PV’s Essential for ASHP/UFH?

[soapstar]

Hey Folks,

 

Getting quite close to finally pulling the trigger on this build and of course there the many questions popping up in my head every day, especially after browsing this forum each day!

 

The latest niggle in my head is should we have planned to have solar panels along with our ASHP?! Our 290m2 house will have UFH on the ground floor with rads upstairs. Plumber has quoted a 16kw ASHP with a 300 tank (50 litre buffer tank).

 

Bit of a basic question however what would the PV’s (if we had them) be best utilised for exactly? To simply power the heat pump? Given the plumber has quoted a 16kw pump is it asking a lot for PV’s to power such a pump and therefore  would it be cost effective? 

I have also heard people using solar panels for the hot water only?

 

Whatever the outcome we 100% do not want masses of PV’s on the roof, a couple would be acceptable on the integral garage I think.

 

I will admit I am a little clueless with solar panels and their associated cost to install - any figures would be greatly appreciated.

 

thanks again for your help guys

[ragg987]

Are PV essential, no. Will

they contribute energy, yes, but since the Fit tariff stopped the economics are not great.

 

Each panel can only generate between 250Wp and 350ish. So no point with 2 panels, the cost of the inverter means it cannot make any economic sense.

 

Bear in mind that solar generation is at a peak when you do not need space heating, so there is an imbalance here. You need to be able to consume the power in the warmer months.

 

This can be e.g. solar diverter, either to DHW or to a battery (e.g. powerwall or even your electric car), though of course you may be able to consume some of the power by timing washers and other consumers. And yes the ASHP can benefit, but best in mind the winter peak.

 

A 4kWp solar install can cost roughly £5k, some here have managed cheaper by buying cheap and fitting themselves.

 

A solar diverter is about £100 plus fitting.

 

A fixed battery I am not sure, but seen figures mentioned of £8k +.

[Ferdinand]

I was quoted 4K for a black on black 4kWp install 3-4 years ago as a best price for a straightforward install on a bungalow, and 4.5k for something which was more branded.

 

I think now you should be some way below 5k, unless the squeeze in the trade has driven prices up again.

 

Get some quotes.

 

F

[soapstar]

52 minutes ago, ragg987 said:

Are PV essential, no. Will

they contribute energy, yes, but since the Fit tariff stopped the economics are not great.

 

Each panel can only generate between 250Wp and 350ish. So no point with 2 panels, the cost of the inverter means it cannot make any economic sense.

 

Bear in mind that solar generation is at a peak when you do not need space heating, so there is an imbalance here. You need to be able to consume the power in the warmer months.

 

This can be e.g. solar diverter, either to DHW or to a battery (e.g. powerwall or even your electric car), though of course you may be able to consume some of the power by timing washers and other consumers. And yes the ASHP can benefit, but best in mind the winter peak.

 

A 4kWp solar install can cost roughly £5k, some here have managed cheaper by buying cheap and fitting themselves.

 

A solar diverter is about £100 plus fitting.

 

A fixed battery I am not sure, but seen figures mentioned of £8k +.

 

Interesting thanks. I never thought of the fact that solar power is at its greatest in the summer months when you do not need space heating. Given the price to store this via a battery would be 8k plus would be taking us out of our budget.

 

So I can only conclude my assumption that we could use solar panels to power the ASHP  (or a large part of the energy requirements) seems impractical without a great number of panels? From what I have been reading a standard home requires around 20m2 of panels to produce around 3000kw, therefore with our 16kw heat pump this wouldnt be enough?

 

 

[Jeremy Harris]

As a guide, this is a plot of the generation from a 6.25 kWp system, facing a bit west of south and angled at 45° at our location:

 

 

It illustrates pretty well how PV generation drops a great deal around October and doesn't pick up again until March, making it less than useful for heating.

 

[ProDave]

Solar PV has to be cheap to justify itself now.  I spent £1500 self installing a 4kWp ground mounted system, financed by expected self usage of £250 worth of electricity per year giving a 6 year payback time.  Much more than that, and I would not have bothered.  I think you would have to be "dedicated to the cause" to pay more than that for a professionally installed system.

 

At 4kWp batteries are not essential.  Simply by using the big appliances in the daytime (washing machine, dishwasher, tumble dryer) and diverting surplus PV to the immersion heater for additional water heating, I have kept export down to a minimum.  I would like some battery storage but that would have to be cheap, so not yet.

 

Battery storage would become more important if you fit more than 4kWp as it then becomes harder to self use all you generate.

[Jilly]

Pro Dave, what company did you buy your PV's from?

 

[ProDave]

47 minutes ago, Jilly said:

Pro Dave, what company did you buy your PV's from?

 

I got mine from Bimble Solar. The only way I got them as cheap as I did was they were second hand, claiming to be from a solar farm that was upgrading, and about 4 years old.  We did well, because they were described as having a "degraded back sheet" but only 2 out of the 25 panel lot had any damage and it was extremely minor.

 

 

This is what Bimble have at the moment https://www.bimblesolar.com/solar/individual

 

e.g. 275w panels for £75 plus VAT,  so 14 of those would give you 3850W for £1260   I got mine for slightly less than their list price as they also sell on ebay.  I paid £255 for a new 4kW inverter.  The rest was mounting hardware etc.

[Jilly]

Fab thank you