Solar Panel Basics.....

Martyn1981

Weakestlinks wrote: »

Hi
I live in South East England about 10 miles north of Hastings in a detached bungalow with a South facing roof and no shade. It's not a massive roof (about 3.5m x 8.5m) and about a 40 degree slope.

Thanks

Hiya, and welcome.

Just a quickie to say that if you have a useable space of 3m by 8m (after allowing for around 200 to 300mm all round for various reasons) then you may be able to squeeze in 'regular' 15 panels landscape in 3 rows of 5.

That would be cheaper than going for the higher power units, and still give you 3.75kWp (or more as some panels can be more than 250Wp, upto 275Wp)

Also, for some general info, have you tried the PV FAQ thread?

https://forums.moneysavingexpert.com/discussion/3872445

Weakestlinks wrote: »

There is someone home pretty much all day and over the last few weeks I've been monitoring our power use (using an OWL monitor) and between about 9am until 8pm we use about 12KWh of power

This seems an awful lot, but if correct, then you'd obviously save more on your leccy bill (from PV) than most people, since, the more leccy you consume, the more PV you'd make use of rather than export, or convert to hot water.

Mart.

Ectophile

I believe that new panels may be better in subdued daylight, but don't expect miracles.

Having watched the inverter's display in different weather conditions, my rough rule of thumb is:

Bright direct sunlight = close to 100% of rated output.
Moderately overcast = 10% of rated output.
Heavily overcast = 1% of rated output.
Really horrible weather = not enough power for the inverter to start up at all.

Kernel_Sanders

Ectophile wrote: »

Having watched the inverter's display in different weather conditions, my rough rule of thumb is:

Bright direct sunlight = close to 100% of rated output.
Moderately overcast = 10% of rated output.
Heavily overcast = 1% of rated output.
Really horrible weather = not enough power for the inverter to start up at all.

This is much nearer to what you can expect, although the first one only applies to your peak period of the day and year and assumes minimal haze.

Weakestlinks

Great info - everyone.... thanks very much.
Particularly love the PVoutput chart from theboylard - brilliant!
and great call on the 15 panels landscape idea - I'm pretty comfortable on the right way to go now.... I just need to find a good installer. One quote so far... North of £12k!!!
I guess they don't want the business.

Martyn - when you say "(or more as some panels can be more than 250Wp, upto 275Wp)" do you have an actual model of panel that would do 275Wp that I could get pricing for?

thanks again

Martyn1981

Weakestlinks wrote: »

Martyn - when you say "(or more as some panels can be more than 250Wp, upto 275Wp)" do you have an actual model of panel that would do 275Wp that I could get pricing for?

thanks again

Morning. Here's a link to a shop (I have no association to them), the link is to the YingLi panels, but have a nose at the other models they sell:

http://www.swithenbanks.co.uk/shop.php?c1=Solar%20Photovoltaic%20Equipment&c2=Solar%20Panels&c3=Yingli

Note that 275Wp would actually be a tad over the 4kWp FiT rate, so you'd need to aim for 265Wp.

[Edit: Such as the Hyundai 260Wp or the Canadian Solar 265Wp and so on.]

Have a browse and a thunk.

Mart.

Weakestlinks

Thanks - will do
.... and is Mono better than Poly? I think I read that somewhere....

Weakestlinks

one more thing
Does anyone have an opinion on the projected yearly savings I was offered from a recent solar sales rep....

my yearly electric bill is about £850..... year 1 savings from using solar panels ....£560.....

Is that a reasonable projection or outrageous\borderline mis-selling?

thanks

Martyn1981

Weakestlinks wrote: »

Thanks - will do
.... and is Mono better than Poly? I think I read that somewhere....

Mono is generally considered a bit better, and poly's tend to be slightly cheaper. Also the appearance can be a bit different as the mono's are cut from a single (mono) piece of silicon.

Weakestlinks wrote: »

one more thing
Does anyone have an opinion on the projected yearly savings I was offered from a recent solar sales rep....

my yearly electric bill is about £850..... year 1 savings from using solar panels ....£560.....

Is that a reasonable projection or outrageous\borderline mis-selling?

thanks

As always, it'll depend on your consumption pattern, especially if you use a lot of leccy during the day, if water is leccy heated or not etc etc.

However, initial thought is that that is outrageous, I save about £180 pa, and generally suggest savings in the £100 to £160 range, perhaps £120 and see how it goes. Obviously people can save more, but better to be a bit pessimistic to make sure the investment stacks up. For you, with such a high bill, your savings could be more, but crucially depends on when you currently consume it ... daytime?

Thinking out loud, any chance that £560 was the total income and savings (FiT + export + leccy savings) which it could be for say ~3kWp system?

Mart.

Weakestlinks

Thanks Martyn
The surveyor came round today and it was refreshing to talk to someone who's not a salesman and know what's what. I feel much better informed now both through this forum and in talking with the survey guy.

Thanks for your thought on the leccy saving - I'll run my figures again based on about £150 pa..... we do use a lot of leccy and all during the day. We're not sufficiently disciplined to run things like washing machines and dishwashers overnight - so solar would be useful there.

the £560 was definitely just our leccy saving.... the projected total saving for year 1 that includes leccy saving, FiT, Export and savings on oil by using the solar to heat the water (via immersion).....wait for it......drum roll....£1600 )

Martyn1981

Hiya, glad to hear you'll use £150 to help evaluate the investment, but just to contradict myself, given your high leccy bill, and daytime consumption, you may well save more, but don't want to mislead you.

Checked out 'just above Hastings' on PVGIS (see the PV FAQ for a walkthrough) and it looks like really good generation, nearly 1,100kWh per kWp, which is pretty mighty.

So a 4kWp(ish) system could generate around 4,000kWh+ per year. Being extremely optimistic, if you could use 50% of that (which most Pv'ers will tell you is very hard), then potential savings of 2,000 * 15p (or so) = £300. So you can see why £560 is nonsense.

Moving on to that £1600, even allowing for the £560, that still leaves £1,040. Let's be very optimistic and assume 4,400kWh of generation, then that's worth 14.38p FiT + 2.385p export (50% deemed exported @ 4.77p) = 16.765p.

4,400*16.765p = £737.66

I can't imagine the water heating element of your oil bill is £300, is it? Let alone the amount that you can avoid through leccy diversion.

However you analyse it, those numbers are seriously dodgy, and were probably designed to hide the high price, by making you concentrate on the inflated income/savings.

Right, end of the negatives. You have a good location, great generation, high daytime leccy consumption, and expensive oil hot water. So PV will definitely work well, just need to get a good price.

Mart.