Solar panels - how important is the battery?

[thebellagio]

Not an AIBU but posting for traffic

ive been looking into solar panels for my house as I’m terrified of the rising energy prices. Last week I was quoted £11.5k for 24 panels plus the inverter, battery and bird cage around the panels. This seems high and he confirmed that it would take 10+ years to break even.

im currently undecided what to do - that’s such a frickin huge outlay and would basically take all our savings. But on the other hand, I feel like it would reduce our bill and potentially add value to the house which we will be staying in for at least 10-15 years.

I guess what I want to know, is if you have solar panels how essential is it to have the battery as well? I completely get it means in the evening you’re working from the solar power you’ve generated rather than buying from the grid but broken down, the panels are about £6k and the battery is £5k so I’m trying to work out if I could save here…

we use about 6kwh electricity a day according to my smart meter. I’ve been quoted for a 4.2kwh system but a 9.5kwh battery so I’m reluctant to spend that amount of money on a battery if we’re only going to use a minimal amount of the solar power generated. At the moment we don’t have electric cars, so our solar usage is unlikely to change for at least 3-4 years

Has anyone got any advice?

I find the 'return of investment' discussion a bit weird tbh.

what do you want? probably a comfortable house that's easy to sell should you need to, manageable energy bills, climate brownie points.

if you can afford it, go for the most flexible option. your circumstances might change. you or dh might need a cpap snorinator. or develop a medical condition that means you need more heating/more laundry.

That would be the type of thing I would expect someone with lots of money to say.

Others weigh up whether it makes sense because they don’t have massive amounts of spare capital to do their own infrastructure projects unless it genuinely saves them money.

And no - pretty much zero current electric cars have an inverter that allows you to power the house! the Ford F-150 lightning does, and I believe the Hyundai Ioniq 5 can be modified to do so, but neither are widely not yet available.

Please, please - no-one buy an electric car thinking this!

that said - my Tesla does act as a wonderful soak for excess solar energy - but I can’t put that back to the house.

(The ioniq 5 is available but the ones with an inverter are not - and it is unclear whether vehicle to grid will ever be added as a post purchase modification)

Yes my post was aimed at squiggl's neighbour who already have an electric car - Just as something to look into! Same friend is encouraging me to get an EV for the same reason but I'm nowhere near being in the position to get one!

Yep I just thought @SquigglePigs tshouldn’t be misled into thinking that vehicle to grid/home is a widespread thing yet though - it very much isn’t.

And it’ll likely be a while before those cars which can do it are available.

I lived off grid for decades, relying on solar and batteries.

What strikes me from this is that the battery they are proposing seems very small relative to the solar panels, and both the solar panels and the battery seem a lot relative to your usage.

Is the battery lithium? If it is, this means that you will have, on days where you get 4+ hours of sunlight a day, more electricity than you need during the daytime and over 6kwh to use at night (you don't want to discharge the battery to more than about 30-40% on a regular basis, it will shorten its life considerably). If the battery is not lithium then the numbers are different, but the price doesn't make sense, so I am guessing it is.

This system won't really give you the ability to be off grid if you get a number of days of really bad weather (although the panels will still produce even if it's a bit overcast) or in the depths of winter, (for that you would need a much larger battery, though not necessarily a lot more panels) so you will still need your grid connection.

I love having PV and would never want to be without, but if you over-size it it will make the payback much longer.

We've just signed a contract for 16 panels (including solar skirting to stop pigeons getting underneath as I've seen them do it under next doors panels!) and a Tesla powerwall.

The Tesla batteries are expensive, but one of the huge benefits is that Octopus have a special tariff if you have them which only costs 11.5p per kwh for any electricity your draw from the grid. They also pay you the same for drawing power from your battery (they basically take over your battery and use the power from it at peak times, which I think is a great idea).

We're fairly high users, as we have a hot tub (it's been switched off since last September, looking forward to turning it back on).

We did the maths, and figure we'll have a return on our investment in under 6 years, that will obviously reduce if prices continue to go up (we did take the price rise in October into account, but it's now going to be higher than they initially said).

You have to do the maths and work it out for yourself, what will suit one household won't be right for another.

You could only do this if you have a bi directional charger which are quite rare and very expensive. This is because the car battery stores electricity as DC but houses run off AC so you need an inverter to convert it (if I listened to my electrician correctly!!).

