Solar PV and Battery ... is it worth it?

Freepost

Hi,

I’m posting to enquire about Solar PV and battery storage for a new house that I am building for myself to live in.

I have Solar PV on my current home, installed Nov 2011 and it has proved itself to be beneficial in both reducing power consumption from the grid and also turning a profit on my initial outlay. Whereas, I cannot hope to have a return of the same profit, the FiT scheme has gone, I am interested in reducing costs where possible ….. if it’s possible.

To provide some back ground to my energy usage, in the three years prior to having the solar PV installed, the annual electrical consumption was 4630, 4939 and 4891kWh/pa, say approx. 13.2kwh/day.

Now, for a battery to provide this amount of energy, I have briefly looked at the Tesla Power Wall, which provides 13.7kWh at a cost of approx. £7000 + vat (£8400) and let’s say I install a 4.2kW Solar PV system from Ecocute, on offer at £3795 (I would assume + VAT@5% = £3984). The total cost for Solar PV and Tesla Power Wall = £12.4K ….. that’s a lot of money!

Perhaps the power wall isn’t necessary and a cheaper battery with less storage could supply our needs. Ecocute do a system 8.85kW, made up of 12 x 275W solar panels and a 5kWh battery (I’m not too sure where the 8.85kW comes from) for £7245. With or without VAT included £7245 is still a large chunk of money if I consider, I hope my maths are correct, I consume approx. 5kWh/pa at a cost of 13.65p/kWh = £682.50pa it will take eleven years to break even, this doesn’t seem sensible ….. or am I missing something?

Your thoughts would be most helpful.

Thanks

F.

Solarchaser

At £4k for 4kw, if say you are about right.
A lux hybrid inverter replacing the advertised inverter maybe would cost another £4-500, but you would need to get the inverter model proposed and compare.
Pylon batteries are modular storage of a bit more than 2kw useable for around the £800 mark, so for an extra £3k onto your solar, id expect you to be able to add 6kw of batteries.

How much will it save you.... not easily calculated. 

If we were to assume solar would carry you for say 9 months of the year, the batteries would cover the evening and night, so electricity should be pretty much zero.
But in the 3 months of poor solar, batteries won't charge enough to make a difference....
Unless you move to a time of use tarrif like octopus, and then you could charge your batteries from cheap electric 4-6ppkwh (pence per kilowatt hour seems around right, and use it to offset the expensive times (4pm -7pm) through the batteries.

But you can't mitigate all of your use.
And if your average is 4Mwh a year, even if you *save* 3Mwh, then you are only saving 3000x £0.14 = £420 assuming a 14ppkwh normal electric price. 
At a £7k spend thats a 17 year payback.

You could also earn some more by taking octopus export payments of 5ppkwh, but if you are using 3Mwh of a possible 4Mwh of generation from your solar, there is only a potential £50/year saving from that taking you to a 15 year payback. 

*******
All wooly top of my head calculations,  but I wouldn't imagine they would be too far out.

Hope that helps

Solarchaser

Sorry, should have said, I assumed if building your own house it would be much better insulated than an older house, so I assumed a 15-18% reduction on electricity,  hence going with 4Mwh rather than 5Mwh

Freepost

Thanks Sc, it's a shame that I can't take my existing Solar PV (and FiT of course ) with me.

F.

Solarchaser

Yeah that is a shame, nice FiT is NICE!

BTW I don't know how far you plan on going down the route, but if you had a large enough roof, it may make more sense to cram it with as much solar as you can fit, assuming your inverter could export limit anything above 3.6kw, or you got an agreement from the dno to output more, or...... then the economics from export would get more favourable and perhaps something like ev charging or solar immersion diverter to offset gas usage may be more of a benefit if that was in future plans?

Assuming the £4k for 4kw would become something like £5k for 6kw.

I'm aware that my post was a negative one in terms of roi.
A quick look at my signature would tell you I am not that bothered about roi, I treat it more like a hobby/project, and sometimes it can be more about piece of mind/satisfaction than economics. 

