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Find out how much battery storage your solar system needs. Enter your daily energy use and backup requirements — get instant results in kWh and Ah. All calculations run in your browser; no data is uploaded or stored, no signup required.
How solar battery sizing works
Sizing a solar battery bank comes down to three steps. First, multiply your daily energy consumption by the number of days of autonomy — how long the battery must carry your loads with no solar input. That gives the usable energy you need.
Second, divide by depth of discharge (DoD) and inverter efficiency to get the nominal battery energy. A LiFePO4 battery at 90% DoD with a 92% efficient inverter needs about 1.2× the usable energy in nameplate capacity.
Third, convert to amp-hours at your system voltage (Ah = Wh ÷ V) and round up to whole battery units. For home solar, 48V (51.2V nominal) systems are the standard choice — lower current, thinner cables, easier expansion.
Frequently asked questions
How do I size a battery for my solar system?
Multiply daily kWh consumption by days of autonomy, then divide by (DoD × inverter efficiency). The calculator above does this automatically and converts the result to Ah at your system voltage.
How many days of autonomy do I need?
Two days is the common default for grid-tied homes with solar; off-grid cabins in cloudy regions often use 3–5 days. More autonomy means a larger, more expensive battery bank.
What depth of discharge should I use for LiFePO4?
LiFePO4 batteries safely support 80–100% DoD, far deeper than lead-acid (50%). Using 90% is a balanced default that preserves long cycle life.
Does inverter efficiency really matter for sizing?
Yes. A 92% efficient inverter wastes 8% of battery energy as heat. Ignoring it undersizes your bank by roughly that percentage — enough to matter on cloudy stretches.
Can I expand the battery bank later?
With modular 51.2V 100Ah wall-mounted units, yes — you can parallel additional units as your needs grow. Size for today, expand tomorrow.
Power your solar system with LiFePO4 storage
Modular 51.2V 100Ah wall-mounted batteries — size for today, expand tomorrow. OEM/ODM and bulk orders welcome.
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