You do not need to climb up on your roof to measure your roof area available for solar. With a digital camera and some high school trigonometry, you can do it from the ground – accurately and safely – here’s how.

Method 1: Counting asphalt shingles to measure your roof area from the ground.

Most asphalt shingles are three feet wide with three tabs. Each tab is got 5 inches of reveal. So by counting these in digital photos you can come up with pretty reliable dimensions. If there is any doubt on the shingle dimensions, you can calibrate the method by measuring a typical shingle in a lower, accessible location.

Method 2. Pythagorean Theorem.

Measure the horizontal run of the roof surface from the ground (‘a’ in the third figure below). Then count the number of shingles to the peak of the roof. Multiple the number of shingles times the width of each shingle (which you can measure at ground level) to get ‘b’ in the figure below. Then calculate the line length of the roof (‘c’ in the figure) using the Pythagorean Theorem; c = square root (a squared + b squared). It is also easy to calculate the roof angle by taking the inverse tangent of b divided by a.

With these simple tricks you can measure your roof area from the ground.  Once you know this, you can figure out how many solar panels will fit, even if you have a complicated roof with many vents.  Here is a post on laying out the solar panels (here). Please let us know how it goes or  if anyone has other methods they would like to share.

Counting Shingles method for how to measure your roof area from the ground

Counting Shingles method for how to measure your roof area from the ground

Counting Shingles TABS method for how to measure your roof area from the ground - length

Counting Shingles TABS method for how to measure your roof area from the ground – length

 

 

 

Pythagorean Theorem to measure your roof

Pythagorean Theorem to measure your roof