How we calculate

Running and starting watts come from Champion Power Equipment's published wattage chart. Champion gives a range for each appliance. We use the top of the range, so results err on the safe side. You can edit any number in the calculator to match your own appliance's label.

Fridges and freezers cycle on and off, so for battery sizing we use measured daily energy instead of running watts: the median of ENERGY STAR certified models, from ENERGY STAR's open data. A full-size fridge comes to about 1,400 Wh a day and an upright freezer about 1,350 Wh. If you change a fridge's watts or hours, we switch to watts × hours.

Hours of use per day are our defaults, not measurements. Change them in the power station calculator.

running = Σ running watts × quantity

starting = running + the largest single start-up surge

recommended running = running × 1.2, rounded up to the next 100 W

We add only the largest surge because motors rarely start at the same moment. That's Champion's method. We add 20% headroom so a generator doesn't run at its limit. You can change it under Advanced.

Generators make less power on propane. Champion puts the loss at about 10%. When you choose propane, we check each model against its published propane rating and leave out gas-only models.

energy = Σ watts × hours of use × quantity for the length of the outage

capacity = energy ÷ 0.85 × 1.2, rounded up to the next 10 Wh

The 85% is inverter efficiency: the share of stored energy that reaches your appliances as household AC. A power station also needs output at least equal to the running total, and surge at least equal to the running total plus the largest start-up.

For outages under a day, each appliance counts its hours of use up to the length of the outage. A CPAP used 8 hours in a 12-hour outage counts 8 hours. Fridges and freezers count their daily energy pro-rated by the hour.

Some brands publish a "power lifting" rating that only works for heaters and kettles, not motors. We don't count it as surge.

We suggest one type, using these rules in order:

1. Standby generator if you include central air, an electric water heater or an electric dryer, or if you need more than 9,500 W running, the largest portable generator we list. Standby sizes are the next of 10, 14, 18, 22, 26 kW above your running need.
2. Power station if you include a medical device and a model we list can power it.
3. Power station if the battery you need is 2,100 Wh or less and a model we list fits.
4. Portable generator otherwise.

These are starting rules, not laws. The calculator always shows all three options, so you can choose.

Each model's specs come from the manufacturer's own product page. We check them by hand and list the date. A model passes only if it meets every number. We don't rank models by commission, and we don't call anything a top pick.

This is a planning tool, not an electrical design. Hardwired loads such as well pumps and furnaces need a transfer switch fitted by a licensed electrician. A standby generator needs a professional load calculation and install.

Run generators outdoors only, more than 20 feet from windows, doors and vents, and never in a garage (CDC). If you rely on a medical device, ask your provider about a backup plan.