Help with panel quote?

Planeteer

Unfortunately I am not very technical and I am generally very suspicious of installers, but I am a passionate energy saver, both for the planet and the wallet. So would like to get a sense check of this solar quote from a company called Rest.

First my context: 4 bedroom detached house in London, being offered 8x 375 panels (Eurener from Spain) with a 3.3 kw battery from Growatt, for an East facing roof (35° roof, 90° from true south, no shading) for £11,850 (gulp).

My own electricity consumption is c. 1000 kWh annually (or £400 on Octopus Tracker), and my hope is to have some energy autonomy and economy, with a lower carbon impact as a bonus.

They've done some ROI projections for savings based on current prices (+7% API) over 30 years suggest 13.5% ROI against not doing anything - not sure how much merit to give it.

Is solar a good idea, even for a lower consumption? Or is waiting  better idea - if the government might offer any subsidies?

All thoughts most welcome 🙏 

Screwdriva

A few thoughts:

1. The government is unlikely to offer any subsidies on solar going forward. Isn't hard to see why after the FIT tariff cost the taxpayer so much and the ROI on a rooftop system can be as low as 5 years.

2. With such low consumption annually, a battery makes zero sense. Try this calculator out to see an estimate of your payback.

3. If you have a detached house, do you not have a West or South roof aspect? With an East only aspect, you won't really benefit from a full days generation, which will only delay your return on investment further. 

4. The quote is obscenely overpriced. Your cost should be < £ 5.3K for 8X Sharp 400W panels, SolarEdge inverter and optimizers, all with a 25 year warranty.  

If I were you, I'd tell those installers to give it a rest! 

5. You would be exporting >90% of your PV generation via Octopus Agile's variable SEG tariff to maximize your return. The calculator above should estimate this well. 

DougMLancs

The quote seems very high, even for London. What configuration is your roof- Just 8 panels and just on the east side doesn’t seem to be making the most of a 4 bed detached house. I can’t find Rest Systems on the MCS register even though they’ve mentioned MCS registration on their quote. Is there any other name they have they might have registered under? if they’re not MCS registered I wouldn’t go near them with the proverbial bargepole. 

ABrass

Batteries need you to be using the power they store. With an average daily use of 2.75kWh it'll never pay for itself.

rew81

Agree with the above comments, your quote is overpriced. What is your electricity usage pattern? 

Planeteer

Thank you all - my going in estimate was also half the quote, but I don't know whether prices have increased. 

Not sure how to answer usage pattern - low general use, some evening TV/cooking, some daytime WFH, rest on gas combi boiler. No EV//dryer. 

Roof ridge is N-S, so only gable faces south. Westside faces a park, so may provide shading.

I'm with Octopus so thought of exporting surplus - for which I thought I needed a battery. Guess that's not needed for exporting then?

Interestingly, the installer also recommended not joining National Grid's Social Energy programme, and spoke of Eurener panels being equipped against solar spots. Hogwash, too?

Will try calculator next! 

DougMLancs

Planeteer said:

Interestingly, the installer also recommended not joining National Grid's Social Energy programme, and spoke of Eurener panels being equipped against solar spots. Hogwash, too?

If he meant the Smart Export Guarantee (SEG) (can’t think what else he meant) then that’s because if he’s not MCS registered then you can’t claim SEG and no, no battery needed to export.

How close are any trees on the west side? Have a look at how much shading that side gets through the day. It might still be worth exploring panels there with optimisers/micro inverters if needed.

QrizB

Planeteer said:

They've done some ROI projections for savings based on current prices (+7% API) over 30 years suggest 13.5% ROI against not doing anything - not sure how much merit to give it.

As well as all the other feedback you've received, that ROI calculation is voodoo economics. Electricity prices are currently at an all-time high and suggesting they will continue to increase by 7% above inflation for 30 years is bonkers.

If electricity is today 34p/kWh, that would mean a price of 260p/kWh *in today's money* in 30 years' time.

If electricity does ever reach a year-long average of 260p/kWh, payback time for grid-scale solar will be measured in weeks not years. One good summer would do it.

Planeteer

DougMLancs said:

Planeteer said:

Interestingly, the installer also recommended not joining National Grid's Social Energy programme, and spoke of Eurener panels being equipped against solar spots. Hogwash, too?

If he meant the Smart Export Guarantee (SEG) (can’t think what else he meant) then that’s because if he’s not MCS registered then you can’t claim SEG and no, no battery needed to export.

How close are any trees on the west side? Have a look at how much shading that side gets through the day. It might still be worth exploring panels there with optimisers/micro inverters if needed.

He didn't mean SEG, but Social Energy who seem to offer you money for access to your battery, and whose reviews are pretty bad (https://uk.trustpilot.com/review/social.energy), so that doesn't make any sense.

I will now obtain some alternative quotes from suppliers kindly suggested by the commentators above - so let's see what those come back with.

Thank you in the meanwhile for the warnings!