The solar panel system for a typical 2,000-square-foot house is 18 to 25 400-watt panels. That equals roughly 7.2 to 10 kilowatts of solar capacity.
A home close to the 2024 U.S. residential average of 10,380 kilowatt-hours per year would need about 19 panels, or a 7.6 kW system.
| Home electricity use | Approximate 400-watt panels | Approximate system size |
|---|---|---|
| 8,000 kWh per year | 15 panels | 6.0 kW |
| 10,000 kWh per year | 19 panels | 7.6 kW |
| 12,000 kWh per year | 22 panels | 8.8 kW |
| 15,000 kWh per year | 28 panels | 11.2 kW |
| 20,000 kWh per year | 37 panels | 14.8 kW |
These figures use average U.S. solar conditions. Your electricity use and location matter more than the home's square footage.
Why Does a 2,000-Square-Foot House Need 18 to 25 Panels?
A 2,000-square-foot house falls in this range when its electricity use and solar production are close to the U.S. averages.
The U.S. Energy Information Administration reported average residential electricity use of 865 kWh per month in 2024, or about 10,380 kWh per year.
The National Renewable Energy Laboratory estimates an average residential solar capacity factor of 15.7% across the contiguous United States. Location-specific estimates range from about 12.7% to 19.6%.
At the national average:
- One 400-watt panel produces about 550 kWh per year.
- A home using 10,380 kWh annually needs about 19 panels.
- The same home may need about 15 panels in a high-solar location or 24 panels in a lower-solar location, before shade, roof angle and system losses are included.
What Changes the Number of Solar Panels?
Annual Electricity Consumption
Electricity use is the main factor. A 2,000-square-foot home with gas heating and efficient appliances may use much less electricity than an all-electric home of the same size.
Usage may be higher with:
- Electric resistance heating
- A heat pump
- Central air conditioning
- An electric water heater
- A swimming pool or hot tub
- An electric vehicle
- A well pump
- Frequent use of a workshop or outbuildings
Start with the total kWh shown on your last 12 months of electricity bills.
Location and Sunlight
Solar panels produce different amounts of electricity in different locations. An identical rooftop in Arizona will usually produce more energy each year than one in Washington because the Arizona roof receives more usable sunlight.
The U.S. Department of Energy recommends using NREL's PVWatts Calculator for an address-specific estimate. PVWatts accounts for location, system size, roof orientation, tilt and other performance factors.
Roof Direction and Shading
A south-facing roof generally provides strong annual production in the Northern Hemisphere. East- and west-facing roofs can also work well.
Trees, chimneys, nearby buildings and other roof obstructions can reduce production. The Department of Energy lists electricity consumption, system size, roof direction and available sunlight among the main factors affecting solar production and savings.
Panel Wattage
The estimates above use 400-watt panels. The panel count changes when the wattage changes:
- 350-watt panels: More panels are needed.
- 400-watt panels: About 18 to 25 panels for many average-use homes.
- 450-watt panels: Fewer panels may be needed for the same system size.
Panel wattage sets the system's nameplate capacity. It does not determine annual energy production by itself. Sunlight and installation conditions also affect output.
How Do You Calculate the Exact Number?
Divide annual electricity use by the expected production from one kilowatt of solar at your address. Then convert the required system size into the number of panels.
- Find your annual electricity use in kWh.
- Use PVWatts to estimate how many kWh one kilowatt of solar will produce at your address.
- Divide the required system size by the wattage of your chosen panels.
For example:
- Annual electricity use: 10,380 kWh
- Estimated production: 1,375 kWh per installed kW
- Required system size: about 7.5 kW
- Panel size: 400 watts
- Estimated panel count: about 19 panels
Round up to the next whole panel. Leave room for added capacity if you expect to install an electric vehicle, heat pump or another major electrical load.
Do Solar Panels Keep the House Running During a Power Outage?
Usually, no. A standard grid-tied solar system normally shuts down during an outage for electrical safety. Solar panels can reduce or offset grid electricity use, but they do not provide backup power when the grid is unavailable or at night.
A backup-capable system usually needs:
- Solar panels
- A compatible inverter
- Battery storage
- Critical-load or whole-home backup wiring
The Department of Energy explains that batteries store solar electricity for use when the panels are not producing, including at night.
Bottom Line
Square footage provides a rough starting point, but annual electricity use determines the system size. Use your last 12 months of bills and an address-specific PVWatts estimate before choosing the final panel count.