Air source heat pumps/ Solar systems

Any real life experience with ASHP and solar systems?
We currently have a old oil system.
I understand they are expensive to install but my logic at looking at them is a belief that oil costs are only going to go up.
Thanks in advance

The context for this makes quite a bit of difference so if you’re able to explain a little bit about your house – location, construction, orientation etc. it will help give some advice/relevant replies.

🙂

Generally speaking the two are not mutually compatible.

Typically with a solar system, you get around 5 times the production in June as you do in January. You will barely have any energy left over for heating over the winter.

Air-to-air heat pumps are a bit better (i.e. air con unit with heat pump mode). As the air con works well with the solar production in the summer. Also, if you get a split unit (not portable), the efficiency tends to be higher than anair-to-water system in heat pump mode, as you only need to heat the air to 20 odd degrees as opposed to 40+ degrees when heating water. And it is easier to use as a supplementary heat source to e.g. oil as you can keep the existing radiators etc.

You need to look at insulation and air-tightness first as ASHPs cost more to run – I get £600/year RHI payment to compensate in a very well insulated house. Installation costs were £10k on a new build. There’s supposed to be a new grant scheme soon as RHI closes for new applicants next month.

My parents fitted ashp to their 6bed bnb which is 1950s built

It’s fed by a 7kwh solar array (50% of which is sun tracking )

It works well * how ever it’s sodding slow to heat hot water. They ended up with two x 250 l tanks as the turn around on a tank was more than 12hrs.

* it’s in France.

Based on my solar tracking since august last year the solar will make very little dent in your ashp usage in uk cold periods.

I rented a place a few years ago which had a GSHP and a wind turbine.
There was a bathroom in one of the barns which it did the heating and hot water for and it was fine for that but that’s really all it could cope with.
This was 2015 though and it was a coue of years old then, things might have moved on.
.
Basically for a heat pump to work you are going to need a lot of panels/turbines!

So the property is approx 130m2, 1980,s bungalow up near Inverness. It has suspended floors which need insulating but everything else is good regards insulation and double glazing.
House is SSW facing.
Initially we were planning to get a solar set up to do the general elec and install a new unvented tank with Emersion heaters that could run off the OF boiler and Solar panels.
It’s only now that the oil tank needs replacing that were thinking it would be a good time to upgrade the whole system instead of sinking cash into a new tank set up.
Hmmm

With a ASHP you’ll need larger rads as the temperature is lower.
We generally put underfloor heating in for ASHP – can be done with suspended floors but you need the trays & insulation.
It will generally act as a boiler does which prioritises heating over hot water.
Solar thermal is good for the hot water.

I’m in the process of buying a bungalow with ASHP and solar water/photovoltaic panels, so ask me in 6 months what I think 🙂

I have both an ASHP and solar PV on my house in Central Belt of Scotland.
As stated above the two systems do not interact greatly and should be considered separately.

This winter our 4kw solar array has exported between 40 and 120 kw per month. Most of the export will be during the middle of the day and is highly variable.

ASHP will normally require larger radiators and possibly large bore water pipes, however in an 80s property pipes will probably be OK.

I am happy with both ASHP and solar PV, ASHP has significantly reduce kwh used and CO2 generated even more, it will probably not save ££ unless the balance of electricity and gas prices change.

@rents I’m happy to discuss ASHP and PV further if it would help.

“I’m in the process of buying a bungalow with ASHP and solar water/photovoltaic panels, so ask me in 6 months what I think 🙂”

So ask me in 12 months as 6 months will have all the positives of summer without the lower effects of the winter months

So ask me in 12 months as 6 months will have all the positives of summer without the lower effects of the winter months

True. Or if the conveyancing process doesn’t speed up a bit ask me in about a decade!!

This winter our 4kw solar array has exported between 40 and 120 kw per month. Most of the export will be during the middle of the day and is highly variable.

Which direction does that face .

Those are low exceedingly low numbers.

Not for winter they aren’t, I’d say that’s about spot on.

4.2kwh system south facing in cheshire.

November, December and January are the lowest months, this December just gone has been my worst ever at 51KWh for the month, best of 119Kwh this January.

Hi Trail Rat,
The kwh values I quoted are export, after all home use, not generation. The ASHP will run for some of the day in winter and we wash clothes, dishes and charge the car when the sun shines.

My PV system is 4kw and produces >25kwh per day in summer so broadly what I would expect.

Really? so you have more than one meter installed? If the figures are for export only not including generation then that’s a very high generation for winter for only a 4Kw install.

I stayed at a friends house this week. Its brand new and done by an architect for them. Its a big bugger (especially the kitchen/lounge/diner) with underfloor heating, solar and air source and its driving him and his wife potty.

The big bedroom over the double garage is the coldest.

Current costs are around £450 pm but his wife still finds it a bit colder than ideal. I was fine in a hoody but it wasn’t tea shirt temp. Hopefully this balance out in his favour over the whole year.

The costs are offset for the next 7 years because they chose air source and he is chasing draughts at the moment which will hopefully see further improvements.

He also ran a flue for a log burner during the build so has that option too.

so you have more than one meter installed?

That’s normal. I have 2

His numbers make sense now he says they are export only.

Still evolving technology

Still evolving technology

Indeed. A bit like, for instance, gas boilers.

I first came across an installed air source heat pump in the mid 1980’s (at a high school in what is now Moray). Not saying is was working brilliantly, but HP’s are not new. I was an apprentice at the time, it all sounded like mumbo jumbo cultishness to me at the time 🤪

Also that second video, hate to break it to you but condensing boilers also have a condensate pipe that can freeze… make sure you route it internally rather than external… I could tell you horror stories about gas and oil boilers (probably starting with CO, ¡the silent killer!, if I really want to up the hyperbole or how the gas leaks can kill you too… i’ve had people refuse gas heating upgrades they don’t want gas in the home).

Condensing boilers need to operate at 60F 40R (which would make conversion to HP a lot easier) but oh no, turns out nobody does that so your boiler isn’t as efficient as the manufacturer/designer/fitter makes out… see, it’s like shooting fish in a barrel. Cowboy plumbers are the same whatever.

Oh, don’t install battery/power wall with PV and ASHP as for 3-6 months a years all the PV is going to the HP and your battery depletes… and stops working.

Tbh the best advice is to build houses that don’t need much heat in the first place (cf Passivhaus).

Sorry to hijack this thread..

New house I’ve bought (hopefully…) has oil-fired central heating and hot water. First thing I’m going to do when I move in is get solar PV on the roof. Hopefully that’ll offset some of the water heating cost over the summer via a couple of immersion heaters in the hot water tank, while letting me stick a couple of kWh into the car each day.

It’s already EPC B so at least any heat that goes in should mostly stay inside. Will keep the oil for most of the heating (there’s an electric fire in the lounge with a flue fitted for gas if required) but will probably add an AC unit for the summer. Can they all work in reverse to suck heat from outside and dump it into the house?

£450 pm but his wife still finds it a bit colder than ideal

How big is it? Based on the bills for my 110m2 house, you’d need to be looking at 330m2 which is nearly 3x the size of the average UK home.

Can they all work in reverse to suck heat from outside and dump it into the house?

Some ASHPs have a cooling function, but then you really need to be looking at blown-air heating/cooling rather than radiators so would require fairly extensive modifications to fit.

Oh, don’t install battery/power wall with PV and ASHP as for 3-6 months a years all the PV is going to the HP and your battery depletes… and stops working.

Not with modern units that’s not how they work.