Low Elec Usage - Should I consider Solar Panels?

n15h

Hi all,

Over the last week I've been researching in having PV solar panels installed now since WFH permanently. My usage is very low at 1100 kWh a year (2 bed semi detached, only 1 person in property in Midlands). Roof at front faces East, and back faces West.

I'm thinking 6 x 250w panels should be placed as 3 on front roof, and 3 on back roof. Also been looking at whether a battery is a good investment (for storage so that some of the electricity generated during the day is stored to use in evenings/night). I haven't had any quotes yet, but researching online, I am estimating cost of £4K for panels, inverter, battery and installation. I would have the panels installed privately so that I would own them outright, rather than lease which I know in some cases makes it difficult to sell the property in future (if I chose to sell).

I've also used the below website to get an idea of how much kWh an installed peak power of 1.5 (250 x 6 / 1000) would generate with a system loss of 25%. The website calculates yearly PV energy production of 1246kWh, with variability of 50kWh, which would still mean enough elec for my use is generated. 

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

I'm sure there are more knowledgeable people on these forums that can provide guidance and whether it is worth considering. Any suggestions or guidance on any website/sources of info would be also appreciated.

mcgrimes

You use about £200 of electric a year. Assuming you cover 50% of your use, then 50% goes back to the grid at about 5p/kWh.
So (200x0.5) = £100 energy saving
0.5x1246x5p = £31
so a yearly saving of £131.
you might need an inverter after 10 years at £80p, knocking 5 years of savings off.

You’ll never get your money back.

QrizB

n15h said:

I'm thinking 6 x 250w panels should be placed as 3 on front roof, and 3 on back roof. Also been looking at whether a battery is a good investment (for storage so that some of the electricity generated during the day is stored to use in evenings/night). I haven't had any quotes yet, but researching online, I am estimating cost of £4K for panels, inverter, battery and installation. I would have the panels installed privately so that I would own them outright, rather than lease which I know in some cases makes it difficult to sell the property in future (if I chose to sell).

A few thoughts:

• Six panels, 1.5kWp, is a small system. Splitting them across two aspects makes two very small systems. If you're going to all the cost and effort of scaffolding a roof, you should consider fitting more panels as the incremental cost will be small.
• Almost no-one fits 250W panels any more, the smallest size commonly offered is 330W.
• A battery is rarely a good idea for a small user. You can add one later if your situation changes.
  

In terms of cost, you're looking at a minimum of about £4k to get any size of system installed across two roofs, and that's without a battery, but that could get you a total of 3kWp and generate 2500kWh/yr. It might save you £60/yr on your electricity bill and earn £100/yr in export payments. Payback would be 25 years.

A battery would add £2k and save an extra £60/yr. Payback on the battery would be 33 years (roughly 3x its working life).

Or you could eg. invest your £6k into a renewable energy fund in a SSISA.

arty688

Other variables to consider are
Octopus Agile export which is especially good for West roofs.
If you have a car the chances are it will be electric in the next few years increasing your consumption.
Prices are likely to go up
The feeling of generating your own electric.

Verdigris

There are several more-or-less fixed costs in a solar PV installation - scaffolding, getting the crew to site etc. You will get better value for money by installing as large an installation, up to the normal 4kWp limit for standard domestic installations.

If you get a smart meter and subscribe to a SEG deal with a supplier you will get some income from any electricity you cannot use. If your main heating is by gas, you could add an immersion diverter to get your summer hot water from the panels and probably not use any gas at all in the warmer months.

silverwhistle

I concur with the general opinion: go larger due to the fixed costs and no battery now. If you can, get a diverter for the immersion - it's done my hot water to now since March, and a timeswitch or two if you want to kick off a washing machine or the like during the day when you aren't there. My dishwasher and many other appliances have delay timers which can be useful.

n15h

Hi everyone, thank you very much for the comments! It does seem logical to have more panels fitted. Good to also know about the immersion diverter, as currently I have a combi boiler (3 years old) which is used for hot water / heating.

I thought it would make sense to have a battery from the start, but it does also make sense to maybe consider installing it in future. I currently have my energy provided by Octopus, and I believe they are also a SEG supplier.

ABrass

I say don't bother. Your electricity use is so small it won't pay back within a reasonable period. Diverters are entertaining, but they don't save you much money in practice and they cost more to install.

If you get an EV, get the panels then. They are likely to be even cheaper by then.

Solarchaser

I would say solar could be useful on the export tarrifs as mentioned by arty.

A battery will never be of any use to you being such a low consumer.

If you go solar, go the largest you can fit on your rooves and hope for decent export tarrifs.

Unless gas prices increase, a diverter would lose you money over an export tarriff.

n15h

I thought that a battery would make sense as it would be charged up with elec generated by the PV panels and then i would use that elec, while the PV would continue to charge it and export any electricity out once the battery is full. That way, by continuously charging/exporting, I could effectively power the house electrically from March-September without using electricity from the grid.

I'm guessing in reality, that is not the case, even if i am a low user, have a PV set up that gives 2000 kwh annually, and a battery that can hold 3-4kwh daily.

QrizB

n15h said:

...I could effectively power the house electrically from March-September without using electricity from the grid.
I'm guessing in reality, that is not the case, even if i am a low user, have a PV set up that gives 2000 kwh annually, and a battery that can hold 3-4kwh daily.

You're probably right, it would work and you could be self-powered for 6 months of the year. The problem is that with current battery prices there's pretty much no way it would pay for itself.

1100kWh/yr is roughly £230 for electricity plus £90 standing charge, call it £320 per year. If you were entirely off the grid, this is the maximum you could possibly save.

Being self-powered for 6 months might save you half of the £230, so £115 per year (you'll still need to pay the standing charge). A 4kWh battery like this will cost you £3000 (it will be a little bit cheaper if you use a hybrid inverter for the solar PV). The man-maths just don't work.