Off-grid living · US
Off-grid power
Size solar and batteries for your worst month, add wind or hydro for the gaps, and heat with a clean-burning stove.
Before
During
- Battery bank = daily energy × days of backup ÷ (usable depth × efficiency). 2
- Add wind or micro-hydro to cover cloudy weeks. A wind, solar and battery hybrid can give reliable round-the-clock off-grid power. 5 6
- Heat with an EPA-certified wood stove. Stoves sold since May 15, 2020 must meet 2.0 grams of smoke per hour, versus 15 to 30 for old uncertified stoves. 7
After
- Put a battery-powered carbon monoxide alarm near sleeping areas whenever you burn fuel indoors or run a generator. 8
Start with what you use
Every power system starts with a load list. For each device, multiply watts by hours used a day, then divide by 1,000 for kWh. 1 The label shows the maximum, so a plug-in meter gives a truer number. Cutting use is the cheapest power you’ll ever buy: every kWh you don’t need is panels and batteries you don’t have to pay for.
Our energy and solar calculator does this math for you.
Solar
Stand-alone solar is sized in two parts: 2
- Array: enough panels to refill the batteries in your worst month. Use NREL’s PVWatts to find peak sun hours for your address. 3
- Batteries: enough storage to carry you through days without sun. Penn State’s example uses about 3 days for 95% availability and about 10 days for critical loads. 2
Usable battery depth depends on chemistry, typically 20 to 80%. 2 Check your battery’s spec sheet.
Grid-tied solar is not backup power
Most home solar is grid-tied, and it switches off when grid power cuts out, for the safety of line workers. Pairing solar with storage is what keeps it running in an outage. 4 If you’re on the grid now and want resilience, ask an installer specifically for a system that can island with batteries.
Wind and hydro fill the gaps
Solar is weakest in winter and on cloudy weeks. DOE notes that a hybrid system combining wind, solar, batteries and/or a generator can provide reliable off-grid power around the clock. 5 Wind needs enough wind where you live, and turbines work best away from buildings and trees that cause turbulence. 5
If you have a stream with a usable drop, micro-hydro runs day and night. DOE’s quick estimate is net head in feet × flow in gallons per minute ÷ 10 = watts. 6 See Living by a stream.
Heat
If you heat with wood, the stove matters:
- Old uncertified stoves emit 15 to 30 grams of smoke an hour. 7
- EPA’s current standard, in effect since May 15, 2020, is 2.0 grams an hour. 7
Cleaner burning means less creosote, less wood and less smoke in your lungs.
Any fuel-burning heater or generator can make carbon monoxide, which you can’t see or smell. Install battery-operated or battery-backup CO alarms near every sleeping area. Never run a generator inside your home or garage, and keep it more than 20 feet from windows, doors and vents. 8
Battery banks and solar arrays store dangerous amounts of energy. Have a qualified installer design the final system and follow your local electrical code.
Sources
- U.S. Department of Energy, Watt Does It Cost to Use It?
- Penn State AE 868, Stand-alone PV system sizing
- NREL, PVWatts Calculator
- U.S. DOE, Solar and Resilience Basics
- U.S. DOE WINDExchange, Small Wind Guidebook
- U.S. DOE Energy Saver, Planning a Microhydropower System
- U.S. EPA Burn Wise, Choosing the Right Wood Stove
- CDC, Carbon Monoxide Poisoning: Basics