backuppowercalc
Load-accurate sizing

Most generators are sized for the wrong number. The surge.

When a well pump or AC compressor starts, it pulls two to three times its running watts for a split second. Size for the steady load alone and your generator stalls at the worst moment.

Live surge demo tap to add loads
Running0W
Peak surge0W
Add a motor and watch the peak jump past the steady draw.
2–3×
Surge multiplier on motor startup — the number most calculators ignore
1 load
Only the largest motor surges at peak — not all of them at once
20%
Safety margin applied before we recommend a wattage class
How it works

From your actual appliances to the right unit

No square-footage guesswork. You tell us what you need to keep running; we calculate the true simultaneous peak — including the one surge that matters — and recommend what to buy.

STEP 01

List your loads

Choose the appliances you need during an outage. Each carries real running and starting watts from a sourced dataset.

STEP 02

We find the true peak

We add your running load to the single largest startup surge — the correct method — and flag the dominant load.

STEP 03

Get matched to a unit

A recommended wattage class, three real options from budget to premium, and a fuel-type call.

Calculators

Pick the tool for your situation

Whole-home load sizer

Size a generator or battery from your exact appliance list, surge included.

Starting-watt calculator

Find the true startup surge for motors, compressors, and pumps.

Fuel-type comparison

Gas, propane, dual-fuel, inverter, or battery — side by side.

Generator vs. battery

Which fits your outage frequency, budget, and loads.

Runtime calculator

How many hours a tank or battery lasts under your load.

Transfer switch & wire sizing

NEC-based switch amperage and wire gauge for your generator.

NEC dwelling load calculator

NEC service-load calc — optional (220.82) and standard methods, surge-accurate.

Altitude & temperature derating

How much real output your generator loses to elevation and heat.

EV charging on backup power

Charge a Tesla or F-150 Lightning alongside your home — with the battery reality.

What can my generator run?

Flip appliances on a live breaker-box gauge and watch for the overload.

Size from your smart energy monitor

Upload an Emporia Vue or Sense CSV and size from your home's real measured demand.

Blackout runway: how long will it last?

Live countdown of your backup hours as you toggle appliances and fuel.

Extension cord size & safety

The safe cord gauge to run an appliance a given distance — and the max length for a cord you own.

Generator plug & inlet guide

The exact NEMA plug, inlet, and safe connection path — never a DIY suicide cord.

Generator cost of ownership

What a gas generator really costs over 5 years — purchase, fuel, and upkeep.

Standby install quote

Get matched with local installers for a whole-home system.