Solar Panel Q&A

[albie]

BST,

Of course I read your post.
You argued the point I am making in reply 79, then reverse your position to say that electricity prices do not effect the outcome!

So what do we think the current saving per year is Vs cost to install? I still struggle with the payback period if I'm honest.

Depends on how the price of grid electricity goes of course.

At the moment, with current tariffs and some pretty active use of when to charge and discharge batteries, I reckon I've got about a 9-10 year payback period.

My advice to anyone thinking about this is to get the very largest set of panels possible. With hindsight, I wish I'd realised this when I had the panels fitted. With a bit more thinking about the layout, I could have got 13 rather than 10 panels on my roof. I was quoted £200 Inc VAT for each additional 400W panel at installation. From the figures I've got so far, I reckon each panel will produce at least 300Wh per year. At 15p feed in tariff, that's less than 5 years payback period for the additional panels. If you use that extra to offset importing from the grid, the payback period is only just over 2 years.

The argument you later make about averages is beside the point, because the situation is evolving very quickly.
We can hold different opinions without difficulty in my book.

[Superspy]

The batteries made a huge difference to the Energise Barnsley project I did. We fitted OAP bungalows with solar pv, and despite the tenants  mainly being in all day, utilisation was only around 45% of generation, and that was with an education piece on how to get the most out of the free power.  Adding just a 3kW battery took utilisation to over 75%, plus set up as a virtual power plant gave DSR and arbitrage opportunities.

That's an awesome real world example.

For my part, my EV has now arrived on Tuesday (yay!) so my utilisation has gone through the roof. For this week I'm at 88.5% - 135.5 generated, 15.6 exported.

[Superspy]

The batteries made a huge difference to the Energise Barnsley project I did. We fitted OAP bungalows with solar pv, and despite the tenants  mainly being in all day, utilisation was only around 45% of generation, and that was with an education piece on how to get the most out of the free power.  Adding just a 3kW battery took utilisation to over 75%, plus set up as a virtual power plant gave DSR and arbitrage opportunities.

That's an awesome real world example.

For my part, my EV has now arrived on Tuesday (yay!) so my utilisation has gone through the roof. For this week I'm at 88.5% - 135.5 generated, 15.6 exported.

In a couple of weeks I'll be integrating an EV charger with the Solar to automate some of the manual monitoring I'm having to do at the minute to get the best out of it all.

[BillyStubbsTears]

BST,

Of course I read your post.
You argued the point I am making in reply 79, then reverse your position to say that electricity prices do not effect the outcome!

So what do we think the current saving per year is Vs cost to install? I still struggle with the payback period if I'm honest.

Depends on how the price of grid electricity goes of course.

At the moment, with current tariffs and some pretty active use of when to charge and discharge batteries, I reckon I've got about a 9-10 year payback period.

My advice to anyone thinking about this is to get the very largest set of panels possible. With hindsight, I wish I'd realised this when I had the panels fitted. With a bit more thinking about the layout, I could have got 13 rather than 10 panels on my roof. I was quoted £200 Inc VAT for each additional 400W panel at installation. From the figures I've got so far, I reckon each panel will produce at least 300Wh per year. At 15p feed in tariff, that's less than 5 years payback period for the additional panels. If you use that extra to offset importing from the grid, the payback period is only just over 2 years.

The argument you later make about averages is beside the point, because the situation is evolving very quickly.
We can hold different opinions without difficulty in my book.

Albie

Look at my post 76. The "averages" I was talking about are domestic PV production and domestic and EV usages.

That's the post that you haven't taken on board.

The simple fact is that, on average, domestic PV can only produce enough power to service both average domestic consumption and average EV need on the very best days of the year.

I'll repeat. For most people, on average, getting imported electric from the grid is vital if you want to have an EV. There's no getting round that by talking about electricity prices or times of production or times of usage. It's just a basic fact.

[BillyStubbsTears]

Just finished my first full month of getting feed in tariff.

With the amount of electricity we've used, the usual bill if everything was coming from the grid at standard rates would have been £132, including the standing charge. Actual bill has been minus £5.70.

OK, so June is probably the best month of the year for solar, but I'm well pleased with that.

And tomorrow afternoon, the Octopus Agile rate is as low as minus 18p/kWh. So instead of you paying 30p/kWh, they are paying you 18p to take the electricity off them.

[drfchound]

Not trying the “oneupmanship” line but my electric bill including standing charges for the last month was £12.38 and I exported £72.56 back to the grid.
My account is with Octopus.

[Superspy]

I don't tend to look at my actual bill at the minute as I know I'm exporting more than I'm using, so I'm just making a direct debit of £1 a month into my Octopus account to keep the dd going. I just tend to look at my generation and utilisation numbers to get an overall monthly benefit amount.

