Liz lives in The Meadows, in one of the eco-homes that were completed in 2015. Andy went to visit her to talk about the practicalities and impact of the energy saving devices that she has had installed in the house.

Thanks for inviting me into your home Liz. Can I start by asking what brought you here?

I used to live in West Bridgford but after the children left home and my husband died I decided to downsize and move here. I’d always tried to live sustainably and so the idea of living in an eco-house very much appealed to me. I wanted a house that was future proofed as much as possible, and these are built to a really high standard. I also knew that if I was going to live in a house that's ecologically sound, and these have very good insulation, are triple glazed, have fresh air heat exchange units, and are really warm, that I was going to have solar panels on the roof. I factored those into the cost of the house and they were installed the year I moved in. The house is south-west facing and there are sixteen panels across the whole of the single pitch roof.

I presume that they weren’t cheap to have installed? Do you think they have saved you money? Was that part of your thinking?

They cost me £7,000 to have them installed and I've nearly made the money back over the ten years that I’ve had them. They’ve provided me with a lot of energy and for most of this time I had gas central heating so my energy bills for electricity were very low. There was also the feedback tariff from the government, so I was given money for any energy I put back into the grid. These panels are self-cleaning so the only maintenance on them has been to have them netted around the base because pigeons were nesting underneath, causing potential damage to the cables of the panels.

In 2018, Meadows Ozone Energy Services (MOZES) working with the EU Sensible Battery project, through the University of Nottingham offered me the opportunity to have a battery fitted to the side of my house. It was a U.K. initiative, working with Tesla, who wanted to run an experiment to see how batteries could store energy from solar panels in a domestic setting. I was offered a six-kilowatt, first generation battery about the size of a door. It was free on condition that Nottingham University could do some data collection by installing a meter in my house to read all of my electric energy usage and see how the battery worked in conjunction with the panels.

What's the advantage of having a battery?

The solar energy that is generated by the panels in the daytime is fed into the battery, up to six kilowatts, which means that you can then draw from the battery later on, when it’s dark with no solar gain. The house could then continue to run on the energy stored in the battery.

I was under the impression that the power from the panels went straight into the grid anyway.

In my case the energy from the panels constantly tops up the battery. When that’s full and the house does not draw down energy, then the surplus goes to the national grid. The houses at the Trent Basin, built with a similar spec to this, have their own community battery (which at the time of the installation was the largest in Europe). All of the houses have panels and they feed their energy into the community battery.

Is data still being gathered?

No; it was only for eighteen months. Nottingham University came back, took their meter away and gave me the battery, free of charge.

My mum has solar panels and every so often I have to take the readings for a feed-in tariff. Is that different to what you have then?

No. If I produce any excess energy that I don’t use, or which isn’t stored in the battery, then it goes back into the national grid, and I get some money for that. I also have to do a reading and every couple of years they come to check that I’m being honest. When the scheme first started the government gave a really good return on each unit but as more people started to have panels the return was reduced.  So, it makes even more sense economically to have a battery now and store as much of the energy as possible. Throughout the summer I had no need to go into the grid at all. All I had to pay was the standing charge for my electric meter, the rest was free energy from the sun, gathered through my solar panels.

(The feed-in tariff scheme ended for new applicants in 2019, although those like Liz and my Mum still receive it. There’s more about the scheme here.)

How long will the battery last?

I don’t know; but like all batteries there’ll be a point where it’s no longer efficient. By the time the next generation battery is available, it’ll be smaller and more powerful.

Although this two-minute film is from Australia, it clearly explains the connection between solar panels, a battery and the grid.

So those are the panels, how about the air source heat pump? Where did the decision to get that come from?

As I mentioned I’ve always been interested in ideas of environmental sustainability in my own life and in having as small a carbon footprint as I can. As a listener of news and current affairs I’ve developed a bit of climate anxiety, like many of us I guess. I’ve always had an allotment and tried to be as self-sufficient as possible. I’m a director and volunteer for Waste Nott,  a zero-waste shop in Sherwood, and my younger daughter is the lead on sustainability for a big European company. I do like to travel though, so I probably use all the carbon I save by doing that!

I was determined to get rid of my gas boiler and be carbon neutral. So, when the idea of an air pump was mooted, I thought I should give it a go; especially in a house like this which is so well insulated. It just so happened that my boiler conked out at the same time I’d arranged to have an air source heat pump installed by my energy company. The pump is out in the back garden and runs off the energy system in the house.

How easy was it to get that installed?

It was a big commitment, and I chose to let my energy company, Octopus, manage the whole process. They seem really invested in helping people get the best and cheapest deal they can from green energy; their processes are straightforward and all their engineers are specially trained for heat pump installation. Initially, a surveyor came out to assess whether or not it would be cost effective and whether or not planning laws would allow it.

So not everyone can have one?

Well, that depends on where your house is. I’m in a conservation area so had to have a Certificate of Lawfulness to allow me to put the pump outside my house. There are also conditions around how close a pump is to the living space of your neighbour. It’s best to check with your local authority if you are interested in the idea of having one; or your energy company can do that for you.

For current information on planning requirements (and in many cases planning permission is not required) have a look at this.

How loud is it?

It’s on now; I can tell because the foliage around it is fluttering! You can’t hear anything because we’re triple glazed but if I open the door, it sounds a bit like a microwave.

Is it a big job to have the pump installed once you have any permission that you might need?

