Sunplug Solar Battery

Pricy147

Had mail from EDF advertising a Solar backup battery 3.3kw with inverter. £4k including VAT and installation!!!!!


I do not see how this can possibly be viable? A 4kw PV installation may generate 3000-4000 KW per annum. Maximum battery storage is 3.3kw - even if (in winter months!) we could charge it fully EVERY day - then it would hold 3.3*365 = 1200kw per year. If you used the full 3.3kw every evening - saving aroun 15p per kw - then that's a saving of £180 pa.


It would take 22 years just to get your money back - excluding the fact your original money would get compound interest if left in the bank.


So even with unrealistic figures - it no way pays!


I haven't phoned for a quote - am I missing something here!? Anyone looked into it in more detail?


3.3kw seem way to small for a start - would think atleast a 10kw would be necessary.


Only upside I can see is less reliance on grid - which for a marine fish keeper is tempting in case of power failure.

PaschalFun

Pricy147 wrote: »

Had mail from EDF advertising a Solar backup battery 3.3kw with inverter. £4k including VAT and installation!!!!!


I do not see how this can possibly be viable? A 4kw PV installation may generate 3000-4000 KW per annum. Maximum battery storage is 3.3kw - even if (in winter months!) we could charge it fully EVERY day - then it would hold 3.3*365 = 1200kw per year. If you used the full 3.3kw every evening - saving aroun 15p per kw - then that's a saving of £180 pa.


It would take 22 years just to get your money back - excluding the fact your original money would get compound interest if left in the bank.


So even with unrealistic figures - it no way pays!


I haven't phoned for a quote - am I missing something here!? Anyone looked into it in more detail?


3.3kw seem way to small for a start - would think atleast a 10kw would be necessary.


Only upside I can see is less reliance on grid - which for a marine fish keeper is tempting in case of power failure.

A few things to consider.

First off, the batterey is "Designed to enable homeowners to become more energy independent, Sunplug reduces your reliance on the National Grid and maximises use of clean, renewable solar energy."

So it's probably not going to be totally cost effective. It's more about saving the planet. e.g. compare the cost of an electric or hybrid powered car to a traditional petrol engined one.

Secondly, you only appear to allow one charge/recharge per day. But it may recahrge several times depending on your load.i.e. if you are attempting to draw more energy at a given time than your PV can provide, then the battery can supplement it.
In contrast. it is "not suitable for back-up or off-grid system"

Thirdly, do shop around.
I haven't looked to hard, but the first alternative source I found was charging only about £2.6k for the same battery which includes VAT but excludes installation. That's retail price, and it indicates a discount for trade is avalable. It also suggests "Simple installation process - takes 5 minutes!"
So whilst a qualified electrican should be used, I can't see the installation costing £1.4k

There is a 8.8kWh battery also available for about £5.4k inc VAT, but I'm not sure if it's compatible with the small inverter you describe.

Pricy147

Interesting feedback, and hadn't thought of the in-day re-charge cycles perhaps on cloudy days, etc. On the other hand my calculations were unrealistically optimistic given some winter days you generate no, or very little power - so probably averages out.


I think the technology probably has a long way to go to justify from a cost/benefit perspective - unless you goal is purely environmental, or de-risking some critical item like a fish tank, etc.

Andy_WSM

Pricy147 wrote: »

or de-risking some critical item like a fish tank, etc.

I'm not entirely sure these battery units will do that! I think they need to be grid connected to work - in the same way your solar system does, If you get a power cut your PV stops generating. A large UPS is the way forward for critical marine equipment - which could in turn be plugged in to a PV battery system.

None of this is going to save you any money though!

Cardew

Pricy147 wrote: »

or de-risking some critical item like a fish tank, etc.

A small portable generator costing around £200 would be a better bet.

rtho782

£5k will get you a tesla powerwall 2 which is like 18kWh, why would anyone buy this...

It can actually make sense even without solar. Two of those and I could comfortably run my whole house on economy 7 24 hours a day, charging overnight.

That alone would reduce my unit rate from 8.4p/kWh to 4.2p/kWh, in effect.

Cardew

rtho782 wrote: »

£5k will get you a tesla powerwall 2 which is like 18kWh, why would anyone buy this...

It can actually make sense even without solar. Two of those and I could comfortably run my whole house on economy 7 24 hours a day, charging overnight.

That alone would reduce my unit rate from 8.4p/kWh to 4.2p/kWh, in effect.

If I understand you correctly you could save up to 36kWh a day if you fully charged and then fully discharged the batteries each day; saving 36 x 4.2p a day.

How would you use 36kWh every day in the summer?

That would mean a saving of £1.51 a day, £551 a year. So leaving out the fitting and associated equipment, it would take 19 years* just to pay the £10k for the batteries, even if they would survive 7,000 charge/discharge cycles.

* I appreciate electricity prices will increase, but £10k invested long term at only 2% would produce £200pa compounded.

Doesn't seem like financial sense to me!