OT Heat Pumps and Solar

[Mariner]

A bit off topic but more liable to get a sensible discussion here.
Anyone replaced gas with Air Source Heatpump, Solar Panels and Battery Storage?
If so how is it working out?

[whitestone]

My brother has 40 solar panels on a south facing barn- about 60m2 in total. At current tariffs they generate about £1300/year obviously dependant on how sunny it is. His setup feeds into the grid if he isn’t using it all.

He looked into heat pumps but was told that they didn’t work so well in old stone built buildings so didn’t fit one.

[lune ranger]

We have 36m2 of solar PV, a solar thermal system for hot water and a ground source heat pump.
In order to get the best from the system we had a considerable retrofit to our house - underfloor heating, whole house ventilation and almost Pasivhause levels of air tightness and insulation.
The whole thing was a huge investment and disruption but the result is an energy bill - including ‘fuel’ for an electric car - that averages out at £400 a year over the last 6 years for our family of 4, three of whom are at home 7 days a week.

[Bearbonesnorm]

He looked into heat pumps but was told that they didn’t work so well in old stone built buildings so didn’t fit one.

That was my understanding too Bob. A modern build with high efficiency insulation = good. A rubble filled stone house build directly onto the ground with open eves = not so much.

[mikejd]

Not replacing existing gas, but renovation of an old stone built croft cottage. Installed ground source heat pump system. It only really works in this context if completely renovating including insulation to current standards and using an underfloor heating system. This is working well, house is usually warm with hot water. Not cheap, either to install or run, but in our rural location the alternatives were oil or LPG.

Later extension has air source heat pump. This is a timber frame structure fully insulated and underfloor heating. Again is working well.

Solar panels - 16 panels producing, I think, up to 4kW on the barn across the road to the house. Not ideal orientation and Scottish climate means output can be limited, but it does help to reduce electricity drawn and a small income against bills.

[lune ranger]

If you go for it do your research. Aim for a company that can fit an integrated system or you risk different parts of the system not playing together.
It’s less of a problem theses days due to much reduced feed-in tariffs but there are a lot of cowboys involved in renewables.

[lune ranger]

He looked into heat pumps but was told that they didn’t work so well in old stone built buildings so didn’t fit one.

That was my understanding too Bob. A modern build with high efficiency insulation = good. A rubble filled stone house build directly onto the ground with open eves = not so much.

True. But in these circumstances any heating system will have problems and you are forced to deal with reduced thermal efficiency with increased thermal input.
Our main house is mid Victorian stone built.

[hoppy58]

If you have solar pv with a feed-in tariff, it’s well worth having an i-boost fitted for domestic hot water supply. When your pv is generating electricity it sends a signal which automatically sets off the immersion heater, powered direct off the pv and you still get your pv payment...so effectively you get free hot water. We added this a couple of months ago and it works brilliantly. The advantage over solar thermal is that it also works throughout the winter. Cost about £300 plus sparky’s labour - about an hour’s work. Obviously you need a hot water cylinder so doesn’t work for combi-boiler set ups.

Would reiterate that you need to sort out insulation first-once that’s done you should be able to get the benefits of heat pumps. If you’re already living in the house this is more difficult because of the massive disruption caused by retro fitting insulation, particularly for applying internal wall insulation.

We were lucky to be able to start with a building shell and insulated thoroughly, to the degree that we didn’t fit central heating..relying upon internal building heat eg cooker, people etc, solar gain and good heat retention. We have a central wood stove which we light if it gets cold. Also try to draught seal and look at MVHR to maintain good ventilation/ prevent condensation.

Hot water is from the aforementioned I-boost, solar pv and from a back boiler on the stove.

From my experience I would say that, if you can, just concentrate on getting the insulation level as high as possible as a priority, then decide which way to go with heat sources.

[Lazarus]

But in these circumstances any heating system will have problems

Gas would still work but it would require more energy
Realistically , as noted, you require an incredibly well insulated house as they cannot heat as highly as usual central heating. This is the real pro lem with their uptake given how many of us live in cavity walled , chimney in each room houses that were built to be drafty . I am not sure hermetically sealing them is a good idea YMMV
I have lived off grid but that is a different issue.

