About OutageWatt & how the math works

OutageWatt is an independent website of free tools for one question: when the grid goes down, what keeps your house running, and for how long? It compares the three realistic answers side by side, a portable power station, a home battery and the EV in your driveway, against the appliances you actually can't lose. It is published by Pearl Digital LLC, a Wyoming limited liability company (filing No. 2026-002043540).

The method, in full

1. What you need to run

Every appliance has three numbers: its running watts, its starting (surge) watts and its duty cycle, the share of time it actually draws power while it is switched on. A refrigerator's compressor runs roughly a third of the time; a TV runs the whole time it is on. Daily energy is running watts × duty cycle × hours of use. Each value is cited on the planner next to the appliance.

2. Output and starting power

The continuous output you need is the sum of the running watts of everything you selected, because during an outage it can all be on at once. The starting power adds the largest single motor surge on top, since two compressors rarely kick in during the same second. A unit that can't cover that peak trips or refuses to start the motor, even when it has plenty of stored energy.

3. How long it lasts

Runtime comes from a quarter-hour simulation: the battery drains at your average draw divided by inverter efficiency (88% for portable stations, 90% for home batteries), and refills with solar during the day. Solar follows a sine curve from 6 a.m. to 6 p.m. at 75% of panel rating, which works out to about 4.3 peak-sun hours on a clear day. Cloudy storm days produce less, and we say so wherever solar appears.

4. Product specs and prices

Capacities, outputs, surge ratings, solar inputs and prices come from each maker's official US product page or spec sheet, with the check date shown next to them. Home battery installed prices are ranges reported by public marketplaces, never quotes. When a figure only exists from third parties, we label it.

What we don't do

• We don't sell or install anything, and we are not an installer lead network.
• We don't invent reviews, ratings, test results or “hands-on” claims. Estimates are labeled as estimates, with the assumptions shown.
• We don't let affiliate relationships change a calculation or a ranking. See our affiliate disclosure.
• We don't give electrical, medical or tax advice. Connecting anything to a home panel needs a licensed electrician and a transfer switch or interlock.

Corrections

Spotted an outdated price or a wrong spec? Write to hello@outagewatt.com with a link to your source. We check every report and update the data file and its date.

OutageWatt is independent and not affiliated with, endorsed by or sponsored by Tesla, Enphase, FranklinWH, Ford, GM or any power station brand. Product names and product photos belong to their owners and are used only to identify the products.