For one homeowner planning a large rooftop solar installation, the panels were the easy part. Multiple installers agreed on a 37-panel setup for an all-electric home with a heat pump and an EV, but battery recommendations varied sharply.
In a discussion on r/SolarUK, the poster said the property uses about 11,000 kilowatt-hours a year and had received proposals ranging from two or three Sigenergy batteries to a larger Hinen system, raising a common pre-purchase question: How much is enough?
Here's what to know
The homeowner said several companies "all have agreed on 37 panels being the optimal amount for the space available and the sun path," but battery advice varied widely.
Battery sizing can greatly affect both upfront costs and day-to-day savings.
Commenters quickly pointed out that annual electricity use alone does not tell the whole story.
One Redditor advised, "If you're on an EV tariff and only charge during the 'off peak' hours deduct that from your annual usage — this gives you the annual consumption for your house only. Then divide the annual house total by 365 which gives you your average daily consumption."
Batteries often serve two purposes at once: storing solar power generated during the day and shifting cheaper overnight electricity into more expensive daytime hours.
For homes with heat pumps, EVs, or both, a battery that is too small may run out during colder days, while an oversized system could sit underused for long stretches.
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More background
While panel count may be limited by roof shape and sun exposure, storage needs can depend on lifestyle, utility tariff structure, winter heating demand, export rules, and whether you charge an EV at home.
Several commenters said winter performance was the real test.
Another Redditor wrote, "Assuming you charge your EV during off-peak hours, it all comes down to how much does your heat pump consume on an average winter day."
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Battery storage can also make everyday life easier by helping households ride through outages, reduce purchases during peak-rate hours, and keep essential appliances running during severe weather. It can also give homeowners more flexibility to store extra solar energy instead of selling it back when export payments are low.
What can be done?
Several commenters suggested modeling actual household demand in winter rather than relying only on annual totals.
Expandable systems let homeowners start smaller and add capacity later if real-world energy use ends up higher than expected.
Adding battery storage to a solar setup is one of the best ways to protect your home during outages, save money on energy, and go off-grid. It also gives families more control over when they use their power, which can be especially valuable for homes with electric heating and vehicle charging. You can explore EnergySage for information about home battery storage options, including competitive installation estimates.
EnergySage also offers free tools that can help buyers avoid overpaying. For readers in the U.S., EnergySage's solar map shows the average cost of a home solar panel system by state, along with details on solar panel incentives for each state. Together, those resources can help readers get the best price for rooftop solar panels and access available incentives. With EnergySage's help, the average person can save up to $10,000 on solar purchases and installations, making its free comparison services especially useful toward the end of the shopping process.
Where can I learn more?
Sizing is only part of the decision, especially for households also thinking about backup power, financing, and brand reliability. Battery options are widening, from no-money-down home systems to community and utility-scale plans in the U.K. and U.S.
• Homeowners using SunPower and Palmetto can add home backup batteries without upfront costs.
• Jackery has introduced a home battery system with automatic fire suppression and 100 safety safeguards.
• In England, residents raised £440,000 for the UK's first community-owned battery storing surplus solar.
• A new U.K. proposal says neighborhood-scale batteries could cut energy bills by storing cheaper electricity.
Looking at how these projects are paid for and put to use can help homeowners decide whether it makes more sense to start with a smaller system they can expand later or buy more capacity up front.
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