[fatbikephil]

We have 36m2 of solar PV, a solar thermal system for hot water and a ground source heat pump.
In order to get the best from the system we had a considerable retrofit to our house - underfloor heating, whole house ventilation and almost Pasivhause levels of air tightness and insulation.
The whole thing was a huge investment and disruption but the result is an energy bill - including ‘fuel’ for an electric car - that averages out at £400 a year over the last 6 years for our family of 4, three of whom are at home 7 days a week.

Pretty much what I've heard is required. I 'spose you can do the insulation bit first then the underfloor heating, then the heating system if you don't want to spring for the whole lot at once. That said I've heard that air source heat pumps are pretty ineffective in cold climates (i.e up north) so I suspect I'll hang onto my gas boiler for as long as possible...

[boxelder]

We added an ASHP and PV solar to a '50's, drafty semi and it worked fine. Better payments and up front grants at the time helped. We added a couple of big surface area rads, and later, an extension/play room with under floor. The old lady there now only uses a few rooms and was on zero bills overall, before the latest price rises. We had a wood burner in the open plan downstairs too I guess.
New build has ASHP and smaller panels and is really nice/comfortable, but the panels earn very little and elec bills around £4k/annum. No oil or gas. Three teenagers and a 'nesh wifey' though, so could half that bill I'm sure.

[whitestone]

From my experience I would say that, if you can, just concentrate on getting the insulation level as high as possible as a priority, then decide which way to go with heat sources.

Someone I've been doing work for did up an old house (well it mostly fell down and he rebuilt it) and his comment was "Insulate the f*** out of it!" Their house is totally off-grid: private water supply; septic tank; diesel generator for electric; bottled gas(!) for heat. I queried the latter and he said that they only use one bottle per month to six weeks, the cost wasn't really a problem. Obviously if they'd a normal gas or oil tank the cost would be lower but their current usage is so low that it's not worth installing.

[Mariner]

Thanks for the replies.

lune ranger who did your installation? I am just down the road from you well Devon anyway.

Had the garden landscaped a few years ago so not going to dig it up so limited to ASHP.

I had all the rads over specced when we replumbed the house. Does a boilerless system run as hot or just continuously at lower temp?
I did look at a PV Solar system again over specced with battery storage and hot water accumulator but hey energy crisis phhh.
My 1970s detached house is starting to approach the cost of the draughty old G2* house we had with no double glazing oil heating and woodburners.

[JimH]

Mariner, I’m in Exeter and currently in process of requesting quotes for PV/battery. Did you find the energy crises has put prices of systems up?

[Mariner]

It was several years ago so prices will be somewhat changed since then.
I think it was £14k for over speccd PV ASHP and Tesla battery plus installation.
Scaffolding was extra but last time I had the house scaffolded 2016 it was £1500.

Let me know how you get on.

[lune ranger]

Hi Mariner. I can’t help you really because the architect that designed our system and managed the installation has moved back to Germany post- Brexit.
I could try to look up the names of the contractors if you thought that’s be helpful. I seem to remember Sungift did the solar PV/thermal.

[Wotsits]

I touch on ASHP via work fairly regular (but am not an expert), there's basically two parts- heating & hot water. The best piece of advise for heating is below-

Would reiterate that you need to sort out insulation first-once that’s done you should be able to get the benefits of heat pumps.

From my experience I would say that, if you can, just concentrate on getting the insulation level as high as possible as a priority, then decide which way to go with heat sources.

A well insulated home will be cheaper to heat whatever the system.

With heating the lower the water temp the more efficiant they are, thats why something like underfloor heating works really well, & emitters (convection radiators) are larger to give adequate output. Smaller radiators can also have fans to compensate.
This is why insulation is so important, even more so when the ambient temp drops below 7c, as that's when an ASHP efficiency can start to drop off due to the way they work.

For hot water there'll need to be a storage tank sized correctly for usage (hundreds of litres). Due to the lower water temp compared to a gas boiler they also need a 'anti-legionella' cycle every couple of weeks that raises the water temp in order to kill any bugs. This is often carried out using electric emmersion heaters. As a packaged unit with all the pumps & pipework, they can be quite a size.

Design, installation & set-up are also really important, a well designed system installed & set-up correctly will have sensors throughout & will 'learn' how long things take to warm up, adapting the way it works. There are hybrid heat pump/gas systems where you input the cost of gas & electric & it'll work out the most efficient/cheapest way to heat given the current temp reading.

High temperature heat pumps are also availabe that are marketed towards retro-fits where existing radiators prefer to be kept, these tend to be cascade systems where there's multiple stages of heating.