Estimated bill savings from solar panels

SkySi

I posted this in the "energy" forum but it was suggested I post here to get more expert opinions on solar panel savings.

I've just been reading the "Solar panels – are they worth it?" article and was surprised to see that the predicted electricity bill savings is in the range of £104 to £372 over a year depending on various factors.  Even the maximum saving of £372 seems incredibly low!  I was under the impression that assuming you have enough panels they should cover the majority if not all of your electricity usage.

According to the calculators on OVO (our current gas and electric supplier) and "makemyhousegreen.com" the yearly saving if we have 12 panels and a battery would be £1370 or £1650 respectively.  If we went up to 23 solar panels (theoretically) the yearly saving would be £2370 which is our entireyearly electric bill.

I know the actual savings could vary hugely depending on the size of the battery, weather etc. and that the companies selling the panels are going to want to give an inflated prediction of the savings possible, but even so the estimated maximum savings on that article seem incredibly low.  So my question is am I missing something when comparing this to the quotes I've been given?

lisyloo

Is this a duplicate post?
You won't produce enough in the winter and having a battery won't really help that.
here's mine as an example

Screwdriva

Some approximate numbers I use based on my own system's performance.

Expected annual generation - 6000kWh per annum

Amount earned/ saved per kWh via Octopus Flux (this may vary depending on region) - 18p per kWh

6000 * .18 = ~Between £1050 - £1100 per annum. A system capable of generating 6000 kWh should cost no more than £6700 fully installed. That should see a >15% return, tax free for decades. 

MallyGirl

I have only had my setup since mid March, and only been paid for export since early April.
I received a generation prediction based on the panels which has been exceeded every month so far.

Bills are looking good so far - obviously the weather could be different for the same month from year to year:
April 2023 - £209, April 2024 - £67
May 2023 - £112, May 2024 - -£42
June 2023 - £98, June 2024 - -£104
July 2023 - £101, July 2024 - -£63

Martyn1981

The problem is that there are many variables when looking for a generic figure, rather than one for your specific circumstances. Hence the broad range of estimates.

Here are some purely theoretical scenarios:

1 - You generate about 4,000kWh pa, from say a 4kWp install facing south in a good location, through to a 6kWp system mounted on E and W roofs, further north and with shading.

Your demand is low, and you make no efforts to maximise potential, so consume 1/3rd (1,333kWh), and export 2/3rd (2,667kWh). You save 25p/kWh on import, and export at a poorish 5p/kWh.

So savings + earnings are ~ £466 (£333 + £133)

2 -  You generate about 6,000kWh pa, (as above but with a larger system of say 6kWp (or 8kWp E/W)).

Your leccy demand is medium, and you make more efforts to use the PV during the day, consuming 45% and exporting 55%. Again saving 25p on import and perhaps a better export deal of 7p. 

So savings + earnings are £906 (£675 + £231)

3 - Generate 7,000kWh from a larger system again, and have a ~10kWh battery.

Leccy consumption high, plus the battery allows for time shifting some excess. So you consume 80%, and export 20%. Import 25p, and export 15p*.

So savings + earnings are £1,610 (£1,400 + £210)

*Current rate on Octopus but their are conditions, and maybe rates will drop in the future.


Hope this helps purely to demonstrate some of the variations. Also worth considering battery separately, that's to say work out the potential benefits without the battery, and then with the battery on top, as batteries cost a lot, so the additional savings need to be considered almost as a separate exercise to see if it's worth doing.

SkySi

Thanks all!  From the sounds of it the savings stated in that article are hugely underestimated.  From all of your examples it sounds like I should be saving several times the maximum amount stated in the article.  I'd be interested in where the author got their figures from.

Our electric usage is high so I'm not expecting to fully cover the usage in winter but if it can cover the majority of the summer electricity and a decent chunk of the rest it'll still be well worth the investment for us.

SkySi

Martyn1981 said:

The problem is that there are many variables when looking for a generic figure, rather than one for your specific circumstances. Hence the broad range of estimates.

Here are some purely theoretical scenarios:

1 - You generate about 4,000kWh pa, from say a 4kWp install facing south in a good location, through to a 6kWp system mounted on E and W roofs, further north and with shading.