So for me June looks like this:

Generated and used: 710.6 kWh = £229.95
Export: £52.33
Cheap-rate charging offset: £11.42

For a total benefit in June of £293.70

That means I'm at approx £1150 saving since November, so I'm on for a year 1 saving of approx £1800. If that lands I'll definitely be happy but should likely also beat it next year by being on an EV specific tarriff over the winter months.

[drfchound]

I don't tend to look at my actual bill at the minute as I know I'm exporting more than I'm using, so I'm just making a direct debit of £1 a month into my Octopus account to keep the dd going. I just tend to look at my generation and utilisation numbers to get an overall monthly benefit amount.

So for me June looks like this:

Generated and used: 710.6 kWh = £229.95
Export: £52.33
Cheap-rate charging offset: £11.42

For a total benefit in June of £293.70

That means I'm at approx £1150 saving since November, so I'm on for a year 1 saving of approx £1800. If that lands I'll definitely be happy but should likely also beat it next year by being on an EV specific tarriff over the winter months.

I only had my solar and ASHP fitted last November so haven’t yet had a full year to do a meaningful comparison to previous years.
Also, my two year fixed deal ends this month so that will make it further difficult.
However, the new Octopus tariff isn’t as high as I thought it was going to be so I am confident that the solar over twelve months will still be advantageous to me.

[Superspy]

Yeah mine was fitted in September but I wasn't on an export tarrif until November so I missed out on about 6 weeks...so I'm taking November to November as the first year. It feels more accurate that way. Another reason I don't focus on the bills is because comparing with previous years doesn't mean anything in my circumstance because my usage has changed hugely for a variety of reasons.

In terms of payback period you're better off if energy is more expensive - if by some miracle energy prices dropped to pre-Covid levels it would take a lot longer for your system to pay itself off.
An easy comparison based on last months figures is that £229.95 saving last month would be £207.94 for this month as a result of the unit price drop a couple of days ago.

[Filo]

What happens when your panels get covered in bird shit, I’ve got Wood Pigeons all over and any panels i would have will be covered in shit in no time

[Superspy]

Hope the rain cleans it off for you :D

[drfchound]

Yeah mine was fitted in September but I wasn't on an export tarrif until November so I missed out on about 6 weeks...so I'm taking November to November as the first year. It feels more accurate that way. Another reason I don't focus on the bills is because comparing with previous years doesn't mean anything in my circumstance because my usage has changed hugely for a variety of reasons.

In terms of payback period you're better off if energy is more expensive - if by some miracle energy prices dropped to pre-Covid levels it would take a lot longer for your system to pay itself off.
An easy comparison based on last months figures is that £229.95 saving last month would be £207.94 for this month as a result of the unit price drop a couple of days ago.

It took me about three months to get my export sorted but the first monthly payment was only £1.35 so I’m guessing that the winter months won’t be very good in that respect.
The summer months though look like being quite lucrative.

[Superspy]

Absolutely, here are my export figures since November:

Nov: £2.46
Dec: £20.28
Jan: £2
Feb: £4.80
Mar: £11.21
Apr: £64.09
May: £88.48
Jun: £52.33

December was an anomaly because it was quite a bright month and I filled the battery overnight a lot so ended up exporting significantly more than I otherwise would have.
June generated more but was a drop off in export due to me massively increasing my utilisation. My utilisation in May was 58% (493 kWh out of 843 generated), Jun was 80% (710 kWh out of 887 generated). I'm hoping to get that up towards 90% for July.

[BillyStubbsTears]

Those are some impressive numbers SS. They really demonstrate the benefit of going for a large system if you can.

The cost of an additional 400W panel in a system is about £200. I reckon each panel in my system will produce about 350kWh per year. At the 15p/kWh feed in rate I've got with Octopus, that means a payback period of about 4 years. Your 22p feed in tariff will cut that to less than 3 years. (Of course, those are the marginal figures for additional capacity, assuming the fixed costs are the same regardless of the system size.)

With our 10 panel system and relatively high usage, we got £35 feed in payment in June. That's much better than I expected. And taking advantage of low import costs to charge batteries meant that our payment for import was less than £20.

This weekend just gone was interesting. There was a huge plunge in import costs, down to as low as minus 18p/kWh. So we were able to get paid to charge up the batteries and consume, while also getting paid for discharging the batteries and exporting the solar production. I've not done the detailed numbers, but I reckon we will have been paid net about £8-10 just for Saturday and Sunday. As I say, it's not going to make anyone into a Great Gatsby, but it's a no brainer if you can do it. As well as doing a little bit to help the bigger climate challenge.

[albie]

Octopussy;
https://www.current-news.co.uk/octopus-smart-tariff-hits-record-price-plunge-as-electricity-prices-turn-negative/

[Superspy]

Something I thought may be interesting to those of you still following the thread.

