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 didn’t know that! Do you need a special charger, or will any do? How is it controlled? How many kW can it supply?

@PuzzledObserver - I’m not sure the exact details. We were supposed to get 2021 model, but it was delayed so long we have been upgraded.
But we have electrician coming soon and he’s already ordered charger and cables to enable it. I think any charger works and you just need an additional bi direct cable added

@PuzzledObserver that's a brilliant tariff you are on for now.

Would you mind sharing roughly how much you think you save per month? I'm on economy 10 so the off-peak charging option appeals. In Scotland I can get an interest free loan from the government so weighing up if the repayments on this would be worth it.
I might not make anything but I'd have the technology at the end of it and would be less at the mercy of changing prices.

A rough monthly reduction figure would be very useful

@Calmdown14 - yes, it is a brilliant tariff. I have it until November, but am contemplating moving early, as that would fix my rates for another 12 months from when I do it. It would pretty much double my bill…. but avoid the next wave of increases, which I rather suspect may come before November.

Over the first 6 months I’ve saved £244 total, so an average of nearly £41 per month. Here’s my first 6 months of data, for context. I’ve ringed the £ savings line in red. On the Go tariff now on offer, all the amounts would be approximately double.

the “Costs no solar” line is what the bill would be if I used the same amount but didn’t have the solar and battery. I’ve assumed 35% of import is off peak, which is roughly what I used to achieve before the system went in.

SEG = Smart Export Guarantee - the payments I get for what is exported. I’ve deducted that from the bill, so it forms part of the savings.

Also for context - the system cost £8,140 to install.

@Calmdown14 Sorry, I meant to say - for the whole of this year I expect savings of about £600, and more like £1,000 - £1,200 next year because of the increase in prices.

Plus, driving an EV I never visit a petrol pump. My household electricity bill covers pretty much all my driving.

@PuzzledObserver that is massively helpful. Thank you.

I need to make savings of about £80 a month for it to cost nothing. We are all electric so that will be less than half my bill once things go up. And it won't be my own money tied up in it.

Now I just have to find an installer!

So interestingly I’ve been messaging the company about the quote and it’s interesting how different the prices are

for 14 panels but a 7.2kwh battery (not a 9.6 battery) it’s £10.5k (£1000 cheaper than originally quores

hes admitted to me that he’s suggested 14 panels because that’s what my roof fits and says that it would generate more than we need. So I’ve asked for a quote for 10 panels, with a smaller battery and it’s come in at £8.5k for 10 panels and a 4.2 battery - a huge difference from the initial £11.5k!

so my question now, is what would you all recommend?

more panels with a smaller battery? Fewer panels with the largest battery? Or go for a compromise - 12 panels and a 7.2 mid size battery?

for those who have batteries, how long do they last on a singular charge? I know that’s a bit of a pie in the sky question as it depends on how many things are turned on…but there’s only 2 adults and 1 child in the house

What is your annual usage in kWh? There isn’t much point in generating 6000kwh if you only use 2000. That has to be your key question.

if you use say 3000 kWh then at least a third of this will be during months when the solar panels won’t produce much so that takes down your self consumption to 2000. The panels aren’t 100 percent efficient and so if you wanted to generate and use 2000 your panels would need to be capable of generating more than this.

a solar immersion unit is likely to be a better option than feeding power into the grid for which you will only get about 4p a unit so add that into your calculations.

It looks from your opening post that you only use about 2000kwh for the entire year. That means you’ll only be self using about 1300kwh, anything else you’re basically gifting to your energy company. On that basis you don’t need a 4.5kw system since won’t that produce about 200 percent more than you need?

what are the figures they’ve quoted you?

My previous bill had suggested an estimated 3500 kWh per year. The bill that arrived on Friday from British Gas said they estimate 4050 kWh per year.

my smart meter says that we are between 6-9kwh per day on average

They say that 14 panels would generate 4593 units via solar production and 10 panels would generate 3281 units via solar production.

We don't have a battery. But we are on an older feed in tariff so its quite lucrative for us. You do learn to change your habits to make the most. Staggering appliances and literally making hay whilst the sun shines.

We are looking to change as many of our heating options from gas to electric as a result to make the most.

Had our Tesla Powerwall (battery) fitted just before Storm Arwen hit. It kept us going through the 32 hours of power outage. We charge the battery from solar power (the ideal scenario) when possible and carry on running off stored solar into the evening and overnight. We also charge up on very dull days and in winter from the grid using the cheap rate electricity we get overnight on our electric vehicle tariff - 7.5p per KWh from 00:30 to 04:30 - and can then run off that during the day if the solar is not producing enough. Yes, our day time tariff is 30p per KWh - but we very rarely use any power at that rate. Combined with the fact that we run our electric car mostly off solar power (occasionally need to charge at cheap rate overnight) I think our payback time won't be too long. Last week we used 46p worth of electricity plus £1.75 standing charge, but minus however much we uploaded back to the grid - payed at only 3p per KWh so we don't tend to worry much about that.