Your demand is low, and you make no efforts to maximise potential, so consume 1/3rd (1,333kWh), and export 2/3rd (2,667kWh). You save 25p/kWh on import, and export at a poorish 5p/kWh.

So savings + earnings are ~ £466 (£333 + £133)

2 -  You generate about 6,000kWh pa, (as above but with a larger system of say 6kWp (or 8kWp E/W)).

Your leccy demand is medium, and you make more efforts to use the PV during the day, consuming 45% and exporting 55%. Again saving 25p on import and perhaps a better export deal of 7p. 

So savings + earnings are £906 (£675 + £231)

3 - Generate 7,000kWh from a larger system again, and have a ~10kWh battery.

Leccy consumption high, plus the battery allows for time shifting some excess. So you consume 80%, and export 20%. Import 25p, and export 15p*.

So savings + earnings are £1,610 (£1,400 + £210)

*Current rate on Octopus but their are conditions, and maybe rates will drop in the future.


Hope this helps purely to demonstrate some of the variations. Also worth considering battery separately, that's to say work out the potential benefits without the battery, and then with the battery on top, as batteries cost a lot, so the additional savings need to be considered almost as a separate exercise to see if it's worth doing.

Thanks for this.  Even your "worst case scenario" estimate is well over the maximum saving suggested in that article!  I don't think the numbers in the article can be right!

Martyn1981

SkySi said:

Martyn1981 said:

The problem is that there are many variables when looking for a generic figure, rather than one for your specific circumstances. Hence the broad range of estimates.

Here are some purely theoretical scenarios:

1 - You generate about 4,000kWh pa, from say a 4kWp install facing south in a good location, through to a 6kWp system mounted on E and W roofs, further north and with shading.

Your demand is low, and you make no efforts to maximise potential, so consume 1/3rd (1,333kWh), and export 2/3rd (2,667kWh). You save 25p/kWh on import, and export at a poorish 5p/kWh.

So savings + earnings are ~ £466 (£333 + £133)

2 -  You generate about 6,000kWh pa, (as above but with a larger system of say 6kWp (or 8kWp E/W)).

Your leccy demand is medium, and you make more efforts to use the PV during the day, consuming 45% and exporting 55%. Again saving 25p on import and perhaps a better export deal of 7p. 

So savings + earnings are £906 (£675 + £231)

3 - Generate 7,000kWh from a larger system again, and have a ~10kWh battery.

Leccy consumption high, plus the battery allows for time shifting some excess. So you consume 80%, and export 20%. Import 25p, and export 15p*.

So savings + earnings are £1,610 (£1,400 + £210)

*Current rate on Octopus but their are conditions, and maybe rates will drop in the future.


Hope this helps purely to demonstrate some of the variations. Also worth considering battery separately, that's to say work out the potential benefits without the battery, and then with the battery on top, as batteries cost a lot, so the additional savings need to be considered almost as a separate exercise to see if it's worth doing.

Thanks for this.  Even your "worst case scenario" estimate is well over the maximum saving suggested in that article!  I don't think the numbers in the article can be right!

Yeah, there seems to be quite a bit of negativity in many estimates of late.

Don't get me wrong, I always feel we should err on the side of caution, especially when offering advice to folk about PV. Last thing anyone wants is to be misled, or to accidentally mislead. I know price rises are in the news at the moment, presumably because UK leccy prices are linked to gas generation costs, and winter gas consumption will push up prices - but longer term, prices should continue to fall back down.

After allowing for general inflation, perhaps a longer term estimate of savings should be based on 20p import and 5p-10p export? At least that way you have a low ball estimate to help judge if it's a good investment.

And PV, is a slightly strange 'creature' since there are two different prices for the product - import savings, or export earnings. So a higher leccy user, actually gets to save more. And someone with extremely low consumption, perhaps a green superstar, would save far less, and might not even be financially sensible (ignoring any green & ethical pluses).


But putting my waffle aside, your best move is to get some quotes, so you can see what sort of system can be installed, and from there you will be in a reasonably good position to estimate savings against the cost. Folk on here can help with guidance and suggestions, and give opinions on prices.

SkySi

Martyn1981 said:

SkySi said:

Martyn1981 said:

The problem is that there are many variables when looking for a generic figure, rather than one for your specific circumstances. Hence the broad range of estimates.

