A U.K. homeowner with a small, four-panel solar setup found out that a 10-kilowatt-hour battery paired with a cheap overnight electricity rate might extend the estimated payback period by over a year.
The quote was £4,680 ($6,251) for a 3.7-kilowatt AC-coupled inverter and the battery.
Here's what to know
In a Reddit thread, the setup in question was for a detached home with a modest 1.6-kilowatt solar array. The poster said the household used 3,000 to 3,500 kWh a year before adding overnight charging for an Audi e-tron. Their EDF Energy tariff charged 32.703 pence during the day and 6.660p at night.
The difference made battery arbitrage seem compelling.
"I'm finding it hard getting exact pricing online without having to sign myself up for spam calls," the homeowner wrote. "Is a 3-4 year payback even remotely possible on the above figures?"
For homeowners in that position, EnergySage can be a useful place to explore home battery storage options and competitive installation estimates. EnergySage has teamed up with electrification brand Qmerit to help homeowners get the best price on home battery storage solutions.
A local electrician supplied the quote and warned that the array "may not fill the batteries during the day and may need an off-peak top up."
"Based on your figures, no," one commenter wrote. "It's going to be more like 5-6 years — maybe longer if the overnight rates increase and day rates drop."
Crushed by your bills? See instant solar savings from vetted installers in just a few clicks With energy prices through the roof, there's never been a better time to go solar — and EasyHome can help you find the best prices from the best installers in your area. EasyHome takes the guesswork and headaches out of energy upgrades by showing you estimated savings from a network of vetted local partners. To get started, just enter your ZIP and share a few details about your home — seeing your estimate is really that easy. |
More background
Using the quote as a starting point, one user said the return would take 4.9 years. The estimate assumed the house used 10 kWh a day and cycled the full battery daily, with each shifted unit avoiding about 26p of daytime electricity — £2.60 in daily savings, or £949 a year.
The commenter called a 10-kWh battery "the right size." However, with only a 1.6-kilowatt solar system, keeping it full may rely more on overnight charging than on daytime solar generation.
"Battery installation should be VAT-free if MCS certified," one commenter wrote, while another clarified, "The rate of VAT is zero, but it should still be billed at zero — and appear on the invoice as such."
Someone else said £4,680 was expensive, pointing to a cheaper example in a linked r/PlugInSolarUK comment. Another person linked to an eBay listing for £3,900, while another commenter noted that local install costs and battery and inverter brands can shift the total.
What can be done?
Battery storage can keep key household loads running when the grid goes down, so many buyers look beyond a years-to-payoff calculation.
The thread pointed to next steps, including asking the installer about MCS certification and VAT treatment, getting competing quotes, and verifying whether the battery and inverter brands justified the price difference.
Since the house had only four panels, another question was how much of the battery's charging would realistically come from solar?
For households that want backup power without going to a large system, Pila offers plug-and-play batteries at a fraction of what whole-home backup systems cost.
In the thread, the original poster sounded unconvinced by the three-to-four-year estimate, replying to the first commenter: "Yeah, the maths doesn't work as I'd like. However, I guess the better question would be is the installation estimate a realistic figure?"
Get TCD's free newsletters for easy tips, smart advice, and a chance to earn $5,000 toward home upgrades. To see more stories like this one, change your Google preferences here.
