Solar Panels? Do we??

[Grimbelina]

Hi all, we have been given a lot of conflicting advice... but hope that the collective wisdom of MN will help!

We have just moved to a detached house and are about to build an office (6mx6m) that will have a pitched roof, one side south-facing so approx. space for panels of around 20 metres square on that side. We will have 1 or 2 hybrid cars so need to charge them and there are two of us at home working nearly every day.

Would it be worth us putting in the panels for the car(s) and to run appliances in the day?

We are also considering whether it would be worth running the underfloor heating off of it (know this is a different system though)?

We also have another area of flat roof which again is south facing on the main house, again around 20 metres square which we could put more panels (of which system I am not sure) to use for underfloor heating or electricity?

We plan to live here at least 10 years, perhaps more, will we get our money back? We can't insulate anymore than we have... but are slightly at a loss (and aware the solar panels themselves are difficult to recycle etc.) as to what to do?

Any experience/advice would be very gratefully received!

How much will they cost?

We looked into this when our council were offering a subsidy. Even with the subsidy the payback period was over 10 years. Solar panels don't even last that long before they need replacing so we didn't go ahead. Even with the recent energy price hikes I still don't regret that decision.

Unless your electric bill is close to £100/month I don't think you will see pay back over 10 years.

we have solar panels to charge the hybrid car

if you are doing it only to save money, it probably isn't worth it (but with gas prices skyrocketing etc, it might be).

we did it to be more eco-friendly and less reliant on the national grid. The installation was simple & the system works well. The savings will probably repay the installation cost but not give us much profit.

In financial terms, it won't be worth doing.

You could just charge the cars off-peak. It will likely take decades for the panels to pay for themselves.
They won't contribute anything worthwhile to any heating. Output of solar drops right off over winter (exactly when you'd want it for UFH)

Thanks everyone, it's a tricky one, would love to have them... but not so good if we never make the investment back and then move!

It depends on market forces, but I can only see the need for more solar panels. Whether you gain the benefit and stay to use it, or you move on and sell 'with the solar panels as a benefit' is the same net result IMHO. I'm house hunting vaguely and am very conscious of the EPC statement this time around, so I'm sure market forces will head further in this direction in the coming years, particularly if you have the electric car charging set up.

This has information that might be helpful, we're thinking about getting some fitted but are going to be in this house for at least 20 years and even then the return isn't that great. Good for the environment though and if fuel insecurity is going to increase might be a good idea.

Yes, fuel insecurity is becoming more and more an issue. Am hoping to build from scratch next time so can hopefully address that more then...

Reading the newspaper property section yesterday (Times, Friday 8 October) there was mention of solar roof tiles. I wouldn't have panels personally because they are so ugly, but IIRC I think these had a 25 year guarantee and they looked like ordinary rooftiles.

"Solar panels don't even last that long before they need replacing so we didn't go ahead."
We bought 2nd hand PV panels in 1998 that had been used in an experimental installation previously from the late 1980s, they're still happily producing power with no drop-off now in 2021 over 30 years later.
Having said that, it's true that if your only reason to install them is to save money, it's unlikely to be worthwhile.

My dad has a roof of them on his bungalow. I think they were about £10,000.

In the summer, they generate about 2kwh.

The slowest electric car chargers are 3.6kw. And they need about 12 hours. It would take a couple of days to charge your car with solar, more in the winter.

The golden rule with solar PV is to use the electricity when it’s produced. If there are people at home, underfloor heating (electric?), and hybrid car batteries, go for it. Just make sure the electricity is used in some way on bright days. You’ll also be set up nicely for an ev if petrol prices continue to rise.

Payback depends on the electricity rates you pay, and they are only going in one direction atm.

I did some calculations a couple of years ago and it wasn't worth it financially based on 8 or 10 years' usage if I recall correctly. Also, just the aesthetics based on potential resale value of the house.

Our 4kw panels hits a maximum generation of 25 kw per day in early summer. If you can, combine with battery storage. We have had ours for 9 years and KW generated have maintained throughout the period. It should be relatively cheap to put on home office compared to retro fitting to a roof- minimal scaffolding costs etc. I have seen panels flat on the roof - possibly very large roof tiles type- that look much neater than panels fitted on top of the tiles. The finances with no FIT are trickier but the cost of electric has rocketed up so the saving are more - we are paying about 18/19p a unit now but only 11/12p a unit when installed, so the power used saving us now much more, especially if you can either use it during the day or battery store. Winter generation levels can be pitiful, though, so be prepared for that.

We have 12 panels. We were lucky though, they'd been on the house a year when we bought it and we're (and still are) on the highest fit tariff. If we had to buy and pay them off ourselves on the lower tariffs now, we probably wouldn't get them. As it stands, we make back nearly a grand a year.

Home battery storage makes even less financial sense than solar panels at the moment - I definitely wouldn't recommend going down that route!

Electric UFH is a ridiculous idea.

In winter, when you need it, the panels will produce next to nothing.

Energy from electricity currently costs about six times as much as energy from gas.

Electric UFH is a ridiculous idea

Only if you're generating electricity from solar panels, if you've got a windmill it's fine. Obviously that's really only practical for people with enough land and if you've got land you can have ground source heating.

PP mentioned solar tiles, which tesla do as part of their powerwall system. On a new build important to factor in that these will be instead of a roof rather than an additional cost.

FWIW I can only seen issues with electricity supply in the future, and whilst economically solar doesn't make sense at the minute, it'll be a much closer contest in the near future, and the value of having some electricity whilst everyone else is suffering brown outs could be immeasurable. Bear in mind once that starts happening the cost of domestic panels will skyrocket, at least for a while.

A normal PV solar domestic system shuts down in a power cut, so will not help

Thank you. I’ve found this thread very informative.