Here are some purely theoretical scenarios:

1 - You generate about 4,000kWh pa, from say a 4kWp install facing south in a good location, through to a 6kWp system mounted on E and W roofs, further north and with shading.

Your demand is low, and you make no efforts to maximise potential, so consume 1/3rd (1,333kWh), and export 2/3rd (2,667kWh). You save 25p/kWh on import, and export at a poorish 5p/kWh.

So savings + earnings are ~ £466 (£333 + £133)

2 -  You generate about 6,000kWh pa, (as above but with a larger system of say 6kWp (or 8kWp E/W)).

Your leccy demand is medium, and you make more efforts to use the PV during the day, consuming 45% and exporting 55%. Again saving 25p on import and perhaps a better export deal of 7p. 

So savings + earnings are £906 (£675 + £231)

3 - Generate 7,000kWh from a larger system again, and have a ~10kWh battery.

Leccy consumption high, plus the battery allows for time shifting some excess. So you consume 80%, and export 20%. Import 25p, and export 15p*.

So savings + earnings are £1,610 (£1,400 + £210)

*Current rate on Octopus but their are conditions, and maybe rates will drop in the future.


Hope this helps purely to demonstrate some of the variations. Also worth considering battery separately, that's to say work out the potential benefits without the battery, and then with the battery on top, as batteries cost a lot, so the additional savings need to be considered almost as a separate exercise to see if it's worth doing.

Thanks for this.  Even your "worst case scenario" estimate is well over the maximum saving suggested in that article!  I don't think the numbers in the article can be right!

Yeah, there seems to be quite a bit of negativity in many estimates of late.

Don't get me wrong, I always feel we should err on the side of caution, especially when offering advice to folk about PV. Last thing anyone wants is to be misled, or to accidentally mislead. I know price rises are in the news at the moment, presumably because UK leccy prices are linked to gas generation costs, and winter gas consumption will push up prices - but longer term, prices should continue to fall back down.

After allowing for general inflation, perhaps a longer term estimate of savings should be based on 20p import and 5p-10p export? At least that way you have a low ball estimate to help judge if it's a good investment.

And PV, is a slightly strange 'creature' since there are two different prices for the product - import savings, or export earnings. So a higher leccy user, actually gets to save more. And someone with extremely low consumption, perhaps a green superstar, would save far less, and might not even be financially sensible (ignoring any green & ethical pluses).


But putting my waffle aside, your best move is to get some quotes, so you can see what sort of system can be installed, and from there you will be in a reasonably good position to estimate savings against the cost. Folk on here can help with guidance and suggestions, and give opinions on prices.

Thanks I really appreciate the advice!  I'll definitely get a few quotes and go from there.

NedS

I started out by looking at the PVGIS estimated annual generation for any proposed solar system here (which is surprisingly accurate)

https://re.jrc.ec.europa.eu/pvg_tools/en/

I am on Octopus Agile, and Octopus pay me 15p SEG for any exported electricity.

Because it is difficult to estimate how much of your solar generation you will use (reducing your bill by your unit rate per kWh) and how much you will export to the grid (at 15p per kWh in my case), I assume a flat rate of the SEG amount of 15p per kWh.

PVGIS says my 3.64kWp array will generate around 3500kWh per year, so I estimate that is worth in the region of £525 per year, as a combination of reduced import usage and SEG credits to my account. For me, I think this is a reasonably accurate estimate.

Adding a battery makes the calculation more complex. If you use excess solar to charge a battery for later use, you immediately give up the 15p SEG, so you are now only saving the difference between the import price when you use the battery storage and your SEG rate. If you charge your battery from the grid, then your input costs are the unit rate you charge at. Don't forget to include any losses for charging and discharging your battery plus inverter losses converting between AC and DC, as these may be significant. For me, the financial case for a battery is a lot less clear cut whereas a solar array is likely to make a lot more financial sense.

Magnitio

We've had solar and battery installed for 2.5 years (details below) and savings were £1,691 in year 1, £1,670 in year 2 and £859 so far this year. As this exceeds our annual energy bill, we are currently in credit by £600 and had a refund of £400 last year. It does help that we have an EV and therefore access to a tarrif that allows charging the house battery at 7p/kWh and selling excess solar at 15p/kWh.