We have 10 panels and two batteries, cost £10k in March 22. Battery is brilliant, we use it in the evening to cook, watch tv, use computers, fans on all night, cook breakfast and then it charges up again the following day. We are a household of 4 adults that all wfh. This time of year the solar also powers our hot tub. Best money we have spent, our bill has electricity bill been reduced massively, we were easily using 20 units a day, now we use 20-25 per month on grid. For the first time ever we are in credit with our electricity bill. If you can do it, I would recommend, just check that the installer has suitable accreditation’s.

How much did you spend upfront please Roselilly36 ?

Ah £10K- ignore me!

Ours is eon. £15k on interest free credit for 9kw with 8 kw battery and solar immersion.

We are booked in for solar later this year but the company we are using can’t source enough batteries atm so we will have to wait until next year for that

for us the battery is a no brainier but that’s mostly because we intend to use it to power our electric car

Coming down in price is great. However, what if it doesn’t come down to what the purchaser deems to be a satisfactory price for 5/10 years? In that time, you’ve spent thousands of pounds on electricity whereas you could have spent the money on buying solar panels with the long term view that your electricity will be costing you next to nothing at the end of your payment term. By holding out, you’re only hurting your own pocket.

Martin Lewis did something on solar panels recently on his site if you give it a google

Could you explain what you mean please about the Ioniq 5 and the lack of inverter? I didn’t even know people thought this was a ‘thing’. Thank you! Should there be one in electric cars as we’re getting one next year?

We have 14 panels and a 5.2kw system. We discussed a battery, but the company we were dealing with advised us that the capacity wasn't there yet and they were very expensive. We decided to go for the panels initially as we could always choose to add the battery at a later date when we had lived with the panels for a bit and worked out what our usage looked like.

We did get a water heater, so excess solar power goes into heating our water tank before going back to the grid. We have only had our oil on to heat water for 2 hrs since installation in May. That's a massive saving for us, as previously we would have to have the oil on for an hour a day, even in the summer, to heat water. We have got a lot of bang for our buck out of it. I might be mistaken, but I think you can get the water heater along with a single thermal panel and heat your water that way without the full solar/electric set up.

We are very happy with it. It has taken our energy usage down from 14kw per day to somewhere between 1.5 to 3.5kw.
My DH WFH and I'm P/T, plus we are a family of 7 so there is usually plenty of people in the house during day light hours. It is no problem for us to run the washing machine, oven etc during the day.

Saying all of that, I wouldn't spend your savings on solar panels when your usage is so low. I don't think it's worth it.

I do think the economy is looking dicey and prices are likely to continue to rise. I would be tempted to keep the money in savings and use them to ride this out.

If you have a mortgage have you got a good fixed rate? It's something that might be worth looking at. It could make sense to use some of your savings to pay off a bit of the mortgage and get yourself into a better LTV bracket.

Is your house well insulated?

Are there any big debts you could pay down?

Just some ideas. But as PP have said, with your current energy usage I don't think solar panels is the best use for your savings.

yesterday we received our electricity bill from BG. They want to increase our DD to £135pm for electric and £135 for gas, so £270pm in total. And this is before the October price rise which is terrifying me.

on my previous bill they said estimated usage for electricity over a year would be circa 3500 units. They now say approx 4000 units at an estimated cost of £1,300 per year. not sure how it’s changed but there you go.

so I am seriously still considering it because that’s before the October price rises…

The id4 has bi directional charging. Will collect ours next week

I would be tempted to get several quotes for panels + solar heater. Run that system for a year or two and assess whether you think the battery is worth the outlay at that point.

Sorry if I've missed it, but at what time of the day are you both in the house? Is anyone WFH or part time? Would you be happy leave the dishwasher and washing machine on a timer to start while while you're out at work? Would that invalidate your house insurance?

The id4 software updates for older models will also allow for bi directional. So I presume the same will apoptosis most other brands ie an update on your Tesla will make it compatible in future

the Tesla solar batteries seem the best from what I have seen

There’s 2 adults and 1 child in the house. I work from home so essentially other than the school run I don’t leave the house!!!

Just saw your update. I would definitely go without the battery but with solar heater initially, battery can be added later if you really feel it's necessary. I would get a few other quotes. I'm wondering if you need as many panels as your consumption isn't overly high. Would be interesting to see what other companies suggest.

