Off the grid, every light, every pot of coffee and every turn of the well pump is yours to power. There’s real freedom in that, and a little planning goes a long way.
Whether you’re setting up a cabin for weekends or a ranch home far from the nearest power line, our calculator helps you size a generator, a battery bank and a solar array from the appliances you actually plan to run.
Home & Ranch Living · Land & Utilities
The Off-Grid Power Calculator
Check what you’ll run, and we’ll size the generator, batteries and solar. Your answer updates as you go.
What will you run?
Check each appliance and enter the hours a day it actually runs. A refrigerator cycles on and off, so a few hours a day is typical.
Much of the sunny West sees about 5 to 6 peak sun hours a day, with less in winter. More backup days means a bigger battery bank.
Generator to look for
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running watts
Estimates only, for planning. Not an electrical design. Never run a generator indoors, and always use a licensed electrician.
Off-Grid Power Questions, Answered
Where do these numbers come from?
We’re not electricians. Appliance running and starting watts come from Home Depot’s guide to choosing the right size generator, which notes that motors can need about three times their running watts to start. A few items, like LED lights, a laptop and internet, a propane furnace blower and shop tools, are our own estimates. The solar and battery sizing uses common rules of thumb: usable battery capacity of about 80 percent, and about 25 percent lost to wiring, inverters and weather.
What size generator do I need for a cabin?
Add up the running watts of everything you’ll use at the same time, then make sure the generator can handle the extra surge when the biggest motor starts, like a well pump or refrigerator. Many cabins run happily on a quiet inverter generator around 2,200 watts. A well pump or air conditioner usually calls for a larger one.
How big a solar system do I need off the grid?
It depends on how much energy you use each day, not just how many appliances you own. Divide your daily kilowatt-hours by your peak sun hours, then add room for losses. A cabin might need only a small array, while a full-time ranch home can need a large one plus a substantial battery bank.
Solar, batteries or a generator?
Most off-grid places use all three: solar for everyday quiet power, batteries to carry you through the night and cloudy days, and a generator for long stretches of bad weather or big loads like a welder.
Read our guide to off-grid power for a cabin and whole-house generators, then see the raw land setup cost calculator and all of our ranch calculators.