‘We have no bills’: installing a heat pump in an 1850s cottage

Can heat pumps be used effectively to heat old houses? Energise Sussex Coast’s Gabriel Carlyle interviews someone who’s done it.

Heating the UK’s 28m homes produces almost a fifth of the UK’s greenhouse gas emissions – the primary driver of global warming – mainly as a result of burning natural gas to heat our homes.

The core technology for changing this is the heat pump. However, despite being the dominant heating technology in Sweden, Norway and Finland, in the UK heat pumps have been ‘the subject of hostile and misleading reporting across many mainstream media outlets’ (Carbon Brief).

At the end of September, I caught up with East Sussex resident Olivier Wall, who had a heat pump installed in his home just over a year ago.

Where do you live?

Olivier Wall: I live south of Burwash, in the countryside, in an 1850s cottage. The latter has a combination of poorly-insulated solid stone walls and insulated cavity walls. Prior to installing the heat pump our Energy Performance Certificate was rated ‘F’. We’re in quite an exposed site: south-facing on a hill. We get full sunlight all day but in the winter we get the full force of the wind and the weather.

Why did you decide to get a heat pump?

OW: When we moved here the house was fuelled by an oil boiler. It also had an oil-fired AGA cooker and very inadequate radiators. So the the warm part of the house was really the kitchen and a room or two above that. The rest was pretty cold in the winter. And the fuel bills were pretty high because the AGA had to be kept running all summer.

But the main reason we did it was that I was quite interested in renewables and modern heating technologies and how you can control these digitally. So even before we moved here, I had the ambition for us to live as sustainably as possible.

What difference has it made to how warm or cold you are in your home?

OW: A massive difference. So previously it was all warm in the kitchen, but nowhere else really. Now it’s an even temperature – or whatever temperature you want in the different rooms – and it’s constant. In our old house we had gas-fired central heating that would come on in the evening and it’d be cold during the day. With the heat pump the temperature is constant – the same temperature all day. It’s great.

And what difference has it made to your bills?

OW: Well, if you include the solar panels – which we also had installed – we have no bills.

But if we set the solar to one side, I’d say that our energy costs are probably down to about a quarter of what they would have been when we were on oil. So it’s massively reduced our bills. I mean: the main energy cost in the house was heating and this now costs us a quarter of what it what it used to.

Can you remember how much it was costing you before?

OW: We weren’t here for a full year before we had the heat pump fitted, but doing a bit of educated extrapolation our energy costs were around £3,600 a year, including the electric car. The current cost – excluding solar – is £1,000 a year.

And with the solar?

OW: With the solar we’re actually making a small net profit of about £250 a year.

But even excluding the solar we’re on a bill of £1,000 a year and the payback period for the cost of the heat pump and the batteries is about five years.

In calculating this I’ve factored in some costs from the old system that we’ve avoided. The old boiler was only 70% efficient and it was on its last legs, so we would have had to replace it and the radiators anyway. So I’ve taken out some of those costs when calculating the payback period.

How much did it cost and were you able to get any help towards these costs?

The total cost for the heat pump installation – including all of the radiators, which we changed, and a new hot water tank, but not including the batteries and solar that we also had installed – was £14,791. However, we got a government grant of £7,500 towards the installation, so the net cost was roughly £7,500.

However, the batteries and solar are an important part of the economic equation.

If we just had the heat pump then we’d probably be spending about the same amount on energy as we did before. That’s because although it’s around four times as efficient as the oil boiler and the AGA, the price of electricity is currently four times as much as the price of oil – so it sort of balances out.

We’d have got a warmer house – because it would have warmed the whole house instead of just the kitchen – and we would at last have had radiators that were the right size to heat our rooms. So it would have been a better solution but it wouldn’t have allowed us to recover the money that we spent on the installation.

What difference do the batteries and the solar panels make?

OW: It’s mainly the batteries. We use these to run the heat pump during the day when electricity is expensive, but we charge them using much cheaper electricity: we only ever buy electricity at 7p per kiloWatt-hour (kWh) instead of at the peak rate of around 28p per kWh. So that makes the heat pump four times cheaper than what we had before.

Does that mean you’re mainly charging the batteries at night, when demand for electricity is lower?

OW: We have an electric car and we’re on the electricity supplier Octopus’s Intelligent Go tariff – and that means that, when the car’s plugged in, we can often access 7p per kWh electricity to charge the battery during the day as well as at night.

What role do the solar panels play?

OW: The solar is doing its main job in the summer and the heat pump is doing its main job in the winter, so they don’t really coincide very much. But the solar helps with the car and it helps with the background load of the house in the summer. So it’ll cover the washing machine and that sort of thing and it helps with the the heat pump by charging the batteries a bit.

