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An off grid solar power system makes your own electricity from the sun, stores it in batteries, and runs your home with no connection to the utility. It’s a great goal, but it’s also widely misunderstood. A whole-home system is a serious installed project, while a portable solar generator is a much smaller backup tool. This guide explains the components, the sizing basics and what you can realistically expect, so you can decide which one you actually need.
Why going off-grid is in the news
On September 30, Defense Secretary Pete Hegseth announced FORTRESS America, an initiative to make major U.S. military bases able to run on their own power instead of the civilian grid. According to Pentagon documents reviewed by Fox News, major bases in the continental U.S. are being asked to plan to sustain essential operations for at least 90 days on their own. The Pentagon hasn’t released the memo publicly, and Snopes rates the reporting “mostly true.”
Your house isn’t a military base, and you don’t need 90 days of independence to benefit. But the same question applies at home: what would you keep running if the grid went down, and for how long?
What is an off grid solar power system?
The South Carolina Energy Office puts it simply: off-grid systems are not tied to any utility power lines, and they’re most common in remote areas where connecting to the grid costs more than buying an off-grid system. In an off-grid home, the solar system is the main source of power. Batteries store unused solar energy for night, and generators, small wind systems or other fuel sources are sometimes used as backup when the batteries run low.
Solar power for remote homes isn’t new. The U.S. Energy Information Administration (EIA) notes that by the late 1970s, solar panels were already providing electricity in remote, off-grid locations without power lines.
The main components
According to the South Carolina Energy Office, an off grid solar power system typically includes:
- Solar panels mounted on the roof or ground. They produce direct current (DC) electricity.
- A charge controller to prevent overcharging the battery.
- A battery bank to store energy for night and cloudy days.
- An inverter to convert DC into the alternating current (AC) your outlets and appliances use. The EIA notes that inverters are what convert the DC output of solar panels into AC.
- Junction boxes and wiring that connect the panels to the home’s breaker panel, plus a connection for a backup generator.
- A meter or monitor showing how much power you use, produce and have stored.
Off-grid vs. grid-tied vs. battery backup
This is where many people get surprised. Before you plan an off grid solar power system, know the three common setups:
- Grid-tied: panels connected to the utility grid. The South Carolina Energy Office notes these include a disconnect switch that, for safety, prevents the system from sending power to the grid during outages (called islanding).
- Grid-tied with battery backup: adds a battery bank, and power stored in the batteries can be used during outages.
- Fully off-grid: no utility connection at all. The batteries, panels and any backup generator must cover everything.
If outage protection is your main goal, the battery is the piece that matters. Rooftop panels without storage are designed to work with the grid, not replace it.
Sizing basics: how big an off grid solar power system do you need?
Sizing comes down to four numbers. Work through them in order.
1. Daily energy use (watt-hours)
List everything you want to run. For each item, multiply its watts by the hours you’ll use it per day. A 100-watt device running for 5 hours uses 500 watt-hours (Wh). Add them up for your daily total. The appliance label or a plug-in watt meter gives you the real numbers.
For perspective, the EIA says the average U.S. residential utility customer bought 10,791 kilowatt-hours (kWh) of electricity in 2022, about 899 kWh per month. That works out to roughly 30 kWh, or 30,000 Wh, per day. Louisiana averaged the most (14,774 kWh a year) and Hawaii the least (6,178 kWh).
2. Battery storage
Multiply your daily use by the number of days you want to ride through without sun. Two cloudy days at 10 kWh a day means about 20 kWh of usable storage.
3. Solar array
Your panels need to refill the batteries on an average day in your worst season. Output depends on your location, the season, weather, shading and panel angle, so a site-specific estimate from an installer is worth getting.
4. Inverter size
The inverter must handle the total wattage of everything running at once, plus the surge when motors in things like pumps start up. Large HVAC systems and full-home panels may also need 240-volt output.
