Battery & storage
Pick your home type and backup goal. Get a rough battery size in seconds, no detailed appliance list required.
How it works
Step 1
Match your home size and backup ambition to one of three built-in categories, similar to the presets in the critical loads calculator.
Step 2
No load list or duration input needed, this tool uses typical assumptions behind the scenes.
Step 3
The battery storage size calculator gives a precise number once you're ready to enter actual loads.
This estimator skips the detailed load list and duration inputs that other tools on this site use, instead applying typical assumptions behind three common household categories. The tradeoff is speed for precision: a quick estimate takes seconds and gives a reasonable ballpark, while a detailed calculation takes a few minutes longer but produces a number tailored to your actual loads and goals. Both have their place depending on where you are in the planning process, and the hybrid inverter sizing calculator in our Inverters & Equipment category offers a similarly quick early estimate on the hardware side.
Early in the research process, when comparing rough system costs across different scenarios, or when starting a first conversation with an installer, a quick ballpark figure is often exactly what's needed, without the extra step of listing out every appliance, consistent with early-planning guidance from Ready.gov's power outage preparedness resources. The cost per kWh comparison tool pairs well with this quick estimate for an early budget conversation.
The small category assumes a modest critical loads list over a full day, appropriate for a 1 to 2 bedroom home focused on essentials. The medium category assumes a broader partial home list over a shorter duration, fitting a 3 to 4 bedroom home wanting more comfort circuits covered. The large category assumes a heavier whole home load including HVAC over a shorter backup window, reflecting the reality that whole home systems typically target shorter durations given the much higher power draw involved, a pattern consistent with home-size energy use data from ENERGY STAR's product efficiency database.
Once you have a rough figure, the battery storage size calculator or one of the more specific tools like critical loads only sizing or whole home backup sizing will refine it into a precise, defensible number. If cost is the deciding factor at this early stage, the quick financing comparison tool in our Financing category gives a matching fast estimate on the cost side.
Questions
A quick estimate using home type and backup goal gives a reasonable ballpark, typically within one battery unit of a more detailed calculation for similar households. It is useful for early planning and budgeting, but a detailed load list still produces a more precise number.
A quick estimate works well for early research, comparing rough system costs, or getting a starting conversation point with an installer. Once you're ready to actually purchase a system, a detailed load list gives a more accurate and defensible number.
This tool uses small (critical loads for a 1 to 2 bedroom home), medium (partial home backup for a 3 to 4 bedroom home), and large (whole home backup including HVAC) as three common starting points, each with a typical load and duration assumption built in.
Use this quick estimator for a fast first look, then move to the full battery storage size calculator once you're ready to enter your actual loads and backup hours for a more precise number.