But it turns out that, in terms of money, exporting the energy from the panels back to Octopus is actually a better way of using the energy because they’ll pay us 15p per kWh for this, and we only ever use 7p per kWh electricity from them. So, at the moment, it’s always better for us to send the stuff back to them.

We calculate that each year Octopus will be paying us £250 more than we pay them. So we shouldn’t have any electricity bill at all going forward.

How disruptive was the installation process?

OW: The heat pump installation took about a week to install and was pretty good. There were some problems with their radiator supplier so they ended up coming back three weeks later to fit the final couple of radiators. But it wasn’t very disruptive.

They replaced all of our radiators but that was just a case of shutting off the central heating and swapping-out each radiator with a fatter one. Though that hasn’t made much difference to the rooms as the new radiators aren’t much bigger visually.

There’s been a well-funded campaign of misinformation designed to put people off getting heat pumps. Clearly that didn’t stop you going ahead. Why not?

OW: You hear all sorts of nonsense, don’t you? The same with electric cars. My view was that this is not a new technology. It’s well understood. It’s used in cold countries like Sweden and Norway. Why wouldn’t it work? Fridges work and a heat pump is just a backwards fridge, isn’t it?

One of the myths about heat pumps is that they don’t work in old buildings. How would you respond?

OW: Well, that’s certainly not been our experience. If anything, I think we got a bigger heat pump than we needed.

It’s quite a big unit – 12 kilowatts (kW), whereas most properties have sort of 5 kW (or smaller for a terraced property). So it’s double the height of a normal heat pump. For our property that’s fine, it’s just tucked away behind the garage, but we don’t run it at full capacity.

We have thermostatic valves on each radiator and the heat pump is able to adjust its operations to the demand coming from the house. So we can adjust each room to the temperature we want and the heat pump will adjust its operations accordingly. Everything is super-controllable and you get exactly the temperature you want, twenty-four hours a day. It’s brilliant.

Another common claim is that heat pumps are noisy. Is yours noisy?

OW: No, it’s totally silent. I mean, it’s running at the moment and you probably can’t hear it.

No, I can’t.

OW: It’s a little way from the house but even if you’re in the garden right next to it you can hardly hear it. It’s whisper quiet. The only noise I notice from the heating itself is the usual pump circulating water in the central heating pipes, the same noise as you get with gas central heating.

You’ve had a heat pump now for just over a year for a year. Would you recommend it?

OW: Thoroughly, yes. But I would say: be careful not to overspecify. I think we could have probably put ours in more cheaply. It’s much bigger than it needs to be for our property.

It sounds like you came to this with quite a bit of knowledge. If someone is interested in finding out whether a heat pump is the right thing for their house, what would you recommend as their first step?

OW: Well, it’s probably worth researching the technology so you understand it a bit.

Also, pay attention to which supplier you choose and go for a big well-known name.

We struggled to find a supplier originally. We looked into some of the smaller ones but we weren’t convinced that they’d do a good job.

We had hoped to use Octopus but they came and surveyed the property and then decided that they couldn’t install in our region – they were obviously still getting their processes sorted out.

We ended up with Aira, a Scandinavian company that has started working here in the UK.

They did seem to struggle to size the system properly though. I had to review their design – they sent me spreadsheets of their heat loss calculations and their radiator sizings and I had to interact with them quite a bit to get that right.

On the other hand, the deal we signed up for with them includes free servicing for 15 years and guarantees the temperatures designed in every room down to an outside temperature of -6ºC I believe.

When we were looking, it did seem as though the market in this country was immature. Many of the installers we spoke to were still learning how the technology worked and how to design a solution – they seemed to struggle with anything other than a modern well-insulated house – but that was nearly two years ago now. I would hope things have moved on since then.

Any last thoughts?

Before the installation starts, it’s worth considering where the various tanks and pipework are going to go – not just the heat pump itself. Otherwise, if you leave the choices entirely up to the installers, you might end up losing a bit of space in the house and or with some unsightly ducting outside.

In addition to the heat pump and the radiators, Aira also installed a heat pump compatible hot water tank in our utility room, replacing two we had in our loft. If I was doing this again, I would have insisted on putting the hot water tank in the loft. And I would also have hopefully agreed a neater solution outside the house where we have a bit more black ducting than strictly necessary. Installers will do what is easiest for them.

Do you need help working out whether a heat pump is suitable for your home? Or maybe you’ve been in contact with an installer and want help understanding the spec you’ve been sent? If so then please contact ESC’s retrofit advice service: retrofit@energisesussexcoast.co.uk.

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