A U.K. homeowner estimated that their 32-kilowatt-hour home battery could power a heat pump for only about 16 hours on the coldest days, underscoring the difference between saving on electricity bills and preparing for extended blackouts.

Here's what to know

The discussion began on Reddit's r/ukheatpumps forum, where a homeowner planning a heat pump installation asked, "Just wondering how you guys spec your battery storage capacity and how many days you could keep the heating on in winter [in] the event of a prolonged power outage." They added that they had 16 kW of solar, 27 kWh of batteries, and a backup gateway.

"We also have the option of upgrading this to 54kWh should needs be," they shared. 

Commenters agreed that cold weather could definitely change the math, including the person with a 32-kWh system. "32kWh of batteries will only just cover our peak consumption," they said. Still, they urged OP to weigh whether such a massive battery upgrade would be worth it. 

"Think you are worrying about this too much - unless your property / area has an actual history of suffering multi-day power outages," they said. 

Energy-efficient upgrades can also alter the equation.

Upgrading heating and cooling is one of the best ways to save on utility bills and protect against rising energy prices, but there isn't just one right system for every home. 

Palmetto helps homeowners understand HVAC options and reduce bills with newer, more efficient HVACs and heat pumps. Its Comfort Plan network can connect you with vetted installers in your area and help you find an efficient system for your home.

More background

For the person with 32 kWh of storage, electricity prices were behind their decision. As they explained, the system's main purpose was to reduce purchases during expensive peak-rate hours, rather than provide several days of grid-free operation.

To estimate their winter demand, they removed the 10 days with the highest consumption from December and January and then averaged the next-highest days. 

As it stands, they expect to have enough stored energy to cover peak-hour consumption on at least 95% of heating days, but they will need to test the system over multiple winters to know for sure. Ultimately, they preferred to save the £4,000 it would've taken to increase battery capacity.

"For capacity which will be lying unused for 99% of the time, it just isn't worth it to us," they shared.

What can be done?

For households considering backup power, reviewing actual winter electricity use can help clarify how much storage they might need. An efficient HVAC can also complement battery storage by reducing the energy needed to keep your home comfortable. 

If you're not ready to spend up front, Palmetto's Comfort Plan includes $0-down options that can lower heating and cooling costs by up to 50%. Palmetto Comfort Plans also include 12 years of free maintenance. 

Homeowners can pair solar panels with electric appliances, including efficient HVACs, to drive utility costs even lower. EasyHome makes it easy to compare solar options and find the best solar system and installer for your home and budget and save up to $10,000 on installations.

Where can I learn more?

Other U.K. homeowners have found that batteries can cut bills even when they struggle to last through a winter night. 

• A homeowner facing £375 winter bills learned batteries could pay off without solar in four to five years.

• In Britain, solar, a battery, and a heat pump kept a 1980s home bill-free for five years.

• A homeowner weighed DIY solar and batteries alongside a heat pump before replacing their boiler.

• A homeowner's outdoor battery lasted until morning before cold nights emptied it by 4 a.m.

• Owners with 5-kilowatt-hour batteries said winter meant topping up from the grid most nights.

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