Since the beginning of April I've *bought* 90kwh of electricity at 16ppkwh, or a bit less than £15.
I've used just shy of 1400kwh or £224, so although that's a specific very bright couple of months, and clearly the whole year won't be like that, its really satisfying to be able to still use as much electricity as usual but "save" over £200.

Probably the biggest difference between us is that my annual consumption is around 8000kwh, and I very much feel that solar and especially batteries will work better on a high usage house, because there is more to save.. 

NigeWick

I could afford to be an early adopter so have a solar system, diverter for hot water, Tesla PW2 so I can go off grid if there's a power cut and a BEV.

My view is, If you're not going to be moving for several years and if you can afford it, do it.  An alternative is buying part of a wind farm through https://rippleenergy.com/ as it will save a bit of money on electricity and you can take it with you if you move. Disclaimer:- I have bought shares in the company and will be buying part of their first trial generation as my solar doesn't produce enough to completely power the car as well as the house with battery.

cdunne

I've just spotted this. I'm now likely to purchase a 'PV ME3000 Controller' based system with 3 X 2.4kwh Pylontech US2000 Plus Li-ion battery. Pylontech batteries for £3000 (with the relay so it will maintain the supply to my fridge / freezer in the case of a grid failure).  So with the install it will possibly be approaching the £4000 figure above.

I'm on the last decent FIT tariff (currently Generation: 14.13 p/kWh and Export: 5.5 p/kWh). I believe from asking Octopus I can switch to Prime and keep both parts of this?  The switching to prime also complicates things because I have a plan to be able to dump ~20KW of electricity during a negative pricing period (heaters in a shed with a 40A feed to it).
My existing usage is fairly low but I'm thinking rather than using Gas for cooking change to using electricity via a George Foreman / Microwave, I'm currently working from home so at the moment these are usually ran for free in the middle of the day but when I need to return to work this will be different. 
So basically unless lots of statements about not doing so (and the seller confirms that the ME3000  has WiFi connection,  I'll proceed with it).

Solarchaser

Me3000sp definitely has WiFi inbuilt to it.
I had one until a couple of months ago when I replaced it with a lux.

Imo the lux is a far better system.
If you are buying new (hope so with those prices) then the lux should be the same price as the sofar.
(Reminds me, I need to sell my sofar)

mickyduck55

cdunne said:

I've just spotted this. I'm now likely to purchase a 'PV ME3000 Controller' based system with 3 X 2.4kwh Pylontech US2000 Plus Li-ion battery. Pylontech batteries for £3000 (with the relay so it will maintain the supply to my fridge / freezer in the case of a grid failure).  So with the install it will possibly be approaching the £4000 figure above.

I'm on the last decent FIT tariff (currently Generation: 14.13 p/kWh and Export: 5.5 p/kWh). I believe from asking Octopus I can switch to Prime and keep both parts of this?  The switching to prime also complicates things because I have a plan to be able to dump ~20KW of electricity during a negative pricing period (heaters in a shed with a 40A feed to it).
My existing usage is fairly low but I'm thinking rather than using Gas for cooking change to using electricity via a George Foreman / Microwave, I'm currently working from home so at the moment these are usually ran for free in the middle of the day but when I need to return to work this will be different. 
So basically unless lots of statements about not doing so (and the seller confirms that the ME3000  has WiFi connection,  I'll proceed with it).

Whats going on in the shed to need so much power

joefizz

cdunne said:

My existing usage is fairly low but I'm thinking rather than using Gas for cooking change to using electricity via a George Foreman / Microwave, I'm currently working from home so at the moment these are usually ran for free in the middle of the day but when I need to return to work this will be different. 
So basically unless lots of statements about not doing so (and the seller confirms that the ME3000  has WiFi connection,  I'll proceed with it).

The ME3000 has wifi but its read only - i.e. to get logging data for the app/web monitoring system.

As well as the george foreman dont forget the air fryer, slow cooker and pizza machine ;-)

I dont do it regularly but put 20kwh into the hot tub the other day, first time battery has been down to 20% since march!