solar panel confusion

dreaming

Have started a thread elsewhere but was directed to this board.

Have 3 companies quoting this week for solar panels so thought I would read up on pros/cons etc. here but am feeling more confused. Can someone explain in simple terms please.

Background - looking to reduce elec. bills when I retire later this year. Live alone in 2 bed bungalow with southeast roof. Consider myself a light user (but could be better I guess). 1st quote is in for 10 panels estimating 1908 kWh/year - just under 4grand.

Have been reading about changing elec. usage (putting w/m & d/w on in day etc.) but don't quite understand the export/import that I've been reading about. Is it that I should try to use the elec. the panels generate in the day as much as poss. and export to grid (does this mean "selling" it back?). Then the cost of what I use at night/in winter etc. (importing) should be balanced out (hopefully) by the sale of the export + FITS? So although I will still have a elec. bill it will be somewhat reduced (at least in summer) but offset by FITS + export?

Sorry if this is a dumb question but reading some of the stuff on here has made me more confused than I thought I was this morning. The guy who quoted seemd ok but I need to be able to weigh up what he has said.

Cardew

You get the subsidy(FIT - Feed In Tariff) for all the electricity you generate - regardless of where is it goes - exported or used in your house.

It is also assumed that you will export 50% of the energy you generate and you get a further payment for that 50% regardless of exporting 5% or 95%.

So if you did generate the 1908kWh that is predicted, you would get the present rate of FIT on the whole 1908kWh and you will get a further payment for 954kWh deemed to be exported.

WestonDave

Export means energy you don't use and which goes out to be used by others on the grid. As far as finances are concerned export is somewhat irrelevant as the system assumes you export 50% of what you generate (because to work out what you actually export would require another meter and more costs etc). So on that basis you can effectively add half the export payment rate to your FIT rate and just assume you get that for everything you generate.

What that means in practice is that because export is an assumed figure rather than measured, the more you can use the more benefit you get - so if you can run your dishwasher during the day rather than at night then you do it for free off the panels with no impact on what you get in. Some go even further by having systems to "dump" spare generation to heaters or immersion heaters but that needs to be approached with care so that the set up costs don't outweigh the savings.

rogerblack

dreaming wrote: »

1st quote is in for 10 panels estimating 1908 kWh/year - just under 4grand.

This is presumably a 2.5kW system, the numbers about are reasonable for 10 panels and that output. (Assuming the roof is unshaded!)
Of this, if it's installed now, and your property gets a D rated EPC, you will get about 15p*2000 feed in tarrif payments - £300.
You will get about 4.5p/kWh for half of the above as the amount you're assumed to have exported - so about another £50.
You may save an additional £50 or so in electricity, this will strongly depend on your usage patterns.
So, around £400 return a year.
If you have to borrow the money, this will greatly affect your returns.
In addition, at some point you may need to replace the inverter, which is likely to be around £500 by that time.

Very, very importantly, if your house does not get a D rated EPC, you will get 7p, not 15p/kWh.
This drastically changes the numbers.

If you have room for more panels, and can invest the cash now, it is a good secure return.

On a related topic.
If you will need to claim any means-tested benefits, then there may be complications due to the FIT being treated as income.
If you are investing in solar so as to get below means test limits, you may be treated as still having the capital.

Martyn1981

dreaming wrote: »

Have started a thread elsewhere but was directed to this board.

Have 3 companies quoting this week for solar panels so thought I would read up on pros/cons etc. here but am feeling more confused. Can someone explain in simple terms please.

Background - looking to reduce elec. bills when I retire later this year. Live alone in 2 bed bungalow with southeast roof. Consider myself a light user (but could be better I guess). 1st quote is in for 10 panels estimating 1908 kWh/year - just under 4grand.

Have been reading about changing elec. usage (putting w/m & d/w on in day etc.) but don't quite understand the export/import that I've been reading about. Is it that I should try to use the elec. the panels generate in the day as much as poss. and export to grid (does this mean "selling" it back?). Then the cost of what I use at night/in winter etc. (importing) should be balanced out (hopefully) by the sale of the export + FITS? So although I will still have a elec. bill it will be somewhat reduced (at least in summer) but offset by FITS + export?

Sorry if this is a dumb question but reading some of the stuff on here has made me more confused than I thought I was this morning. The guy who quoted seemd ok but I need to be able to weigh up what he has said.

