Solar panels - are they worth it?

ladymarmalade1970

Hi,

We are moving to a house where we could have solar panels.

Are they worth buying and what about these free deals?

I don't really understand how it works. As in can you run the whole house off them and when/why do you sell it back?

Any help or pointers to other threads greatly appreciated.

Reed_Richards

Solar panels give you "free" electricity when the sun shines. You'll get the most output when they point full-on to the sun, some when it's a bit cloudy, very little if it's murkily cloudy and none when its dark. You won't come close to running the whole house off them unless you store electricity using a battery as part of the system. But batteries are very expensive and the economics of getting one are uncertain.

When the solar panels are facing the sun you will generate more electricity than you can use; even with a battery you are likely to do this. You used to be able to sell your spare electricity back to a provider at a price guaranteed by the government but that scheme was discontinued earlier this year and it is now down to individual electricity companies to decide how much they will pay. This has put paid to the "free deals" - which were never a good idea in the first place because you got a "sitting tenant" occupying your roof which can make your house difficult to sell.

ladymarmalade1970

Thank you Reed_Richards. So ruling out free deals and selling back. Is it worth investing for the free electricity? I think from what you have said it would take rather a long time to recoup the initial investment however i still like the idea of free energy.

Martyn1981

Hiya. If you have a look at the FAQ's (see my autosig) that'll give you the basics, though they are getting a bit out of date now.

Crucially it will depend on the price/quote you get. A recent thread was looking at £4.6k for 4.2kWp of PV and a diverter to put spare generation into a hot water tank. But you might find you get silly quotes of twice that.

Have a read, ponder, ask some questions etc etc, then perhaps get a few quotes and see what you think. Then ask on here for opinions, and so on, and so on.

Zarch

Since the removal of the feed in tariff generation payments in March the only real way to make Solar PV pay is asking yourself can you use the vast majority of what you're generating? So saving the 14p per unit you'd be paying to buy electricity otherwise.

Without the old generation payments you're left with export payments. Octopus will pay you 5.5p for each kWh you generate but don't use.

So say you have 4kW system installed generating 4000kWh per year and you use 50% of what you generate, you'd get paid for 50% sent back to the grid, so 2000kWh.

2000 x .055 = £110 per year in export payments.

You also need to you look at it from how much you'd also save. Those 2000kWh each year would have cost you approx 14p per unit if bought from your electricity supplier.

2000 x 0.14 = £280 per year saved.

So maybe close to £400 per year in that 50/50 scenario?

So back to the original question..... how much of what you generate can you use?

50 / 50 split might be very optimistic.

25% used / 75% exported brings the annual figure down to £140 saved + £165 exported (approx £300 per year).

As a 4kW system is likely to cost approx £4k its going to take maybe 10-14 years to get your money back in those two cases.

- Do you have an electric car you can charge in the day - that will use loads.
- Do you have a hot water tank that you can divert excess Solar to - that will use a lot.
- Do you have any other high electricity usage device? Air source heat pump etc?

Simple maths suggests that they more you can use, the quicker the payback period as saving 14p per unit is a better deal that getting 5.5p per unit.

And finally, obviously the initial outlay dictates the payback period.

No point paying way over the odds like £8k for a 4kW system as it turns the payment time into like 20+ years.

Hope this helps?

Reed_Richards

I was amongst the last to get on the Feed-in Tariff scheme. This gives me 3.79p per kWh generated plus 5.38p per kWh of electricity I export. The amount I export is deemed to be 50% of what I generate so in effect I get 6.48p per kWh generated or 12.96p for every kWh I am deemed to export. You can see that this compares very favourably with the 5.5p per kWh [STRIKE]generated[/STRIKE] exported that you might get now, as mentioned by Zarch. But you should not discount the money you can get paid for electricity you export because under the wrong circumstances (such as a house that is unoccupied 9 to 5) you might find that you export most of what you generate.

pinnks

Not sure I understand the maths in Reed's post?

If generation tariff is 3.79p and export is 5.38p, then with 50% deemed export you end up with an effective 6.48p for each kWh you generate (3.79 plus half of 5.38). Where does the 12.96p come in?

Most people without an immersion diverter will export way more than 50% over the year. I have 2 diverters and have been recording export for a number of years now.

Ignoring the diverters my export is over 60% https://www.dropbox.com/s/83vfyvlnjzb353a/myimmerSUN-no%20immersion%20or%20radsJPG.JPG?dl=0. Taking the diverter into account that feeds the immersion heater, export is about 45% https://www.dropbox.com/s/j513698him4vy40/myimmerSUN-no%20rads.JPG?dl=0 and taking both diverts into account (the second one powering 2 oil-filled radiators in the shoulder months) export is about 30% https://www.dropbox.com/s/47hcybpy9giaiez/myimmerSUN.JPG?dl=0.

If you factor this into this discussion then you would need an actual export payment of about 11p per kWh without a diverter. If you have a diverter then that rises to about 14p if I have my maths right.

To put it another way, if you generate 100kWh at 6.48p you get FiT of 648p. If you export 60% and get paid only for export you need to get just under 11p per exported kWh to get to 648p and with 45% export you need just over 14p to get to that amount...:beer:

Reed_Richards

pinnks wrote: »

Not sure I understand the maths in Reed's post?

If generation tariff is 3.79p and export is 5.38p, then with 50% deemed export you end up with an effective 6.48p for each kWh you generate (3.79 plus half of 5.38). Where does the 12.96p come in?
:

If you buy solar panels now you can get paid for what you export but not (AFAIK) what you generate. It seems outdated to think of what you are being paid for generation so I added 5.38p + 3.79p + 3.79p = 12.96p to calculate what I am paid for export.

Okay, that's deemed export but as I don't even have an immersion heater, let alone a diverter, I actually do export roughly half of what I generate. If I didn't have a battery I would be exporting a lot more without being paid any more for it.

Reed_Richards

ladymarmalade1970 wrote: »

We are moving to a house where we could have solar panels.

Something that has not been mentioned is the value that solar panels add to your house and it's not a lot, if anything at all. So if you are moving now and might be moving again in a few years then you are unlikely to recoup your solar panel investment.

KevinG

Reed_Richards wrote: »

Something that has not been mentioned is the value that solar panels add to your house and it's not a lot, if anything at all.

A lot of people say it subtracts value. It wouldn't for me but I'm probably not a typical buyer.

pinnks

My daughter was looking at a house with owned solar panels and battery and the survey came back with all sorts of spurious comments and conclusions but did not ask the crucial questions about ownership.

That didn't phase us and I found it incredible that the best part of a decade after panels started to be fitted the house buying/selling service sector still hasn't got its act together. Unfortunately daughter decided to withdraw for other reasons with the survey...