Anyone here got solar? Just had a quote for a 7.5kW system with a 9.5kWh battery and a Givenergy 5kW hybrid inverter. G99 approval etc.
We’ve been quoted £14,900. Is this out of order or not unreasonable?
Tim
Regardless of the quote, what are the economics of having this system?
Estimated payback time of 7 years. Estimated savings of £52,000 over its lifespan.
Tim
I was quoted for a 10kW system with an estimated payback time of 20 years. I did not follow it up.
Most of what you generate will be during the summer when you possibly need it lest but to make the most of the savings you need to use all of what you produce rather than feed it back to the grid.
In winter you may not be able to generate enough to, say, charge an EV and the battery. If you are also going to have electric central heating as well then you will be buying from the grid during the winter.
You really need to ignore any figures on savings given by a salesman and do some sensible calculations yourself.
Solar panel 'efficiency' (capacity factor) is about 5% of the nameplate capacity in winter (short days, lots of cloud etc), rising to about 25% in summer, and averaging somewhere around 10-15% across the year. Much depends on type of panel, their orientation and their latitude - the further north the worse they get. South of France and North Africa are probably OK, but in northern Europe it's questionable whether they ever generate enough electricity to cover the energy required to make them (EROEI: energy returned on energy invested), but it's a difficult calculation.
Some real numbers here from a solar farm in the south of England. Browse around it.
I think we'd need to see how that figure was arrived at.
So are you saying that in winter the OP can expect to get a massive 375W and in summer 1.875kW ? Would that be average over some period, or peak at 12.00 midday on some average day?
Peaks.
I agree it needs case-specific calculations and the savings look high at first sight. (>20,000+ kWh p.a. on the back of my envelope.) OTOH Tim+ is an EV user so might make good use of the battery and soak up even the summer output.
Let's price up the hardware:
400w panel, £126:Scaffolding hire/putup/takedown £1k (cheaper if they have their own)
I CBA to price up all the rails and screws and stuff (which will depend on the roof anyway), but let's say same cost as the panels: £1134
Isolators, wiring, switchgear etc, £300
No VAT applies
So our crumpled manilla comes out with hardware cost of:
1134+5947.20+1000+1134+300 = £9515.20That leaves £5k for the labour, project risk, etc.
Labour will depend a lot on the install location. Likely two people needed, assuming they will do both the roof install and the electrics (although they could sub out the mains side of things).
If it took two people a week that would break down to £62.50 an hour. Which is not an off the map rate for electricians, especially in a pricey part of the country.
Theo
We had a 4.4kW solar panel and 13kWh battery installed end of July 2022. The hybrid inverter and batteries are Growatt. Our inverter is only 3kW which can be a bit limiting at times but we can live with it.
Our installation cost £12,500.
Alan
Those %ages have to be averages over several weeks or a month or three, otherwise it wouldn't be effected nearly so much by the reduced hours of daylight in the winter months. Whether an average of 375W is 'massive' compared to a maximum output of 7,500W, is subjective, but it might come as a bit of a shock if someone is assuming they'd get
7,500W 24/7 in winter and do their costings on that basis."Solar PV panels have a capacity factor of around 10% in the UK climate. In October 2022, home rooftop solar panels were estimated to pay back their cost in ten to twenty years" from
ISTR that Harry used to get about 15% from his panels, and I had quite a correspondence with him to get the right figures from him. He tended to over-estimate his yields. Can't find it now.
Another site the OP might find useful, posted by a private individual about their own system
There are some calculations on my solar garage example wiki page:
(this is not a system I've built to confirm the projections)
Theo
Many thanks to Theo and everyone else who actually tried to answer my question rather than questioning the plan.
Of course I should be DIYing it but it’s a tad beyond my capabilities. ;-)
Tim
and if you DIY it, you don't get the MCS paperwork and therefore cannot get the solar feed in tarriff or whatever its now called!
Battery and inverter are around £5k, panels are £200 or less each, what, say 20, thats £4000 tops, ancillaries, like cables, isolators, CUs, clamp meters etc wont be over £1k. £5k ish sounds a lot for installation.
That's why you have nearly 10kwh of battery storage, no need to export anything then. And, on the few occasions when you will be close to export, you turn on the hot water, or put the washing machine on.
Good post Theo
In March my daughter had a similar installation with SE and SW facing strings totaling 6kW installed power, 5kW hybrid inverter and 10.5kWh (90% usable) LiPo battery, total cost £12k including a Zappi EV charger. She still uses a combi for DHW. Budgetary constraints mean heat pumps will have to wait.
Of the 2931kWh produced to date 1476kWh self use at £0.39 and 1454kWh SEG at £0.15. She has bought in 103kWh in the period. This has covered all her household use and EV charging. You could debate the £0.39/kWh for the car charging as it could have been done offpeak, she hasn't investigated those tariffs yet and won't till autumn.
As the money was sitting in an ISA at 1.4% the £794 income looks decent and I never had the inclination to play with stocks and shares.
I wasn't there to watch the installation, scaffold erected 4 days before roofer who worked on his own by fixing the framework then stacking the
13 panels upright at the bottom of the scaffold and hooking them with a bit of rope, all completed in a day. Electrician turned up 4 days later at midday and completed it by 11:00 next day.
My system is a smaller 3.64 kWp, and has been in operation since
2010. The FIT has long since paid for the system. The average monthly kWh over that period is as below.Jan 108 Feb 179 Mar 295 Apr 419 May 490 Jun 475 Jul 469 Aug 435 Sep 334 Oct 213 Nov 118 Dec 91
Total 3528
Chris
I think in this country this is a bit like overkill. I mean if I lived in a sunny place I'd go for it, but a friend tells me that their hot water heating panels were cheaper, no batteries and the heating takes place on even cloudy days. If you could get more efficient solar panels, then maybe, but how long till the pay back and how long would these cells, battery and electronic last before needing to be replaced? Brian
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