Home Battery with Solar

Cameron1590_2

Hello,

we are looking at getting solar panels fitted and had a few quotes from various local and national installers. 

Many of whom had a default position of having a battery fitted at the same time. I’ve been crunching various numbers and think we’d actually get a quicker return on our investment without a battery. 

This is primarily due to our already low usage. 

Current price per KWh £0.22p
Export rate per KWh £0.15p

Two adults at home all day/night. We use approx. 2,400kwh a year (according to electric bill). 

12 panels - 5.2kw system split east to west. 

£6k 

12 panels - 5.2kw (as above) with 9.5kw giv energy battery is £9.9k 

based on my calculations, payback is around is much quicker without the battery. With the battery, payback is around 14/15years by which time the 12 year warranty will be up and it may, or may not still work/hold a decent charge. 

Am I missing something obvious? 

Thanks

Netexporter

Do you have a smart meter? That could make a lot of difference to the calculations. You could import at lower than the export price, for example, so the battery could make money in winter, even if there is little solar input.

badmemory

You are missing a trick with the battery though as you can fill it at cheap rates & use when needed.  Bearing in mind that I have had my best day for a few weeks & actually only yielded 4kwh.  Back in August it was nearer 40 kwh.  My installer told me that they would not do installations without batteries or people wouldn't reach the normal payback of at most 10 years.  I have worked mine out to expect 8 years & that is with a fairly small roof & high usage for the house size.

Cameron1590_2

Thanks, that is helpful. I hadn’t thought about low solar output in winter. So essentially I could top the battery up on a cheap overnight tariff (say 8p a unit) and use that to get me through the day vs paying the 22p a unit. 

badmemory

I have had a couple of days when the yield was not even 1 kwh.  The sun when it is up is also very low in the sky which does not help.

And also exporting even more in the daytime in summer as your battery could remain full for longer.

Nick_Dr1

Battery prices are falling. For example, check out Fogstar batteries. The case for batteries is improving by the day as battery prices fall and smart tariffs allow load shifting. The balance will change the other way though if electricity prices fall. Difficult to predict over 8 years though!

Netexporter

Also. don't worry about the warranty. Hammer the battery, to get your ROI as soon as possible. Batteries will be cheaper and better before you break the one you've got now.

badmemory

I thought getting solar was a gamble worth taking & anyway new learning curves when pushing 80 are a good idea.  I won't be getting an EV though unless they make a very much smaller model or I magic up a much larger garage.

Netexporter

There's a rash of small EVs coming on the market at the moment, mostly with pretty decent range. 

So far I've got EV, heat pump and solar plus a share in a windfarm. Just have to live to 95 to get the full benefit of the latter! Batteries, with islanding, this coming year and then I'm all set for the Apocalypse.

Screwdriva

Cameron1590_2 said:

Two adults at home all day/night. We use approx. 2,400kwh a year (according to electric bill). 

12 panels - 5.2kw system split east to west. 

£6k 

12 panels - 5.2kw (as above) with 9.5kw giv energy battery is £9.9k 

The comments on this thread are a decent representation of the variety of opinions that exist out there. However, when you look at the numbers, it is clear that your current import of 2.4mWh is too low to justify the cost of a battery, no matter how you slice it. Your calculations/ instinct are directionally correct. 

It would be wiser to invest in the maximum # of panels that will fit your roof, export your excess Solar PV to the grid and invest the £4K+ towards a better, cheaper battery down the road, when a heat pump and/ or EV become part of the household.

For perspective, installers I use offer:

12 X Sharp 435W Bifacial panels (25/30 year guarantee) +
12 X SolarEdge optimizers +
  1 X SolarEdge 5kW inverter (20 year warranty) for £5.75K 

10 year workmanship warranty, G99 and bird netting included. Bifacial panels tend to outperform on E/W aspects in UK conditions with a white roof background, which the right installers should include as part of the installation. 

Take your time finding the right installer for your job. It's a buyer's market out there! 

SuzeQStan

Netexporter said:

There's a rash of small EVs coming on the market at the moment, mostly with pretty decent range. 

So far I've got EV, heat pump and solar plus a share in a windfarm. Just have to live to 95 to get the full benefit of the latter! Batteries, with islanding, this coming year and then I'm all set for the Apocalypse.

How will you prevent potential electrocutions islanding?