Tools / Sizing calculator
Free tool · 2-minute setup

Size your power system the right way.

Tell us what you want to run and for how long. We estimate the battery, surge wattage, and matching kit from inventory — with optional solar and wind input. Built on the manufacturer's stated specs.

Pick a scenario ↓ Build custom
15+ appliance presets 0 products matched live Estimator only · Confirm specs with the manufacturer
Quick start

Pick a scenario

Most outages fall into one of these four use cases. Click one to pre-fill the calculator below — then fine-tune in custom mode.

Custom build

Or build your own

Pick exactly what you need to run, for how long. Each appliance has typical wattage built in.

Appliances

Tap to select. Slide to adjust hours per day.

Add solar + wind generation

Pair the battery with solar panels and a wind turbine to recharge during the outage. Reduces battery capacity needed for longer runtimes.

Pacific NW (3)US avg (5)Southwest (7)

Show recommendations from

Filter which brands appear in the recommendation. All checked by default.

Your match

Updates as you adjust inputs
Energy needed
0kWh
Peak surge
0W
Continuous load
0
Runtime estimate
0
No appliances selected Pick a scenario above or check appliances
to see your recommended kit.
How matching works

Buy the right size. Not the biggest box.

The calculator is conservative — it sizes for full sustained load. In real outages, fridges cycle ~30% of the time and ACs cycle ~60%, so the actual battery you need is often smaller than this tool suggests. For medical, whole-home, or business-critical use, confirm fit with the manufacturer's technical support before ordering.

Email a question Adjust my inputs
01

Battery capacity

We pick the cheapest battery whose usable capacity (after DoD + inverter loss) covers your total load × duration, minus solar and wind contribution.

02

Surge wattage

Refrigerators, well pumps, and ACs spike up to 4× their running watts when starting. The recommended kit must handle that surge.

03

Solar + wind contribution

Adjustable sun hours (3–7/day) and wind capacity factor. Adds back into your runtime so the battery can be smaller.

04

Confidence margin

If your peak surge exceeds the smallest fitting battery, we automatically bump up — surge mismatch is the #1 cause of backup failure.