Is solar battery storage worth it?

nologo

MouldyOldDough said:

Exactly how safe are Solar Batteries - assume Lithium ?

You do hear increasing numbers of reports of fires caused by lithium batteries. If your solar battery goes up - then it's goodbye house and possibly life !!

I'm sure there is only 1 case of a Bess catching fire, has anyone else have a documented case?
thats not a cheap ebike using the wrong charger. 
regards..nologo

OctoCat31

Thanks so much for this guide it’s really useful.

Would it be possible to add something in about whether it’s worthwhile to move to battery storage now (or before the VAT applies) if you are still receiving payments under the old Geed In Tariff scheme please? As I know this is more generous than the current SEG scheme.

Thanks

astroL

We had a 1.8kW solar panel installed ~10 years ago and then supplemented it with a total of 6.4kWh batteries almost two years ago.  My original figures for cost/benefit were based on the assumption of 100% (or near) efficiency and I did not know about controllers not being 100%.  The figures were thrown to the wolves within a week or so of the system being put into operation.  Yes, during much of the year the pv contributes a lot to the batteries; otherwise I have the system set up to charge overnight during the cheap rate.  The figures would be fine but switching on a power drain - eg., a 2kW kettle (or of course anything else) does not result in a switch to battery power in seconds.  There is a *minimum* period of the fast-asleep controller waking up to see the power drain and then slowly switching it over in stages.  A complete switch can take a minute or more - not just 10 seconds as claimed by the manufacturers :-(   So the net result is that we still continue to take power during peak rate for much longer than I originally expected.  This destroys the economics.  Other systems may work better.  I strongly suggest that you do some serious investigations before 'investing' in storage batteries.  The controller is a very weak link.

AndyB

Please edit this again. Solar Batteries? Solar Panel Batteries? It's just Battery Storage. You don't need Solar to have battery storage at home, and this article needs clarification to avoid further confusing your readers.

The headline would read better: "Is home battery storage worth it?" 

BitOfaNerd

I wouldn't get solar panels installed without a battery to maximise their usefulness.  The amount of energy generated every day varies hugely from 0.5 kWh (rainy day in Dec - Glasgow) to 30 kWh (sunny day in June).  In the summer we are usually generating more than we can use at one time so without a battery this would be fed into the grid and then as soon as you turn on the kettle and have the oven on at the same time etc.  you're drawing from the grid at a much higher price.  Our 3.6 kW solar panels plus 2.7 kW battery prevents this almost all of the time.
 I have an electric car and I'm signed up to the Octopus Go tariff which also allows us to charge up the 10 kWh battery overnight at the cheap rate.  In the last 12 months we have saved approximately £1600 on our electricity bill roughly evenly split between the solar panels/battery and moving most of our energy usage to the cheap overnight rate (we also have a hybrid air-source heat pump so our electricity usage is high) .  I vary the extent we charge the battery overnight from fully in the winter to not at all in the summer.

Some nerdy figures for anyone interested.....  
3.6 kW solar panels (as limited by DNO) and 10 kWh, 2.7 kW battery, living in Glasgow

Dec:
Generated 39 kWh with solar panels.  Total electricity usage: 5% solar, 75% at cheap overnight rate, 20% at peak rate.

June:
Generated 570 kWh.  Total usage: 88% solar, 8% cheap rate, 4% peak rate.  Fed in to grid: 51 kWh (we also have an Eddi and I charge the car during the day with the slow charger on sunny days to minimise feed in).

Our biggest savings were in March (no idea why!) with approximately £70 saved with the solar panels and £115 with Octopus Go compared with a standard tariff (this figure also includes charging my car at night not just the battery).

greenmeany

Having just read the article about batteries and solar power I would like to see a reference relating to those of us on the old Feed in Tariff having had Solar Panels for around 12 years now. We got in under the line when the government decided the scheme was too generous and was dealt with by the European Courts! Never been so lucky in my life.
My panels have paid themselves off and raised a further £5.5k in profit....yes,  and I get a "deemed" payment of 0.0482p per kWh from assumed use  and 0.6830p per kWh for generated energy back to the grid.  Anyone in my position would be bonkers to even consider buying a battery and should be warned...there be sharks....

NedS

BitOfaNerd said:

I wouldn't get solar panels installed without a battery to maximise their usefulness. 

I'm not convinced. I may have previously agreed with you when SEG payments were really low (4p), but now SEG payments of 15p are available against an import cap of 22p the financial benefit is much reduced.

Assuming you have solar, excess solar can be exported for a SEG of 15p to the grid at no cost (think of this as a large free battery). Current Ofgem cap is around 22p, which constitutes a 7p margin (or cost) per kWh to store your excess solar for free and use it again later. Storing energy in a battery and taking it back out again is inefficient (not 100% efficient), so that 7p margin will be reduced, to maybe 6p.

How many kWh at a 6p margin will you have to store and later use to cover the cost of a £3500 5kWh battery installation with a usable life expectancy of 10 years? £350/year = 5,800kWh per year cycled through your battery, which means you'd need to cycle 16kWh/day to break even through your 5kWh battery. Not going to happen.

Now maybe you can improve the margins by charging the battery at cheap import rates and then exporting or using at peak times, but again I'm still not convinced the numbers stack up. At best, you may be able to cover the costs of the battery in the 10 year life of the battery.

IMHO a better (and simpler) financial solution is to fill your roof with as many solar panels (with a 25 year lifespan) as possible and export as much as possible at 15p SEG to offset annual usage. A battery simply adds to the costs and diminishes returns. I'd spend the cost of the battery on more solar panels and a larger inverter, and stick the rest in the bank at 5% as it will give a better financial return than adding a battery based on today's prices and rates.

Dolcetta

The old Lithium batteries were more susceptible to fire risk, but the new Lithium ion phosphate batteries are not. Also most things electrical including solar systems work better in COOLER temperatures! 

greenbee

I have my battery primarily as backup in case of power outages as I work from home. We'll probably never have another one again now, but it's worth it for that alone. It's connected to the circuit that runs my office, so my laptop and internet connection can still be used - and given how little power they draw, I'll have no excuse for not carrying on working even if we're cut off for quite some time!

ed110220

MouldyOldDough said:

Exactly how safe are Solar Batteries - assume Lithium ?

You do hear increasing numbers of reports of fires caused by lithium batteries. If your solar battery goes up - then it's goodbye house and possibly life !!

Most (all?) current domestic batteries are LiFePO4 (lithium iron phosphate) which is not flammable, unlike lithium-ion. Having said that, the risk from Li-ion has been sensationalised recently. Some of it is just the novelty of the new or unusual - an EV fire is newsworthy in the way a much more common petrol/diesel car fire isn't just as, say, someone being killed by a shark is newsworthy but someone dying from an allergic reaction to a bee sting isn't. Some is just culture war nonsense where you look at the other things being pushed and it's things like "climate change is a hoax", "Enoch Powell was right" etc.