Solar panel advice

Ingsy · 19 July 2018 at 2:19PM

Hello, I am after some advice regarding getting solar panels. I have had three quotes, one from Project Solar (who I can tell from reading a couple of threads on here are not exactly favourites!) by someone who came out to my house. One from Solar Century (who are linked with IKEA?) who have done it from Google Maps views of my house, and will charge £125 to come out and survey.

I also did a quick quote with E-On also.

With all these numbers, bear in mind I have a 600W PC running 24/7 so my usage is approx 8500 KwHr / year. and my electricity bill is forecast to be £1100 for the next 12 months - this is main reason I'm looking into solar!

Project Solar:
14x Evolution Max Life Solar Panels (4-off TIGO controlled due to a chimney casting a shadow)
1x Solax invertor
1x Hot Water controller
1x Volt Doctor unit (my mains voltage is at 238V and reducing it to 220 can apparently give me savings?)
1 x Boiler Doctor (not quite sure exactly what this does?!)

All installation, 48 hr repair etc etc. Grand total £10,883

He used 16p/kwhr (which apparently is standard? I have just switched to Scottish Power and have a fixed 12.1p for the next 12 months) and said that the payback would be £1060 a year including FIT, savings on gas from heating hot water, savings from the volt doctor unit etc (this payback is apparently guaranteed and they will pay the difference if it's less).

Solar Century:

13x Q-Cells 295W Mono
Solax invertor
All installation etc. Grand total £6412

They also used 16p/kwhr in their calculations and suggested the payback would be £311 per year based on FIT and electricity savings as the system is predicted to produce 2,949 kWhr per year.

E-ON:

Doesn't say how many panels on their quick quote, but predicted a production of 3,287 Kwhr / year and a cost of £4895. With a payback of £487 per year.

My roof faces approx 25 degrees east of south (if that makes sense!) and my roof is at a pitch of approx 35 degrees.

Obviously there is massive differences in cost, and predictions. Can anyone give any advice as to which might be closest to correct? Two seem to give a payback of about 10 years, with Solar Century being about 20! Is this fairly standard?

Can anyone recommend and other solar companies I could get in touch with for a quote? I am based in mid-essex if that makes a difference.

Any replies / comments / feedback is much appreciated.

forgotmyname · 19 July 2018 at 3:37PM

Your 600W PC, is that the power supply?

Unless its a very very high spec and its running maxxed out 24/7 it wont be using 600watts.

I have a 600W PSU, but as im typing this my PC is running at 87watts. Ryzen 1700, 16GB with SSD's and HDD's.

Ingsy · 19 July 2018 at 3:52PM

It's a 750W PSU running at 590-600W. I'm mining.

Ingsy · 19 July 2018 at 3:55PM

I've found a PVGIS calculator, found my house on it and got these figures:

PVGIS estimates of solar electricity generation

Location: 51°52'28" North, 0°32'22" East, Elevation: 57 m a.s.l.,

Solar radiation database used: PVGIS-CMSAF

Nominal power of the PV system: 4.0 kW (crystalline silicon)
Estimated losses due to temperature and low irradiance: 7.4% (using local ambient temperature)
Estimated loss due to angular reflectance effects: 3.1%
Other losses (cables, inverter etc.): 14.0%
Combined PV system losses: 22.8%

Fixed system: inclination=35°, orientation=-25°
Month Ed Em Hd Hm
Jan 4.21 131 1.27 39.5
Feb 6.74 189 2.07 57.9
Mar 11.00 342 3.47 107
Apr 15.10 453 4.88 146
May 15.70 487 5.16 160
Jun 16.00 481 5.36 161
Jul 15.70 488 5.30 164
Aug 13.90 430 4.63 143
Sep 12.20 366 3.99 120
Oct 8.44 262 2.69 83.5
Nov 5.54 166 1.71 51.3
Dec 3.69 114 1.12 34.7

Yearly average 10.7 326 3.48 106

Total for year 3910 1270

Ed: Average daily electricity production from the given system (kWh)
Em: Average monthly electricity production from the given system (kWh)
Hd: Average daily sum of global irradiation per square meter received by the modules of the given system (kWh/m2)
Hm: Average sum of global irradiation per square meter received by the modules of the given system (kWh/m2)

So this suggest a generation of 3910 KwHr per year. Higher than all of the quotes.

Does this really need to be this confusing? :-)

jimjames · 19 July 2018 at 7:59PM

If that location is Essex then ours in Kent shouldn't be too different. We are in Kent with 3kWp panels, perfect direction and no shade, on average we're getting just over 3000kWh from them each year so with 4kWp you should get over 4000kWh if you have no shading.

http://solar-panels-review.321web.co.uk/index.php/yearly-comparison-of-solar-pv

I'd also be very wary of any company offering that sort of guarantee for payment. Effectively you'll be paying it via the higher price and if they go bust then the guarantee is likely to disappear too

Ectophile · 19 July 2018 at 10:14PM

If your mains is currently running at 238V, then fitting a voltage optimiser will save you little or nothing. People have been pushing them for years as "energy saving" devices, but they make no difference with most appliances these days.

The only reason I can see for fitting one is if your mains voltage ever goes above 253V, causing the inverter to cut out.

Ingsy · 20 July 2018 at 10:36AM

Thanks very much for the replies.

Jimjames - that link is very interesting. Thanks.

Zarch · 20 July 2018 at 11:59AM

From one of the quotes:
1x Hot Water controller

Do you have water tank? As these devices only work with water tanks. They are of no use if you have a combi-boiler.

iBoost is one of the most popular devices:

https://www.marlec.co.uk/product/solar-iboost/?v=79cba1185463

Easy way to calculate your own FIT payments.

Current Generation tariff is 4p per kWh and current Export tariff is 5p

You get paid the generation tariff for all that your system generates and you also get 50% of that in export payments.

So a 4kWh system would be 4000 x 0.04p for the generation = £160 and half your generation for export (2000) x 0.05p = £100. Total FIT per year £260..... this will then hopefully rise each year with inflation.

Any other money made would be from savings off your electricity bill, which as you say is currently 12.1p per kWh. If you could save £20/month, so £240 year..... that would make £260 + £240 = £500/year.

Hope that makes sense?

Not sure where that guy is saving you a grand a year?

And yes, 8,9 or 10 years is a sensible break even ball park for a solar install under the current FIT payments. Obviously as long as the install cost is reasonable and you're not getting conned, ie £10k.

Solar panel advice

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