How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Phil Your Own Question
Phil, Mechanical Engineer
Category: Electrical
Satisfied Customers: 8768
Experience:  Retired electrical contractor, 51 years experience.
Type Your Electrical Question Here...
Phil is online now
A new question is answered every 9 seconds

What is the best angle from the horizontal for solar panels

This answer was rated:

What is the best angle from the horizontal for solar panels in the D.C.?
Welcome to Just Answer!

The correct angle depends on which compas direction the panels are facing... if you can give me that direction precisely, such as 'due south' or 'south west, 20 degrees from west' and any local shading conditions that block the sun during part of the day I can give you an optimum angle.

Customer: replied 4 years ago.

There is no shading and the panels can be north, east, south or west.


Let's make it facing West.




South facing is by far the most optimal... west facing will give you about 30% less efficiency due to lack of a good angle before noon on a pitched roof application.



The latitude for Washington DC is 39 degrees, to get the best sun angle for winter operation multiply 39 by 0.9 then add 30 degrees... thats 35 + 30 or 65 degrees from horizontal.


If you want to optimize for year round use, adjustable pitch mounting frames are better. CLICK HERE FOR AN ARTICLE ON THAT.

We can go from there until your question is fully answered as long as you rate my answer so far *positively... I will hold your question open.


Phil and 2 other Electrical Specialists are ready to help you
Customer: replied 4 years ago.
The panels would be on a flat roof that has an East West longitudinal direction and if it were to be pitched the pitch would be facing West .
You will get the most out of the panels if you face them south on adjustable frames so they can be at 65 degrees from horizontal in the winter. and at progressively less of an angle towards summer.... the ideal angle is at 90 degrees to the sun at mid day.

Tell me please what size the panels are, and how many of them you are using.

We can go from there as long as you rate my answers *positively, there is no time limit in that case.