I fitted an EV charger last week which has a solar integration where it can detect the surplus being generated by the panels and divert it to charge the car instead of exporting it back to the grid. Today has been the first day where it's been sunny enough to really put it to the test and the graph below shows the result. I thought it was pretty cool so wanted to share.

The 2 highlighted areas represent the EV charger automatically scaling the demand based on the surplus being generated - up before the midday peak and back down again at the other side.
Using a hybrid inverter (also a known as 'DC coupled' in terms of the battery) means that you can't directly distinguish between surplus coming from the panels vs the battery, so you have to set an export offset up...basically the EV charger targets exporting a small amount whilst the solar inverter/battery targets zero import/export, so when it detects that the export drops below the offset, the charger stops as it knows this is a result of solar generation drop off (all demand being supplied by the battery at that point. That's why the consumption line is always a little bit below the generation line.

[albie]

New tariff from Octopus which might be suitable for some with solar and batteries;
https://www.solarpowerportal.co.uk/news/octopus_launches_new_solar_and_battery_optimisation_smart_tariff

Lots of innovation around tariffs going off!

[BillyStubbsTears]

Just reviewed my system numbers now that I've had it for 7 months.

We are heavy users of electricity. The amount we have consumed in 7 months would have cost about £850, paying at standard tariff rates.

We've actually spent net £24.

It'll be interesting to see how this goes over the winter. Obviously there will be precious little solar production - my system is producing less than a quarter of our daily usage so far in October. But the increasing wind is leading to some very low Octopus Agile buy-in rates
 For example, last night, between 3-5am, the buy in price was 0.0p per unit. At the moment it is 2.3p. That compares with standard tariffs of about 30p. So we can effectively charge up the battery system for free and live off that.

Be interesting to see what the pay back time will be based on the first full year of use. I'm expecting about 8-10 years.

[BillyStubbsTears]

This is a useful website by the way. Real time data from National Grid on the amount of electricity being generated by coal, gas, wind, solar etc, plus the current market rate for electricity and the amount of CO2 generated per unit.

https://grid.iamkate.com/

[Ldr]

This is a useful website by the way. Real time data from National Grid on the amount of electricity being generated by coal, gas, wind, solar etc, plus the current market rate for electricity and the amount of CO2 generated per unit.

https://grid.iamkate.com/

Are you running an ev Billy? Be interested in your take on certain tarrifs I’m looking at

[BillyStubbsTears]

Ldr.

No. I don't have off street parking so I can't get a charger that would make me eligible for the low overnight Octopus tariffs. I'd do it like a shot if I could. It's a no-brainer.

How much electricity do you typically use?

[Superspy]

I was going to wait a little while to give my next update on here but seeing as BST has revived it early I'll jump in.

Our system has been up for a little over a year now, although we didn't get onto the export tariff until early November last year, so bear that in mind.
The savings from our system since installing it in mid September 2022 are a little under £1900, made up of £1310 of utilised generation, 340 quid in exports, and 240 quid in savings by charging the battery at a cheaper rate and using the leccy through the day.

Now that I've got an EV I've moved off the Flux tariff I was on previously and moved onto Octopus Go, to take advantage of the cheaper rate over night as I'm exporting very little.

Accounting for the lack of export tariff for the first 6 weeks of the system being up I reckon that puts our annual savings at around 2k. 6-7 years payback should be do-able at those kind of numbers, which would be awesome. Of course it's harder to calculate accurately now because of the EV - using more leccy but spending nothing on petrol - I'm choosing to believe that I'd have gotten the EV anyway (even if I didn't have the solar) so that I don't have to account for that in the numbers.

[Ldr]

Ldr.

No. I don't have off street parking so I can't get a charger that would make me eligible for the low overnight Octopus tariffs. I'd do it like a shot if I could. It's a no-brainer.

How much electricity do you typically use?

Currently around 6700 kWh per year with a phev

[BillyStubbsTears]

Ldr.

No. I don't have off street parking so I can't get a charger that would make me eligible for the low overnight Octopus tariffs. I'd do it like a shot if I could. It's a no-brainer.

How much electricity do you typically use?

Currently around 6700 kWh per year with a phev

I'm guessing most of your electric goes on the car? If it does, you'd be mad not to get the Intelligent Octopus tariff. 7.5p per unit overnight.

[albie]

Probably best to add this update here, as the thread contains more information.

New solar roadmap published today;
https://www.gov.uk/government/news/homeowners-could-save-hundreds-on-energy-bills-from-solar-drive

The big takeaway is that balcony solar panels are likely to be approved.
Very popular in Germany, you just hook them over the balcony, connect to the inverter, then plug in to the nearest socket.

Very easy DIY, and no scaffolding costs involved.
Guardian business coverage here;
https://www.theguardian.com/business/2025/jun/30/britons-could-soon-install-balcony-solar-panels-in-flats-and-rental-homes