Hiya Dreaming

As explained, don't worry too much about the export part, it will simply add income of 4.5p at 50% of generation. This part is largely out of your control.

What is important, is to do what you mentioned, and try to shift as much of your consumption to match generation, since there is no storage, 'it's use it or lose it'.

Hopefully this thread will explain some of the basics, post#1 sections 1, 2 & 3:

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

Price wise, do keep chatting on here, and list some of the specifics. As Roger said £4k is ok, but a little cheaper would be nice.

Will that system fill your whole SE roof? There are a lot of fixed costs with PV (scaffolding, admin) and others that will not go up too much with a larger system (labour, inverter, overheads), so always best to go as big as possible if funds allow. You may find that a 4kWp system (approx 15 to 16 panels) will 'only' cost about £6k.

I won't confuse you now with too much info, but if your roof isn't too steep (perhaps 30deg), and you can only fit 10 panels on the SE side, then it might be worth considering using the NW side too. Generation from the NW will be less, but the small (hopefully) additional costs could make it economical.

Let me know if you want some better guesstimates at generation, if the above doesn't sound too wacky. You could also try experimenting using section 5 on the FAQ thread. Happy to help.

Mart.

PS Does your roof(s) get any shading, especially during the better 6 to 8 months? Shading is important. M.

dreaming

Thank you all - that has made the cash side a lot clearer. I can see that it will definitely be worth it if I were to get a return of about £400 as currently I pay £54/month dual gas/electric on my fixed contract. It was knowing that that cost will only continue to rise that has made me look at how I can reduce costs after retirement.
Rogerblack - fortunately I won't have to borrow the cash, and unless something drastic happens to my pension poy I think I will stay above benefits level. I think the house was rated as D when I moved in 3 years ago but not sure. Since then anyway I have had cavity wall and extra loft insulation.
Martyn1981 - I'm afraid it was reading your thread mentioned that confused me - sorry - information overload I think. The 10 panels will fill the entire SE roof but I also have smaller South and SW facing rooves for an "L" shape - the offshoot kitchen and the back of the building is a real suntrap. The guy yesterday said that the panels actually work less efficiently if they get too hot and that SE was better than South - was he just spinning me a line? I will make sure the next ones consider that and price it - I think from my reading it would be better to have 2 inverters in that case - is that right? BTW the quote was for a bit less that 4grand but for Ulica panels (or Samsung for fixed period on sale) - Bosch ones would be 2 thousand more, but he said the cheaper ones worked just as good.
Lastly, as a bungalow surrounded by bungalows and with no large trees close by the roof gets very little shade so that's a bonus.

rogerblack

dreaming wrote: »

The guy yesterday said that the panels actually work less efficiently if they get too hot and that SE was better than South - was he just spinning me a line?

They are in fact less efficient - the output drops perhaps 1% for ever 3C rise or so.
But, not to the degree to make SE better than south.
If you have two sets of panels on different roofs, the inverter needs to cope with this - some are designed for this, so you don't need two inverters.

Martyn1981

Hello dreaming. Everything Roger said, spot on, also sorry for overloading you on the FAQ thread.

A south system will always do better, yes hot panels lose a bit of efficiency, but will generate much more than cooler panels not getting as much direct sunlight.

Splitting a system is not that bad at all, especially since you have a bungalow, so access will be easier. My ESE system has two inverters, but I really wouldn't recommend that. As Roger says, some inverters are designed to run two strings of panels separately. These inverters will have 2 MPPT's (max power point trackers). If you have panels that generate differently, such as differing roof orientations, or in my case different roof pitches, then each string of panels will need its own MPPT.

Don't be scared by this, the larger high quality inverters will have 2MPPT's. The only consideration being that each string will have a minimum size to meet minimum voltage, probably about 6 panels, so 6 + 10 good, 8 + 8 good, 4 + 12 not good.

My other system (the WNW) is a little more complex with a special inverter, that talks to individual power optimisers (PO's) on each panel. These help sort shading problems, but also allow for complex set ups with panels spread over differing roofs, orientations, pitches etc. The major issue is that the PO's are on the roof, making access tricky if one fails (they do have a 25 year warranty), but since you have a bungalow - no worries.

Don't rush, you've got plenty of time. The current tariff of 15.44p will remain till 30/4/13, and if my understanding is correct, it will also be extended till 31/7/13. [It gets reduced based on the number of installs in the quarter 3-6 months earlier, and it looks like installs up to 31/1/13 did not hit the amount required to reduce it further, but if I hear different I'll post it on the FAQ thread.]

