Air source heat pump

[CyclingLegs]

Hi,

I wondered if I might ask what people think about air source heat pumps?

We just had a short holiday in a rental house that had one and it seemed good.

Our own house is 1920s single skin brick, detached, with external wall insulation on three sides. The fourth side is in the neighbour's garden and we plan in insulate that side internally later.

We have solar panels which produce 20KWh a day on a sunny day. We just had all our windows changed to new double glazing ones. We have loft insulation, boarded over, and the loft is doubly insulated by boxes and boxes of lego and books and whathaveyou.

The people who came to do all the insulation work all said "next you need a heat pump" and Looked At Me, and that way that means "Get on with it."

I had a man here to do a quote today, and he seems good, and all that, and I'm quite keen to do it. I just wondered if there is anything that I need to know, except where to find ear plugs, and how to tidy up a metric ton of builder's dust. Again. :-)

Thanks!

Do you actually need new heating? If you've currently got functioning gas central heating I would leave well alone for now. In five or ten years, when the boiler is on its last legs, heat-pump technology may have moved on a fair bit. I don't think being an early adopter is a good idea.

Thanks that's good to know. Our boiler packed up two or three years ago and we had a new one installed. The radiators were replaced 10 years ago, along with the hot water cylinder, so it's all pretty new really.

The previous system had been installed sometime in the era of the dinosaurs. The radiators were so large that they obscured most of an entire wall in each room. The floor-standing boiler that was really just a bunsen burner in a metal box. If we keep the current system as long as the last one was kept, we'll still have it in about 2369.

You might need much bigger radiators again if you get a heat pump.
I'd be tempted to insulate under the downstairs floors first if you have suspended floors (we are doing that room by room, from underneath).
If you replace the floor as well you will probably need 'building regs'.
Our place is 1920s, cavity walls. We're holding off on the heat pump + batteries thing for now, because we think they're currently getting technically better and still will do, though we don't have solar (yet) which makes a difference to running costs.

@hannahcolobus Thanks for this great advice. Do you know who I should consult to find out what we should do next? It's harder to do other things for various practical reasons. A bit of outside advice would be very helpful. Thanks!

I think you would be crazy to replace a 2 year old gas boiler with a heat pump.

some points :

i) Heat pumps need bigger radiators and large pipes. If you have just swapped for small radiators and microbore you will have to redo these all as well.

ii) Your solar generation is compatible with heat pumps. BUT the problem is in winter the solar generation is much less, exactly when you need the heat pump. I would be surprised if you get enough solar to run it.

iii) Your boiler is only a couple of years old and will need little or no maintanance. In 10 years time once the boiler starts getting older and worth replacing, heat pump technology will have become more established, more reliable and probably much cheaper (relatively) to fit. The performance will have also improved.

iv) Because you are unlikely to get your heat pump electric from solar, the cost of running the heat pump will not be much cheaper than gas (assuming an SCOP of about 3). Heat pumps are also very expensive to install, so make little financial sense either. Your gas boiler will be new and therefore very efficient, probably 90%+, and the new insulation will help you use even less.

What I would do is make sure you maximise your solar use. There is a gadget that allows you to heat your hot water off solar by connecting the solar to the immersion heater. This I think is relatively low cost, so could pay for itself quickly.

The other thing is to maybe get an electric car, especially if you do big mileage. This will enable you to store power, save money on petrol tax and maintanance.

Thank you very much that does make a lot of sense. We already have the gadget to heat water from solar, and we barely ever drive, so it sounds as though we are doing pretty okay.

Thanks, yes that sounds good. A man visited yesterday to give us a quote, so hopefully he will have some ideas about what we need to do.

Personally I would reconsider when your boiler is 10 years old. Technology is moving fast

We are already late in adopting heat pump tech. It has already moved past electric and gas powered water heaters.

"Heat pumps are more than twice as efficient as fossil fuel heating systems in cold temperatures, research shows. Even at temperatures approaching -30C, heat pumps outperform oil and gas heating systems, according to the research from Oxford University and the Regulatory Assistance Project thinktank." — The Guardian.

I'm interested in all sorts of green tech, but worry about the noise I hear ASHPs produce. Is this true?