The rule of thumb in solar circles is to put as many panels onto the roof as you can fit. There are fixed costs in the install (scaffolding, running cables, installing the inverter, having people on site) which are the same whether you have 10 panels or 14, so the extra is not much more than the actual cost of the 4 extra panels.

Panels are a long term investment with a 25-30 year life, and it’s quite likely that your usage will increase in the future. It might be an EV, or a heat pump…. or an air conditioner!! Meanwhile, you can sell your excess back to the grid for a lot more than the 3-5p most suppliers pay, by switching your supply to Octopus and then getting on Agile Outgoing for your export. PM me if you want a referral code which would give both of us £50 credit!

So on balance I would say go for the 14 panels. If you don’t want to spend all your savings, go for the smaller battery, it will still add to your savings, and you still have the possibility of charging it cheap over winter if you take an Economy 7 import. You will be glad of the extra panels in the winter when is a lot lower. You can always add more battery later.

If you use just over 4000 throughout the entire year then you won’t use everything you generate with the 14 panel 4500 system. That’s because even though the usage and generation numbers look fairly close, the reality is that not much will be generated in Winter and so you’ll still be importing energy from the grid.

puzzled makes a good point about peoples usage increasing though. If it’s normal to max out the roof space then if you can afford it will be cheaper than trying to add more later

Have you not considered the Tesla Powerwall tariff with Octopus? Costs around 11.5p per kwh at any time.

Just wondered if you'd considered it then discounted it, and if so why? It's what we're hoping to do once ours has been fitted later this year.

Thought about it, yes, but discounted it as it would mean we would need to allow Octopus to pull power from our Powerwall when they need to. We felt that we were better off using as much as possible of the stored energy ourselves and thus avoiding paying the day rate, 30p per kWh, rather than gaining the Tesla feed in rate. We have both an electric car and an electric motor bike so it's not that often that everything is fully charged and we end up feeding to the grid! At the moment the car is charging up so nothing going to grid.

Get another couple of quotes.

Panels. Not batteries.

We got solar panels in March. So far working well. We didn't get a battery because of the cost and the lifespan of the battery. We wouldn't recover the cost of the battery in its lifetime so its pointless. We are minded to perhaps invest in a battery in a few years time, as we think the technology is moving fast and that will also drive the cost of them down.

Dh was reading yesterday that suddenly solar panels are being seen as attractive to house buyers. Previously they didn't make much difference to the price of a house but with bills rising fast thats changing. The thinking is now that it adds £10k to the value of your house because people don't want the hassle of arranging it themselves.

Thats what I'm thinking, that the ROI on the panels is going to become a value-add for properties.

Do you regret not having a battery at all?

My thinking at the moment is that it's a bit of a gamble with the new government coming in. I think the likelihood of them announcing new measures is actually fair high and I don't want to pay over the odds now, only for the govrnment to announce something in the next few months

No regrets yet. We are managing how we use electricity. Yes its summer but we are getting a fair amount more electricity than we need the majority of the time. Ask me again in the winter!

We bought literally just before they made a change in the VAT. It was a difference of about £350.

My thought is that you are taking a gamble on waiting. Yes you might get some subsidy for installing from government but with demand for solar panels rising (probably quicker than can be installed) and inflation being so high, I think waiting to see if there might be new green incentives is probably not going to be worth it.

I think rising prices on electricity will, in itself, push people over to solar if they are in any sort of position to afford it.

The cost of living crisis will also make it difficult to justify lots of subsidy going to richer middle class homes with savings rather than helping those on lower incomes with bills. Especially if the installers do hit a problem with matching demand, which I suspect will happen soon enough.

I could be completely wrong of course, but its a gamble either way.

We bought just after the vat change but our quote was pre vat change. The quote was adjusted for the new prices. The vat came off but the price of the system jumped up to compensate because demand spiked!

@User952539 I luckily agreed my quote prior to the VAT change but then didn't pay the VAT because of the change so got a very good deal. The company I am dealing with have stopped taking orders as they are booked up for the next year at least!

If I used the same amount of electricity as you, I wouldn’t bother. If you are going to, I would definitely get more quotes. We’ve been quoted for a 10KWh system with 9.5KWh battery and it’s not that far off what you’ve been quoted.