Should I invest in solar? And if so how?

busybee100

I'm in a quandary.

We are a household of two, mostly at home all day. The property is in Cornwall with no obstructions.

We only use 2000 units a year electricity (with effort) and 4000 gas. We have no EV and no plans to get one for a few years but had no power for two or three days last year because of the storms.

Eonnext suggest 14 panels on the roof (which is pan tiles and prone to moss).

If it still sounds like a good idea should it be a cheap system? We also have a difficult neighbour so may have to move although our youngest is returning next year for a while so it will be a couple of years yet.

TIA

Screwdriva

If the entire centre building is yours, that looks like a lovely South East facing roof aspect. Your annual consumption is too low to justify a battery but should easily fit 20 X 515W Eurener bifacial panels paired to a SolarEdge 10kW inverter with optimizers and a 20 year inverter warranty, for around £8K installed.

Assuming you generate 9000 kWh per year, the system should 'earn' you ~£1200 or so per annum (a combination of savings and export earnings) . That a ~7 year/ 14% return on your investment.

Reed_Richards

….had no power for two or three days last year because of the storms.

You might imagine that solar panels will help when you have no mains power but they won't. That's because the device that controls the panels, the "inverter" needs power to start up and that has to come either from the mains or from a battery. If you get a battery along with your panels you still won't have power when there is a mains power cut unless you have a special device fitted that isolates your house from the mains. That is necessary to safeguard anyone working on the mains wiring that supplies your house and stop them being electrocuted by electricity sent down the mains wiring from your panels. You should be able to get your installer to include a battery and the isolation device but both will cost you extra.

busybee100

https://forums.moneysavingexpert.com/discussion/comment/81966388#Comment_81966388

No it's only half the building, it's about 10m long. Does that mean it would be 10 panels and we would 'earn' about £600 per year? That should nearly cover what we pay for electricity now?

I think I really don't know enough about the recompense for exporting to the grid. I hear people complain about the returns or having to choose between a good export rate or a low overnight tariff. It never sounds attractive.

busybee100

https://forums.moneysavingexpert.com/discussion/comment/81966467#Comment_81966467

Thank you for this, I will make sure to ask when I get someone out to have a look.

Is there a minimum size battery required? I guess there wouldn't be much electricity generated during a storm anyway so maybe that's not important. To protect us from no power I would then need a decent size battery but could then also have the heating on. We spent two days in coffee shops and pubs last year.

QrizB

If you just want a battery as a standby, you don't need to spend £4k+ on a grid-tied one. A chunky power bank plus a changeover switch would probably do the job for under £1000 and provide enough power to run a gas central heating system.

See an example in this video, starting at the 12 minute mark:

https://youtu.be/qzwNVHGdU9Q

Other makes and models of power bank are available and have similar functions, you don't need to choose an Ecoflow.

(You could even be cheeky and use a plug-in battery, the sort of thing that is popular in Germany for use with plug-in solar. But those aren't yet authorised in this UK.)

The problem then is that the battery won't charge from solar, so if it goes flat before the power comes back on you'll need to find somewhere to charge it.

A proper grid-tied battery that integrates with your rooftop solar is the deluxe solution, but financially it might not make sense.

Reed_Richards

YEAR	Solar	Funds	Invest at 4%
0	£0.00	-£8,000.00	£8,000.00
1	£1,200.00	-£6,800.00	£8,320.00
2	£2,448.00	-£5,552.00	£8,652.80
3	£3,745.92	-£4,254.08	£8,998.91
4	£5,095.76	-£2,904.24	£9,358.87
5	£6,499.59	-£1,500.41	£9,733.22
6	£7,959.57	-£40.43	£10,122.55
7	£9,477.95	£1,477.95	£10,527.45
8	£11,057.07	£3,057.07	£10,948.55
9	£12,699.35	£4,699.35	£11,386.49
10	£14,407.33	£6,407.33	£11,841.95
11	£16,183.62	£8,183.62	£12,315.63
12	£18,030.97	£10,030.97	£12,808.26
13	£19,952.21	£11,952.21	£13,320.59
14	£21,950.29	£13,950.29	£13,853.41

Another way of looking at the investment (based on @Screwdriva's figures) is to compare what happens if you invest your £8000 in a savings account with what happens if you get solar panels. If you take £8000 and invest it at 4% p.a. then after 14 years your money will have grown to £13,853 if you just leave the money to earn compound interest. If instead you buy solar panels, these save you £1,200 each year and at the end of each year you put this £1,200 into a savings account earning 4% interest then after 14 years you will have £13,950 in that savings account and, if it's still going, a solar panel system saving you £1,200 per year.

Of course the £1,200 saving per year is not really fixed, it will tend to increase if electricity prices increase and it will tend to decease if the amount you are paid for your export decreases. Both seem to be the current trend. The interest rate you can get on savings could go up or down. And if you sell the house, will your panels enhance its value? An Estate Agent might be able to advise on that one.