Sanity check - Solar + battery install

Andy0321

Hello and good to be on here.

I've received a quote from EON for a solar + battery system and would like feedback on the proposal. £14,740

Current consumption 2665 kwh per year
Will be charging a car(Tesla long range) once a week going forward

System 4.86kw
Battery 9.5kw

12 x 405w Panels JA Solar Deep Blue
9.5kw battery GivEnergy + matched Inverter
Full install
SEG 15.9p kwh
Battery grid charge (8/9p night rate)

Not sure what other details you would need to advise, except we're based in the North West..

Screwdriva

Welcome Andy! 

A few observations:

1) With your low annual consumption, even with a low usage of a Tesla, you don't need to spend on a battery. I'd suggest skipping it entirely and selling your excess solar to the grid via Octopus Flux instead.

2) The quote you have been offered is ridiculously expensive for 2023. For perspective, here's a quote I've seen just last week:

12 X Sharp 420W Black panels
12 X SolarEdge Optimizers 
  1 X SolarEdge 5kW inverter

£6250 installed. G99 and 20 year warranty on the inverter included. Even if you insisted on an AC coupled GivEnergy All-in-One battery with a far greater 13.5kW of storage, blackout protection and 12 year warranty, it would add another £7K to the total  - ~£13250.

It makes zero sense to go with EON and invest in their kit.  You can do much better!

Andy0321

Thanks for your prompt reply #Screwdriva

I was understanding that I would need to store whatever energy gained throughout the day when not at home for use in the evening and when I did need grid power get it at 8p kwh during the early hours (0200 - 0500).

I may be wrong though and happy to be educated

Screwdriva

Andy0321 said:

Thanks for your prompt reply #Screwdriva

I was understanding that I would need to store whatever energy gained throughout the day when not at home for use in the evening and when I did need grid power get it at 8p kwh during the early hours (0200 - 0500).

I may be wrong though and happy to be educated

That approach makes sense if you want to use only the power you generate yourself for a personal reason, import twice the amount of energy you do, experience blackouts or lack a grid connection.

As your own consumption is so low (like ours), a battery will likely never pay for itself as you will not save nearly enough using this approach. May make more financial sense to invest in as many panels you can fit instead, and sell that excess energy for ~20p per kWh instead. 

Another wise forum member recently posted their thoughts on using the grid as a "battery" so thought I'd share incase you find it useful:

 

Andy0321

A good analogy...
At close to £8k for a battery that last 12-13 years which would cost me approx £51 pm to pay for. In this instance I would never recoup even close to my initial outlay.

Officer_Dibble

I'm glad we got a battery - albeit a much smaller and cheaper one. With Flux I'd hate putting the oven on between 4 and 7pm or doing the washing on cloudy days, even if I knew that we were better off on average. With the battery you don't really have to think at all, just top it up at night - if it's sunny you export for a touch more than you charged for, if it's dull you use it. Top up again from 3 to 4pm if it needs it, to avoid any risk of importing at peak rates, then force discharge during the 4-7 period, leaving enough in the battery to get us through until 2am. All the above is programmed in, it only needs changing if you want to (eg between seasons)

The system as a whole will have a slightly longer payback period than panels alone, but well within the life expectancy of the battery. I suppose we've got a hybrid system with a bit of a battery and a bit of using the grid as a battery.

Andy0321

Officer_Dibble said:

I'm glad we got a battery - albeit a much smaller and cheaper one. With Flux I'd hate putting the oven on between 4 and 7pm or doing the washing on cloudy days, even if I knew that we were better off on average. With the battery you don't really have to think at all, just top it up at night - if it's sunny you export for a touch more than you charged for, if it's dull you use it. Top up again from 3 to 4pm if it needs it, to avoid any risk of importing at peak rates, then force discharge during the 4-7 period, leaving enough in the battery to get us through until 2am. All the above is programmed in, it only needs changing if you want to (eg between seasons)

The system as a whole will have a slightly longer payback period than panels alone, but well within the life expectancy of the battery. I suppose we've got a hybrid system with a bit of a battery and a bit of using the grid as a battery.

Thanks for the differing perspective. I think it'll take some research to get an answer

Netexporter

Security of supply is another consideration, particularly in rural areas, and with the likelihood of winter storms becoming more powerful. With a GivEnergy all-in-one 13.5kWh battery and gateway I could last several days in a power cut, even without any solar input. On the other hand, V2H/G could obviate the need for a separate battery.

Screwdriva

Andy0321 said:

Thanks for the differing perspective. I think it'll take some research to get an answer

https://great-home.co.uk/solar-export-guarantee-seg-calculator/

This calculator may help you with your actual numbers - usage/ system size/ costs etc.

For us (we have a very low annual electricity consumption), using Q4 2023 energy tariffs, a battery would delay the return on our capital investment by ~4.5 years (6.5 years vs. 11.1) 

eyeofthetiger999

It's a very expensive quote.  With your usage you would struggle to get your investment back at all before the invertor or battery would need to be changed.

Qyburn

Andy0321 said:

I've received a quote from EON for a solar + battery system and would like feedback on the proposal. £14,740

Get some other quotes to compare. But be wary of the "shouldn't cost more than .." posts on here, they often bear no resemblance to actual quotes from installers actually prepared to do the work on your premises.