14,000. We could have taken the risk of a lower capacity single pump but if it turned out inadequate the expense of upgrading would have been high.
The final survey and quote came in at £27,000 as the best place to locate the pumps was at the back of the house a long way from where it was natural to attach to the heating system. We had thought we could put them on the outside walls between our house and next door, but the surveyor said that there would not be enough air flow and we would just run the pumps very inefficiently. So we needed a 20 metre trench and insulated pipes plus ground works for the pumps to stand on.
Putting in a new gas boiler and fixing the problems with the heating was going to be about £6,000. So the cost of going for a heat pump would be £10,000 more after the government grant. We decided to go ahead, and buy the heat pumps. In ten years time if we needed to replace a gas boiler we would probably have to install one then, and the renewable heat incentive scheme was coming to an end. We said yes, and the race was on to get the job done before the government support disappeared.
The biggest disruption was the trench, but in mid February it was not such a problem as we were not using the garden. The installers said we could sort the trench with a builder ourselves, but we declined and it was wise as the installers changed some of the details of the trench mid way. All the plumbing went into the garage in the corner where the old boiler was. We chose to move the hot water tank into the garage too, which made some things simpler and gave us an extra cupboard upstairs.
So, with but days to spare we turned on our new heating system and registered for the renewable heat incentive. We had about a month of heating from it before the house started to warm up for the summer, and so we had no real idea how effective it would be. Our first of 28 RHI payment of £401 came in in July.
We then headed into winter, with all the concerns that the cost of living crisis raise, especially the cost of energy. On a short term cost-benefit we could never have justified what we did, but the driver was really how we could reduce our carbon footprint, and we could afford the up front cost. But will the running costs be much higher than with gas?
The advice was to keep the heat on 24 hours a day. All our radiators have smart thermostatic valves, so we can set a temperature for each room. The system works out how warm to make the water pumped through the radiators based on the outdoor temperature, and unless it is very cold outside they do not get hot. Keeping the heat on seems to work well, and the house is quite comfortable all day. We have had a couple of weeks of sub zero temperatures down to below -5C at night, and the radiators kept the house warm. The installers recommended we monitor the temperature and if a room was colder than needed then we could replace the radiator with a larger one – so far that hasn’t happened.
We switched our electricity to economy seven, which was 16.7p for seven hours at night, and 40.2p the rest of the day in November 2022. Given that the pump generates between 3 and 4 KWH of heat per KWH of electricity that means that overnight it is costing about 4.8p per KWH of heat, and during the day about 11.5 p per KWH of heat. We fill our battery up on the overnight tariff, and so we are getting about 40% of our electricity at the cheapest rate. That is about 8.7p per KWH of heat on average. Our gas is now 10.3p per KWH so we are saving about 1.5p per KWH, which over a typical year amounts to an annual saving of £420. That saving was unplanned and a consequence of the rapid rise of electricity and gas prices.
The other saving is through our solar panels. In the winter months our monthly generation drops to about 200KWH on average, but at 40p a KWH that is £80 a month saving over the winter. When we bought the solar panels an optimistic saving plus grant payments was £800 for the year. Now we are saving well over £1600 a year.
Is this working out in practice? In the year from 1 April 2022 we used 11,895 KWH of electricity and 124 Kw of gas (we still have a gas hob). That compares with the previous 12 months of 3992 KWH of electricity and 25,451 KWH of gas. So our electricity went up by 7,903 KWH and our gas went down by 25,327 KWH. Although years are variable in energy consumption, using this rough comparison we get 3.2 Kw of heat from 1 Kw of electricity, which is in the range suggested by ASHP suppliers.
Going forward, it looks like the system will be slightly cheaper to run than gas. The renewable heat incentive increases by inflation so we should get over 50% of our up front costs back. There is a magnified saving from our solar panels – every KWH we use in the winter is saving us over 40p now. In ten years time we would have had to make the switch. So the economics of it are not that bad. The hard thing to accept was the up front costs and the slow pay back. However if fuel costs continue to rise, the payback will be shorter; our solar panels and battery had a projected 15 year pay back when we installed them, but with energy prices today that payback is nearer to 8 years.
Considering our carbon footprint, the energy performance assessment when we had gas central heating was 4.3 tonnes of CO2 per year. An average house in the UK produces 6 tonnes of CO2 per year. We buy our electricity from a green supplier, so arguably with solar panels our house is reducing carbon going into the atmosphere now as we export over 2,500 KWH a year, though we realise that the energy we buy is not purely green at present as even buying from a green supplier we know that it is not immediately reducing greenhouse gases from the overall energy supply chain.
We are probably at the limit of what we can do economically. The conservatory roof could be replaced, but that reduces the attractiveness of the house and we enjoy the conservatory, plus when the sun shines the house is warmed even in winter. We could insulate the floor but that would be expensive and disruptive. Underfloor heating is considered better, but that too would be expensive. We could add more solar panels and a bigger battery which we may look at. We will in due course buy an electric car and when they are available we will probably install a vehicle to home charger so we can run the house off the car battery, fill the battery overnight and store more of our solar generated electricity, so we get more of our heating from low cost or zero cost electricity.
We are unusual in having a large house, and we could afford the up front costs. A smaller house would have been much cheaper to refit, and probably there would not have been a need for all the ground works. However, it looks like it will be a great success. It may take a few years to pay for itself, but it feels like the right thing to do. If we sell the house, then we expect it to be an asset now having a modern electric heating system that matches gas in terms of heating performance and running cost.
Can this scale and become feasible for all homes? Purchase costs will fall, and the availability of good installers will grow. For some time it will be cheaper and easier to stay with a gas boiler, though there will be a point in the not too distant future where overall costs converge – gas is likely to get more expensive and electricity cheaper. The stark fact, however, is that we cannot continue to heat our homes the same way we have for the last few decades. Today it is practicable but expensive to switch to electric heating, which is the first step, and if running costs are now comparable that is a major hurdle overcome. The answer has to be yes to the question can we make the change, the question now turns to how and when. What support and encouragement will people need to make the change? How will governments turn aspirations and global commitments into reality?
