Battery Backup Coverage Calculator

Pick what matters. We'll show you exactly how long the battery runs it.

Most installers will tell you they offer "whole-home backup" without explaining what that means in your house. Pick a battery, pick the loads you actually want kept on, and see real runtime — not a sales pitch.

No email required · No countdown timer · Just the math

1How big is your battery?

Pick a common system, or set a custom size.

13.5 kWh

2How should we estimate your usage?

Quickest answer: plug in your average bill. Want more control: pick what you'd back up, item by item.

That bill works out to — kWh/month, or — kWh/day for your home.
Rates are 2026 regional averages. If you know your actual rate, switch to "By specific loads" for a more precise picture — or send your bill to your remote-consult advisor and we'll plug in your real numbers.

Toggle items on/off. Daily kWh shown is a typical New England household estimate.

Your Backup Result

Pick a battery and a few loads to see your coverage.

—
of backup runtime
0% — 100% of avg home
—
kWh / day selected
—
usable kWh in battery
Real talk: If your panels are producing during the outage, your battery refills as it drains — these numbers assume the worst case (overcast or nighttime).
Book a Remote Consultation No sales pitch. Just real numbers.

What this calculator doesn't tell you

Cold weatherLithium batteries lose 10–25% usable capacity below freezing. If your battery sits in an unheated garage, real runtime will be lower than what's shown here.
Surge loadsThings like well pumps and AC compressors draw 3–5× their running wattage for a split second when starting. A small battery can run them at full load — but not many at once.
Solar chargingIf you have solar and the sun's out, your battery can refill mid-outage. We can model your real PV production in a remote consult — that's a much better number than this calculator gives.