Solar power is becoming a popular alternative for people who want to be energy independent and reduce their environmental impact from energy consumption.
According to the US government’s Environmental Impact Assessment, the average American household uses approximately 877 kWh of electricity per month, which comes out to about 10,600 kWh per year. This figure is an average and can vary depending on the size of the home and individual energy consumption.
So those interested in switching to solar power might be wondering, how many solar panels does it take to power a house?
Average Number of Solar Panels to Power a House
The average solar-powered house needs anywhere between 28-34 solar panels to cover 100% of its energy costs. This number can vary based on the home's size, placement of the panels, geographic locations, and panel efficiency.
What Determines How Many Solar Panels I Will Need?
Several factors determine the number of panels required for a 100% solar-powered home, including but not limited to.
- Total energy usage
- The direction of your roof
- The average amount of sunlight in your location
- Total wattage that your solar panels can produce
To determine your overall energy needs, you can look at your energy bills and make a note of how many kWh you use each month. With respect to the roof, southern-facing roofs tend to get the most sunlight, and the Southwest receives more sunlight than other areas of the country, such as the Northeast.
You can work with a solar professional to determine how many watts you need each panel to produce, and they can help you find options.
How Much Power Can a Solar Panel Produce?
Solar panel technology has made rapid advancements in recent years, resulting in several consumer-grade panels that are highly efficient.
The exact amount of power that your solar panels can produce depends on the amount of sunlight that they receive, which itself depends on the panel’s orientation and your location.
A standard solar panel can produce approximately 250 watts per hour of sunlight. Assuming that your panels get at least 6 hours of sunlight a day, that comes out to about 250 watts x 6 hours of sunlight = 1.5kWh of power per day, approximately 45 kWh per month, and 540 kWh per year. Again, these figures will depend on the amount of sunlight your panel receives and your location.
Assuming that a single panel generates 45 kWh per month and the average American home uses about 900 kWh per month, you would need approximately a minimum of 20 solar panels to cover all your electricity needs.
In reality, you will most likely need more panels than 20 because it is unlikely that they will receive a consistent 6 hours of sunlight every day.
Here are a couple of figures on the average number of solar panels needed to power a 1,000 sq. ft., 1,500 sq. ft, 2,000 sq. ft, and 2,500 sq. ft. home.
- 1,000 sq. feet - 10 panels
- 1,500 sq. feet - 15-16 panels
- 2,000 sq. feet - 22-24 panels
- 2,500 sq. feet - 26-30 panels
How Large Does My Solar Array Need to Be?
All other things being equal, homes in sunnier areas require a smaller array than homes in areas that do not receive as much sunlight. For example, the average size of a solar array in California is smaller than one in Massachusetts because California gets more sun than the Northeast.
A typical solar panel for residential use takes up about 15 sq. feet. For a standard 5 kWh system (~20 panels), you would need about 300 square feet of space. For a 10 kWh system, you would need about 600 sq. feet, and for a 15 kWh system, you would need around 900 sq. feet.
These calculations were made assuming your panels have a 16% energy efficiency. Most residential panels hover between 16%-20% efficiency. If you have more efficient panels, then you would need less space.
(Fun fact: the theoretical maximum efficiency for a single panel solar cell using today’s technology is 33.7%. This figure is called the Shockley-Queisser limit).
How to Calculate How Many Solar Panels You Need to Power Your Home
Ultimately, your best option is to hire a professional and get a quote. But you can estimate the number of panels you will need for your house with some basic math.
- Determine average monthly electricity usage - Refer to your last 12 monthly electricity statements and calculate your monthly energy usage.
- Determine daily kWh usage - Divide your average monthly usage by 30 (ex. 1,000 kWh/30 days = 33.3 kWh per day
- Estimate the amount of sunlight that your panels will receive per day - This can be tricky to determine, but you want a 250 Watt panel to get at least 4-5 hours of direct sunlight per day.
- Determine how much power you want to offset with solar energy - Multiply your daily kWh usage by the percentage of your energy you want to be replaced with solar power, whether it is 100%, 75%, 50%, or 25%.
- Calculate how many panels you will need - Divide the number from step 4 by 250 (1 panel = 250 Watts), and you should have a rough estimate of how many panels you require to cover your energy needs.
Remember that you will likely need more panels than this figure as they most likely will not get sunlight every day of the month.