Again, sorry to throw lots at you, but sounds like the world is your oyster, and you should be able to fit a 4kWp system, with all panels getting good levels of sun - certainly better than some of mine get.

Mart.

dreaming

Martyn1981 wrote: »

Again, sorry to throw lots at you, but sounds like the world is your oyster, and you should be able to fit a 4kWp system, with all panels getting good levels of sun - certainly better than some of mine get.

Mart.

Well thanks to the answers on here and copious reading I feel a bit more confident now. The quote at the weekend was for 2.5 kw (10 panels) but the guy did not mention using the other areas. That quote has come in at 3,650 but am now concerned because he didn't suggest more panels - did he just go for the easy option instead of really considering the aspect?
Quote tonight was for 4kw (8 panels on SE roof/8 on SSW as he measured it) with a split inverter for 7,999. The return on this would actually be more than I now pay for my dual gas/elec. bill (490.62 FITS/71.49 export pyt/228.78 reduction in annual energy) -can this really be? And is 8 grand a good price? I have 2 more coming this week so will have something to compare like for like but getting quite excited now

Martyn1981

Hiya Dreaming, after reverse engineering that FIT figure, that seems to suggest an estimated annual generation of 3,177 units. That can quickly be checked using PVGIS (that damned FAQ thread again!!!). But if you don't mind mentioning your rough location, just nearest town/city I'm happy to have a quick play.

Assuming you can split your system SE + SSW, then that will give you a nice long generation, starting slightly earlier than a south only, and finishing slightly better too.

As you have a bungalow, and I'm assuming roof access isn't too tricky (?) then I'd have thought £8k was very steep. Hopefully you'll get some quotes around £6k or less. People have mentioned numbers in the mid and low £5k's, but you'll have to compare the kit. Good quality inverters for a 4kWp system will mostly have dual MPPT anyway, so don't think that a split system should be much more expensive, if at all.

Leccy savings of £228pa - doubt it! It might happen, but probably beyond most people. I'd estimate low, around £100, but hope for better. My original 3.6 system is saving me about £150pa but I do work at it, and can vary usage during the day.

I think that's everything, for now.

Mart.

Edit. Knew I'd missed something. £3,650 for 2.5kWp doesn't sound bad at all. Taking that up to 4kWp might be £1,500 more, hard to say, but worth asking for his(?) thoughts / quote. M.

dreaming

Martyn1981 wrote: »

Hiya Dreaming, after reverse engineering that FIT figure, that seems to suggest an estimated annual generation of 3,177 units. That can quickly be checked using PVGIS (that damned FAQ thread again!!!). But if you don't mind mentioning your rough location, just nearest town/city I'm happy to have a quick play.

Assuming you can split your system SE + SSW, then that will give you a nice long generation, starting slightly earlier than a south only, and finishing slightly better too.

As you have a bungalow, and I'm assuming roof access isn't too tricky (?) then I'd have thought £8k was very steep. Hopefully you'll get some quotes around £6k or less. People have mentioned numbers in the mid and low £5k's, but you'll have to compare the kit. Good quality inverters for a 4kWp system will mostly have dual MPPT anyway, so don't think that a split system should be much more expensive, if at all.

Leccy savings of £228pa - doubt it! It might happen, but probably beyond most people. I'd estimate low, around £100, but hope for better. My original 3.6 system is saving me about £150pa but I do work at it, and can vary usage during the day.

I think that's everything, for now.

Mart.

Edit. Knew I'd missed something. £3,650 for 2.5kWp doesn't sound bad at all. Taking that up to 4kWp might be £1,500 more, hard to say, but worth asking for his(?) thoughts / quote. M.

Thanks Martyn. The figs tonight were 1716.8 for the SE facing and 1460.8 for the other - I'm in Northampton. The inverter is priced at £1200 for a Samil4000 (I think). 6grand would be much better than 8!
I wondered a bit about the elec. saving but I guess that would be down to me to adapt how I use it. I think I am pretty good with it but I do sometimes forget and leave stuff on when I'm not using it.
I have e-mailed the other guy and asked him about having the extra-will see what he comes up with. Just concerned that he didn't mention it. The one tonight was definitely a "salesman" but seemed more on the ball about positioning the panels.
Have contacted someone mentioned by Oscargrouch so will see what they have to say.