Good luck.

This is a portmanteau response to several points raised during the thread.

Bird proofing - it’s not to stop them pooing on the panels, it’s to stop them nesting underneath.

Batteries help in two ways:

1. store excess generation during the day to use when the sun don’t shine. With the OP’s figures, if she had a battery she would be paying little more than standing charge from March to September. There will always be some grid draw, because the battery and inverter can’t respond instantaneously. I’m importing less than 0.5kWh per day at the moment, unless I charge the car overnight.

2. Store from the grid on a cheap overnight rate, use it during the day - this is a winter strategy, for when the panels don’t produce as much. Works brilliantly for me, as I have an EV tariff with 4 hours each night at 5p. My day rate is currently 16.26p. The equivalent as a new sign up is 7.5p/40.9p, so I am not looking forward to my fix running out - but OTOH, the savings from overnight charging will be nearly 3 times as much.

My EV tariff is with Octopus, who now insist you have an EV to be on it. Some providers allow you to have an EV tariff without an EV, others have pulled them altogether.

Without an EV, you can still consider Economy 7. That’s also price capped by Ofgem on a different set of figures from the standard variable rate. At the moment, it’s something like 30p day and 21p night, versus 28p for standard variable. So OP could run her house for 21p all winter, and next to nothing all summer. Except (obviously) rates will go up in October.

On getting paid for export - there is a way to get more. Octopus offer 3 export tariffs. The SEG rate is for non-customers and people on their EV tariffs (like me) - 4.1p. For customers on non-EV tariffs - including the standard variable and Economy 7 - you can choose between fixed outgoing at 7.5p, or Agile Outgoing, which varies every 30 minutes on a formula linked to wholesale prices. That is (currently) virtually always more than 7.5p, occasionally ridiculously high (over £1) and latterly averages 18-20p. I wish I could be on it, but giving up my EV tariff would cost me a lot more than I would gain. You need a SMETS 2 smart meter to get paid for export.

My setup - I have an EV which I charge at home, 3.9kWp panels with a 3.6kW GivEnergy hybrid inverter and 5.2kWh battery (4.2kWh usable), installed in December. My usage excluding EV charging is 6-7kWh per day in the summer, anywhere from 8-14kWh per day in the winter. In the first 6 months, my system has cut the electricity bill by 2/3. We have got 50% of our electricity from the panels (32% directly, 18% via the battery), 41% from the grid at off-peak rate and 9% from the grid at peak rate. EV charging is about 40% of our usage overall.

If I were in your position, @thebellagio , I would do two things. I would get the battery, but consider whether a smaller one would suffice. 9.5 sounds suspiciously like a GivEnergy battery size - they are like hens teeth at the moment! But the 5.2kWh one which I have would cost a lot less, but give you the vast majority of the benefits. If it’s another make of battery, there may well be a smaller version available.

Secondly, I would switch to Octopus if you’re not already with them (you can’t do it online, you have to speak to them and explain why you think it would be helpful), go onto their Economy 7 tariff and then get onto Agile Outgoing to get paid for your export. In the summer, you will be coining it from everything you export. In the winter, you save by running the house from E7 night rate.

If you decide not to get the battery, still switch to Octopus and get on Agile Outgoing, but E7 doesn’t make sense then, just go with whatever other tariff takes your fancy.

To register for export with anyone, you need your MCS Certificate and confirmation from the DNO that your installation has been registered/approved by them. Your installer should provide all this paperwork, but they sometimes need chasing to do it.

And finally - using an EV as a battery for the house….. this is possible at the moment ONLY with a car that has a ChaDemo connector (basically a Nissan Leaf or Mitsubishi Outlander PHEV) and a very expensive (like £5K) special bidirectional charger, and as part of a very limited trial. There is work underway to define bidirectional charging standards for the CCS standard, which has become the de facto rapid charging standard for most cars. When that comes, it will also need a special charger, which doesn’t yet exist. There is also work underway to do bidirectional charging via type 2, which is what most home 7kW charger units are. Except that will need new software and possibly new hardware in the car, as well as in the charger. So yes, it will come. But it’s not there yet, and there’s no guarantee that any car or charger you buy today will be capable of doing it.

if you want home storage now, get a battery.