Realistic expectations for a whole-home system
Here’s the honest part. Running an average American home on an off grid solar power system means producing and storing something like 30 kWh a day, every day, including in winter. That calls for a large solar array, a big battery bank, a properly sized inverter, a backup generator for long cloudy stretches, and professional design and installation. The U.S. Department of Energy notes that installation costs include permitting and inspection, and the South Carolina Energy Office suggests consulting your solar installer about battery options.
The single best way to shrink the system is to shrink the load. Efficient appliances, LED lighting and non-electric options for heat and cooking all cut the daily watt-hours your panels and batteries have to cover.
Where a portable solar generator fits
Most families don’t need, or want, to leave the grid. What they want is power for the essentials when the grid fails. That’s where a solar generator makes sense: an all-in-one battery, inverter and charge controller you can recharge with panels.
Small: phones, lights and a CPAP
The Grid Doctor 300 Solar Generator pairs a 320Wh LiFePO4 battery and 300W pure sine wave output with a 100W solar panel, and the generator weighs about 8.6 pounds. My Patriot Supply says it’s built for phones, laptops, lights, routers and medical devices such as CPAP machines, and is not designed for full-size refrigerators, microwaves, sump pumps or space heaters.
Larger: refrigeration and multi-day outages
The Grid Doctor 3300 Solar Generator offers 3,300W continuous output (6,600W surge) and a 2,048Wh LiFePO4 battery that can expand to 16,384Wh with up to seven expansion batteries. It accepts up to 1,000W of solar input, includes a 200W waterproof panel, and has four standard 120V outlets plus a 30A RV outlet. My Patriot Supply positions it for multi-hour to multi-day outages where refrigeration, lights and communications matter. It also includes what the maker calls EMP Intercept Technology, designed to help protect connected electronics from surges and electromagnetic disturbances.
Be clear-eyed about the limits. Even fully expanded, 16,384Wh is a little over half of the average home’s daily use, and the 3300 doesn’t offer 240V output for large HVAC systems or full-home panels. It’s a strong backup for the essentials, not a substitute for a whole-home off grid solar power system. For a deeper comparison, read Grid Doctor 300 vs 3300 and our guide to the best solar generator for home backup. If you need more output, our 5000 watt solar generator buying guide covers the next step up.
A simple plan to get started
- List your must-run devices and add up the watt-hours per day.
- Cut the load where you can: LED lights, efficient appliances, non-electric heat.
- Decide on your goal: essentials during outages, or full independence.
- For essentials, choose a solar generator sized to your daily watt-hours. The Grid Doctor 3300 covers refrigeration-level needs; the 300 covers small electronics.
- For full independence, get quotes from qualified installers for a designed and permitted off grid solar power system.
Power is one part of the picture. Our power outage emergency kit guide covers food, water, heat and light too.
Frequently asked questions
How big of an off grid solar power system do I need?
Start with your daily watt-hours. The average U.S. home bought about 30 kWh of electricity a day in 2022 according to EIA data, but a home that cuts its electric load can need far less. Add up your own devices to find your number.
Does grid-tied solar work during a power outage?
Not on its own. Grid-tied systems include a disconnect that stops them from sending power to the grid during an outage. To use solar power when the grid is down, you need battery storage.
Can a solar generator power a whole house?
Not a typical one. Portable solar generators are best for essentials. Even an expandable unit like the Grid Doctor 3300 stores less than an average home’s daily use and lacks 240V output.
What does an off-grid system need besides panels?
A charge controller, a battery bank, an inverter, wiring and junction boxes, a meter or monitor, and usually a backup generator.
The bottom line
An off grid solar power system is very doable, but a whole-home setup is a big, professionally installed project sized around your real daily energy use. For most families, the smart move is to cut the load, protect the essentials with a solar generator, and grow from there.
Sources: South Carolina Energy Office: Off-Grid, SC Energy Office: Grid-Connected, SC Energy Office: Battery Back-up, EIA: Household Electricity Use, EIA: Photovoltaics and Electricity, U.S. DOE: Homeowner’s Guide to Going Solar, Fox News, Snopes. Product details are from My Patriot Supply product pages as of October 27, 2026.