Yes; because it's not just the air pump. The pump sits outside of course but you need a hot water storage tank along with a header tank for showers and domestic use, a separate tank that supplies the radiators, and all the pipework in-between. So you need to have space for that. The tanks aren’t small; they’re thinner say than the old immersion tanks, but they’re taller as well. The radiators also have to be bigger as the temperature of the water produced through the air pump is lower than that of a boiler, and so you need a greater surface area to be heated (the average air source heat pump temperature for radiators is 35 to 45° Celsius). Then you also get this app that tells you that everything is working and that keeps an eye on the temperature so it knows when you need a little bit more heat.

There were six engineers who came to do the installation. They were here for four days; electricians, plumbers and the chief engineer who designed where everything should go. The house was very cold as the boiler had stopped working two weeks previously and it was late March. The day before they finished the chief engineer came to me and said, ‘right, we're ready to commission the heat pump; give me forty-eight hours and we’ll have this house nice and toasty’. And he was true to his word; it went from stone cold to twenty-one degrees. And it stayed at twenty-one degrees throughout the summer.

How does it work?

I’m not sure I’m the best person to ask but it’s like a reverse refrigerator. It takes air in, compresses it and turns it into liquid. The friction in this process increases the heat of the liquid which goes through the pipes and into a cylinder which then heats my radiators.

For an explanation of how Liz’s pump works look at this.

The temperature stays constant throughout the summer, at whatever level you have set it, and so if its too hot you open a window. That may seem strange, to let energy flow out of the house, but the energy has come from the air, and the energy to run the pump is coming from the sun, either directly from the panels or from the battery.

It sounds like a really expensive process.

Well, if I had to replace my old boiler with what I had, which was a premium combi-boiler, then that would have been around £3000. I was quoted £11000 for the cost of the pump and installation and the government gave me £7500, which means it only cost around £500 more than if I’d had a new boiler. Only now my hot water is free.

The Boiler Upgrade Scheme (BUS) supports the decarbonisation of heat in buildings. It provides upfront capital grants to support the installation of heat pumps and biomass boilers in homes and non-domestic buildings in England and Wales. Grants of £7,500 are available for air source heat pumps (ASHPs) and ground source heat pumps (GSHPs), and grants of £5,000 are available for Biomass boilers. More information is available here.

I then had to pay a bit extra for this little contraption, which is called an Eddi. It’s got two little antennae and picks up information to decide where to get my energy source from at any moment; from the battery, the grid, or off the panels. It’s very clever.

I presume you’d recommend people to think about an air pump?

Yes, I wholeheartedly would. You really need a well-insulated house for it to be effective. The heat given off from a heat pump is low grade heat but a heat pump is more efficient than a gas boiler since it produces three to four times as much heat as it uses in electricity. When the air pump is working full blast the radiators are warm and that's all they ever get, but the temperature throughout the house is constant. My three-storey house is triple glazed with excellent insulation, but I still needed to up-size four of the radiators. And the showers never reach that temperature where they are scalding.

So, this is for hot water and heating only?

Yes. I don’t use gas for cooking and so on the first day they came to start the work they took away my gas meter, disconnected the whole thing and took the boiler out, so I don't pay a standing charge for a gas meter, which is about £20 a month. I have no gas supply to this house; it’s been tapped off, although it can always be reconnected at any point in the future.

Guess where the tanks are?

It’s a question of doing the maths isn’t it, in terms of working out whether it makes sense financially? If you have to spend a fortune on insulation and didn’t need a new boiler then it would take a few years to break even.

Yes; although people can find they spend a lot on their gas bills. It was fortunate that I'd had the whole life of the boiler, and because the grant was available this was clearly going to save me a lot of money. Of course, the insulation of these houses is also key; but because I live here, and we’ve got the Green Meadows Grant, I could have learnt how to do insulation. I’d have had the loft insulated for starters and internal cladding is doable; it’s getting much thinner and more effective.

I can tell you what my bills are since I’ve had the pump. It was installed on the 25th of March this year. March to April cost me £83, which was gas and electricity.  April to May was £46;

May to June was £25; June to July was £21; July to August, £27; August to September £27; September to October, where we are now, £37. We’re going to come into the cold period now so there will be less energy from the solar panels.

Does it need regular maintenance?

Once a year Octopus will come and service it and change all the filters in the water system. The first year is free and then I’ll have to pay. In the meantime I don’t have to touch anything. There is a master switch outside should anything go wrong. Octopus have a dedicated team of air pump installers, plumbers and electricians for the East Midlands. That’s it. I'm not expecting any issues. And my Eddi shows me what is happening, where the energy is coming from at any given moment. By the time I need a replacement there'll be something else on the market that's better and faster and quicker and cheaper. But this should last at least ten years and maybe a good bit more.

They're still building houses or office blocks with mechanical ventilation, with air conditioning; they’re still fitting boilers in brand new houses. It doesn't make any sense to me. We've known about air pumps for a long time but they have got themselves a bad reputation for some reason. I think it's about a lack of understanding more than the efficiency of the pump; it all comes down to this question of insulation. The other day someone told me about electric wallpaper which can work for old houses that don't have a cavity wall. We know that domestic energy use is something that needs looking at and presumably more ideas will be coming down the pipeline. But right now an air source heat pump for this house is the perfect solution, especially with the panels and the battery. And it means I am carbon free and doing my bit for the environment.

More information on heat pumps can be found at the following two websites:

Heat pumps explained: experts answer your questions - GOV.UK

https://energysavingtrust.org.uk/four-heat-pump-questions-clarified/