But wouldn't it be great if all new housing were built with ground source heat pumps, solar panels and underground cisterns to collect rain water for toilets?

I am not a fan of stuff like this because it doesn't give the complete picture.

Heat pumps probably are 2-3x more efficient than gas boilers under many conditions. Sometimes they can even be more.

But the issue is electricity is 4x the cost of gas (less if you can remove gas entirely from your set up by getting rid of the standing charge, but not hugely so).

What's important to people is not some magic efficiency figure, but how much these things cost to run. Unless the government ups the cost of gas relative to electricity, or places some sort of tax on gas boilers the fact that heat pumps are 200-300% efficient still means they are going to cost more money than a gas boiler to run.

When you couple that with the fact that there are risks installing pumps (they may not work well with your current house infrastructure (radiators/pipework), they tend to be more expensive to install than boilers (even with the increased grant to £7.5k) and they haven't been around long enough to assess the long term reliability or maintenance charges then they look a very risky and potentially costly proposition to me. Even if everything works out OK (a big if), you are still probably not going to be significantly better off than with a boiler, so why take that risk ?

Of course if you are willing to pay more money for heating on idealogical grounds they are much better than boilers for the environment. You are also taking a gamble that the government will not try to penalise fossil fuel heating systems in the future by sticking with fossil fuel heating (I think unlikely, but possible).

Personally I think solar is a much better investment if you are interested in getting environment friendly technology. I would only consider a heat pump if I didn't have access to mains gas or had a very new house.

I'm a big fan of our heat pump. I had planned to install one anyone when we moved here but had to bring it forward once the boiler started playing up. If I had a 2 year old gas boiler though I'd only do it if I had the money and wanted to reduce carbon. Even then youd need to take into account the embedded carbon in installing new tech. Definitely something to plan for though

I will book a survey and look into this because of the large grant available. Interested to know how other people get on.

Apparently, in Denmark and other forward-thinking countries, 60 percent of new builds have ASHPs.

Might you want to consider installing under floor heating? Obviously involves pulling up the floors but it works very well with ASHP and saves even more room with no radiators. Just worth a mention if you're looking at options. Also do you have room for a big water cylinder, ideally as close as possible to the heat pump (but inside the house). Have you got a good spot to locate the heat pump outside, not too close to neighbours?

My new air source heat pump is virtually silent. It's about five feet tall and installed close to my kitchen, but closer to my "office", and not a million miles from my open bedroom window, and I've never heard it.

I'm having one installed in a few weeks, I've solar, the immersion thingy, a plug in hybrid car and 20KW batteries - I'm hoping to charge the batteries at night with low cost electric then a combination of solar and battery to run the ASHP during the day

We bought a new build house with an ASHP and under floor heating and we have been absolutely floored by the cost of running it (long before the cost of energy rocketed).

Its also a nightmare finding anyone to come and service it or repair it when it goes wrong.

Our water tank doesn't hold enough water for more than 3 people to have quick showers in the morning. If we increase the temp of the water in the tank, the ASHP can't get there so it switches to immersion heating to increase the temp which makes it all even more expensive.

I miss my combi boiler and its endless supply of hot water.

You should expect anyone who quotes for a heat pump to do a full heat loss calculation to get the size of the heat pump right. With heat pumps going too big will make it run very inefficiently. There are people out there just whacking in oversized heat pumps and running away.

EVM (electric vehicle man) has some stuff on YouTube about getting his heat pump installed which is useful. Heat Geek is a wealth of information (also YouTube. They are a firm who do accreditation of installers and some of their stuff is aimed at professional installers whereas some is for the general public)

Anything you do towards getting heat pump ready (insulation, larger radiators etc) will also make your existing gas heating run more efficiently so it's not wasted effort to get ready for a heat pump even if you're not ready to get it installed yet.

I’ve got a heat pump , installed 3 years ago, and it’s fine but I only installed it when the oil burner was on its last legs, and was getting unreliable. It’s not noisy. My son needed a new boiler last year, but he has gas in his village, so went with a new gas boiler.
I would leave it until you need it. To be honest the guy who gave you a quote should have said that.