Solar battery - are they worth it now?

lisyloo

Just have a quote £4k for 3.2kw battery.
10 year warranty with ese group.
have 12 panels 3.9kw system with solar edge.
annual consumption 7,300 units 
5 bed house with hot tub 
I don’t think we can tell how much of the solar we’re using.

I appreciate it’s impossible to be exact but anyone got a rough guide as to whether this would be a worthwhile investment?

pcgtron

You use 20kw per day averaged out over the year. A 3.2kw battery is not going to touch the sides. 4k for 3.2kw is also very expensive. I paid about 5.5k for 13kw, although that was the same time as a solar install, so no vat 

EcoScruples

£500 per Kw for a battery should give you an idea of value, Pylonyech are mentioned a lot on the boards and seem to offer great value right now.

Get yourself on a decent export tariff and save you money.

powerful_Rogue

Very expensive for a battery.

On average we use 10kw per day and have 13kw battery (11.7kw after you deduct the 10% buffer) and thats just enough 95% of the time.

JKenH

Over 10 years a 3.2 kWh battery has the potential to store 9344 kWh (after allowance for cycling losses). In summer can you use 3.2 kWh of stored energy on top of what your panels are covering? Dull days you probably will but sunny days probably not. In winter have you enough spare solar PV to fill your battery - probably not? Batteries are at their most useful in spring and autumn. 

For the purposes of working out payback, assume you might actually be able to use 5000kWh over the 10 years. That will be costing you 80p/kWh over 10 years or 40p/kWh if your battery lasts 20 years. 

As suggested by @EcoScruples have a look at a tariff like Octopus Flux. You will be paid for your export of surplus solar PV at around 22p/kWh. On a good day in summer when perhaps you might have around 20kWh of surplus PV which could earn you £4.40. You can then use that £4.40 to buy back electric from the grid when you need it at around 32p/kWh (approximately 14kWh). Look at it as putting 20kWh into a virtual battery and getting back 14kWh. (That’s efficiency of close to 70% compared to a physical battery at say 80%).

The beauty of it is over 50 decent summer days you could put 1000 kWh into your virtual battery and in winter get back 700 kWh without any capital outlay. What real battery could give you that?

markin

Are you on deemed FIT?

Maybe simpler to install a separate small solar system, do you have roof space?

Screwdriva

JKenH said:

The beauty of it is over 50 decent summer days you could put 1000 kWh into your virtual battery and in winter get back 700 kWh without any capital outlay. What real battery could give you that?

Incredibly well articulated! Totally agree! Octopus Flux is a game changer!

I'd only add that there are massive environmental benefits to feeding excess PV to the grid during peak solar generation months, when wind energy is nearly non-existent and the only alternative is burning gas.

And, depending on your geopolitical and ethical views, you're not funding the manufacturers of the batteries either.

lisyloo

markin said:

Are you on deemed FIT?

Maybe simpler to install a separate small solar system, do you have roof space?

Yes 50%.
no, all viable roof space (SE & SW facing) is covered with 12 panels

EcoScruples

Screwdriva said:

JKenH said:

The beauty of it is over 50 decent summer days you could put 1000 kWh into your virtual battery and in winter get back 700 kWh without any capital outlay. What real battery could give you that?

Incredibly well articulated! Totally agree! Octopus Flux is a game changer!

Very well put indeed, hindsight is a wonderful thing they say and how true in this case, when I bought my battery, electric prices were heading for 60p per kw and the payback on a battery was down to about 6 years for me.
Had I known then what I know now I'd have saved my cash.
Payback should still be under 10 years but hey ho, you win some you lose some.
I just have to think of ways to make my investment work harder for the return.

Reed_Richards

Screwdriva said:
Incredibly well articulated! Totally agree! Octopus Flux is a game changer!

But can you rely on it continuing?  Or continuing with the same good rates?  What would really be a game changer is if other electricity companies followed suit and brought out their own similar tariffs.  As things stand, relying on the continued existence of Octopus Flux is very much putting all your eggs in one basket.  

JKenH

Reed_Richards said:

Screwdriva said:
Incredibly well articulated! Totally agree! Octopus Flux is a game changer!

But can you rely on it continuing?  Or continuing with the same good rates?  What would really be a game changer is if other electricity companies followed suit and brought out their own similar tariffs.  As things stand, relying on the continued existence of Octopus Flux is very much putting all your eggs in one basket.  

No you can’t predict what tariffs will be available or what electricity will cost in the future but for now Octopus Flux is a cheaper/more cost effective option for storing one’s own generation particularly if you have a big solar array. If Flux disappears next year then you can revisit the idea of batteries again at that stage. Perhaps they will be cheaper then.