Homes · Site note
When to walk away from a flat project
Updated
Walk away if the only location is a common hall, the freeholder will not answer, the supply is shared and undocumented, or the quote assumes 0% VAT and a balcony cabinet with no drawings. A house move can be cheaper than forcing a bad location.
On the actual building
The opening is the claim. What follows is how I would test it against a bill, a cupboard and a connection form. The cupboard, the supply and the tariff decide it. A national package price skips all three.
In Manchester, on Electricity North West, 5 kW sits above the 3.68 kW G98 line, so this wants a G99 application before anyone energises it. Export can still be capped. Agree that before the inverter is ordered. The figure uses 8 kWh and 2.5 kWp, which is enough to tell two quotes apart if they assumed something else.
If the house is in Manchester
Manchester is only an example for "When to walk away from a flat project", not the only place the point applies. Electricity North West would be the network if the survey were there, and the cupboard rules would still win.
The money
Take an 8 kWh pack, cycled about 280 times, at 90% round trip. Charge at 9.0p, and value what comes back at 27.2p. Export given up is priced at 6.0p. About 800 kWh a year of the charge is treated as spare solar from 2.5 kWp that might otherwise have been exported. Delivered energy is about 2016 kWh. After charging cost and lost export, the figure saves about £380 a year. Set that against £5,855 fitted, which is a September 2026 illustration at the temporary 0% residential rate, not a quote. That is a simple payback of about 15.4 years on these assumptions. Nudge the night rate up by 4p and see if you still like it.
Where the job is a qualifying install in a home, the 0% rate runs to 31 March 2027 and is due to become 5% after that. This figure prices the work at £5,855 on that basis. It does not apply to a shop, and it does not apply to a battery you buy and fit yourself.
When to stop
I would not pay the bulk of £5,855 before the DNO route for a 5 kW inverter is known.
If the only place for a 8 kWh cabinet is an escape route, a hot boiler cupboard or an unapproved balcony, stopping is a successful survey.
Before a deposit, I would want usable capacity, the warranty counterparty and a G99 note for this 5 kW inverter. The cupboard has to be a place you can stand in, at a temperature the datasheet allows. A five-minute video is not that.
Common questions
Is the price on this page a quote?
No. £5,855 is a September 2026 illustration for a 8 kWh example at the temporary 0% residential rate. Your survey replaces it.
Will it stay on in a power cut?
Only if a gateway or essential-load board was designed and paid for. A standard grid-tied battery turns off with the grid. On this 8 kWh example the inverter is 5 kW, and backup is still a separate line.
What paperwork should I keep?
Keep the MCS certificate where the job is certified, the electrical certificate, the DNO record, the schematic, the warranty registration and a photo of the schedule. For an illustrated £5,855 job, that folder is part of what you bought.
What if the cheap rate is not 7p?
Then the figure changes. This page used 9.0p as a charge rate and 27.2p as the rate avoided. A smaller gap means a worse payback. Read the live tariff.
Sources
Want a price for your house?
The figures above are a rough guide. An installer still needs to see your fuse board, where the battery will go, and whether you want power during a blackout.