Solar + battery quote check please – 6.8 kWp + 10 kWh battery for £7.3k net, good deal?

tunatuna

Hi all,

I’d really appreciate a sense-check on a solar + battery quote I’ve received before I pull the trigger.

System details

• 15 × 455 W panels = 6.83 kWp
• Hybrid inverter: Solis S5-EH1P5K-L (5 kW)
• Battery: Dyness Powerbox G2 – 10.24 kWh (about 9.7 kWh usable)
• MCS certified install including scaffolding, bird protection, commissioning etc.
• Panels split across two good roof planes (SE and SSW-ish), no shading, normal roof pitch.

Installer estimates ~5,900 kWh/year generation, which seems plausible for Derby with these orientations.

Price

• Total quote: £8,295 installed
• I can claim £1,000 cashback via mortgage, bringing net cost to £7,295.

Usage

• Current electricity consumption about 3,000–3,700 kWh/year, likely closer to 3,000 going forward.
• Work from home, so decent daytime usage.
• No EV yet, but possible in future.

Plan is to:

• Run house loads + battery from solar
• Export surplus on Octopus Outgoing (~15p/kWh)
• Potentially use immersion heater in summer once battery is full.

Rough maths By my calculations:

• Expected annual benefit around £1,000–£1,100/year
• Simple payback roughly 6.5–7 years

Questions:

1. Does £8.3k installed (or £7.3k net) look competitive for this size PV + 10 kWh battery system?
2. Does the system size look sensible for my usage, or oversized?
3. Any red flags with Solis + Dyness kit?
4. Anything I should double-check before signing?

Really keen to hear real-world experiences or views from anyone with a similar setup.

Thanks in advance!

powerful_Rogue

I've seen better deals. The company I used which was recommended to me by @Screwdriva on here are currently offering:

Get 10x500W bifacial solar panels, a 5kW inverter and 2x15kW batteries for just £9,995 from now until 31st March 2026!

QrizB

OPI think your quote is OK. A year or two ago it would've been crazy cheap, but prices have come down.

Solis inverters are from the value end of the market; I have one and it does what it's meant to do. My near neighbour also has one, coupled to Pylontech batteries and he's happy with his too.

Dyness batteries are mainstream.

You've not mentioned the make or model of your solar panels but they're probably a budget Chinese brand. There's nothing inherently wrong with that, but the quote powerful_Rogue has shared will be Eurener panels; manufactured in Europe and with a better warranty (and less chance of having been assembled by slave labour).

Screwdriva

When it comes to the quote, I would be somewhat concerned by the following:

1. No brand of panels mentioned. This usually translates to bottom of the bargain basement brand from the Far East. Reliability and aftersales can be non-existent.
2. Solis is the inverter equivalent of 1 (Wholesale price of < £650). Also appears undersized for the size dual South aspect array.
3. Dyness is the battery equivalent of 1. (Wholesale price of < £1.5K). Ineligible for the lucrative Intelligent Flux (IOF) tariff

Lack of quality from this installer aside, sounds like your consumption is forecast hover around the ~3 mWh per year mark, which will make it very difficult for a home battery (that's not on the IOF tariff) to pay for itself within the warranty period. For your perspective, the following are on offer from 2 installers I use:

Option 1) If £ is primary factor, I recommend:

15 X Eurener 515W (7.7 kWP) bifacial panels paired to 15 SolarEdge optimizers and 8kW SolarEdge inverter (20 year warranty). < £7K installed.

Option 2) If you can stretch your budget, I recommend

15 X Eurener 515W (7.7 kWP) bifacial panels paired to a Tesla PW3 (13.5kW usable). < 12K installed installed

In both cases, 10 year workmanship warranty is included, which is helpful should a service callout ever be needed.

Well done on getting some £ back from Halifax! You can do much better when it comes to an installer offering, Hope this helps!

tunatuna

Thanks for the replies, this has given me some food for thought.

Panels quoted are DMEGC 455 W, so guessing these are on the budget end of the spectrum as with the battery and inverter.

Are there any specific installers that people can recommend who are currently offering decent deals, not sure if posting company names is allowed on here so don't worry if not. I will continue to do some digging.

Screwdriva

https://forums.moneysavingexpert.com/discussion/comment/81883712#Comment_81883712

I wouldn't recommend that quote for two reasons:

1) Those panels have now been discontinued.
2) The battery is an in-house brand. If the installer goes belly up, as unlikely as it may be, so does any support/ warranty claim on that battery. They'll likely never be eligible for the IOF Tariff.

NedS

Potentially use immersion heater in summer once battery is full.

Using your immersion to heat hot water is not efficient. Your solar shouldn't be viewed as free - it currently has a cost benefit of 15p per kWh on SEG tariffs if you export it (assuming you cannot otherwise use or store it).

You can heat your hot water with your existing gas (or oil) boiler at around 6p per kWh, so even allowing for the inefficiencies of a conventional boiler, it's going to cost 2 times more expensive to use the immersion heater, even if it is powered by solar.

tunatuna

Just been looking into intelligent octopus flux.

Really like the sound of this.

Looks like the following battery makes are compatible. Any recommendations on what would be the cheapest? And what would be the most cost effective inverter to pair with it?

tunatuna

What about this as a combination.

Screwdriva

I'd avoid Fox entirely and stick with Tesla if a battery is on the table. Nothing on that list comes close.

Like NedS says, Solar hot water heating makes zero fiscal sense unless you're on a FIT tariff.

Heedtheadvice

You are right Screwdriver regarding solar use ( the different cases for FIT and SEG)... but surely financial not fiscal 😉

I know you are keen on Tesla for obvious reasons but do you have any comment on Fogstar? Several have these batteries ( or the very keenly priced kits) or might be considering them. They do seem to have good specs and excellent customer care and made ( well certainly assembled in Britain) ?