Evaluating Your Site for Solar Power

When considering solar power in Maryland, DC or Virginia, it’s important to know that only approximately 20% of the homes and businesses in this area will be able to generate energy from solar power. When evaluating your home or business for solar power, Switch to Solar factors in elements that can affect how much solar energy you can produce, such as shading, orientation, and tilt of your roof.


In many residential settings, shading is inevitable. Trees, power lines, buildings and other obstructions all create shade.

When considering where to install your solar panels, we’ll ideally select a location free from shading, or at least one where there is no shading between 9 a.m. and 3 p.m. every day of the year.

Keep in mind that the sun’s path will be lower during the winter months, making shade more likely. If there are any objects such as chimneys or satellite dishes which might cast a shadow on all or part of the proposed space where we’d install your solar panels, we may have to choose a different location.

Evaluating shading patterns can be tricky. The presence of some shading does not rule out solar energy for your home or business. Before you decide that you have too much shade, contact Switch to Solar so that our solar installers can take precise shading measurements.

Orientation and Tilt

The amount of solar energy your solar electric system can produce and the time of year it will produce the most are affected by two factors:

  • The direction it faces (azimuth)
  • The angle at which your solar panels are installed

For homes and businesses in Maryland, DC and Virginia, solar panels facing due south with a 39 degree incline will provide the maximum annual solar energy production. To maximize solar energy production in the summer, your solar panels should face due south with an 18 degree incline.

Solar panel tilt angles should be no more than 15 degrees higher or lower than the latitude of your home or business. When your solar array is tilted at an angle lower than your location’s latitude, your solar energy production will peak during the summer when the solar insolation is greater on horizontal surfaces, but it will be significantly lower in the winter months. The opposite is true if the array is tilted at angles higher than your location’s latitude.

Suggested azimuth limits vary from southwest to southeast at up to 45 degrees east or west of due south. The closer your solar panels are tilted toward horizontal, the smaller the reduction in your solar energy production will be. If your solar array is tilted at latitude and oriented at 45 degrees east or west of due south, it will produce up to 25% less energy from solar power per day, depending on time of year, location, and local weather.

If you’re unsure of your location’s orientation or lattitude, you can use Google Earth to get an overhead view of your property.

You can also use this tool at Solmetric to determine the azimuth of your proposed location.

Available Space for Solar Panels

Consider how much space you have to dedicate to solar panels. A rated capacity of one kilowatt requires approximately 67 square feet.

Because rated capacity for solar panels is not the same as actual electricity generated, Switch to Solar calculates how much electricity your solar panels will actually generate during the year at your site at the proposed tilt and azimuth.

To do so, we use the PVWatts Calculator from the National Renewable Energy Laboratories. If you’d like to try this tool yourself, enter your zip code along with the proposed tilt, azimuth and size of your solar energy system. You can divide the amount of available space by 67 to estimate your solar energy system’s size.

PVWatts uses a default derate factor, which is a calculation that factors in things like transmission loss, of 0.82. You can adjust this number if you like. Also, if you know your per kWh cost of electricity you can enter that as well.

Once you submit these parameters, PVWatts will calculate the average insolation and projected output for your solar energy system, as well as your cost savings.

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