Should the roof of a house or commercial building face a certain way to install a solar PV system? The short answer is “yes”, but we have a lot of flexibility in the design to meet the needs of the customer. First and foremost, Colorado is in the Northern hemisphere and not at the equator, the Sun never tracks from true East straight overhead to set in the true West. The Sun tracks a Southerly arc during every season, more in the Winter than the Summer but still to the South. Therefore we won’t ever install a PV system on the North face of a roof. The direction that is best to face solar panels is always going to be South in Colorado. However that does not mean that East and West are not suitable, quite the contrary. East is the second best orientation as it gets very direct sun light from dawn until early afternoon, and West gets direct sun light from midday till dusk. The reason East is better than West, is that our weather patterns tend to favor afternoon thunderstorms and cloud cover. That partially blocks some of the sun’s rays from reaching the PV panel. A more important question is “do I have enough roof space…to get enough solar PV installed…to produce enough electricity…to meet my goals?”. An example is: if it would take 20 solar panels on a South facing roof to meet your needs, an East or West roof might require 22 or 23 panels to do the same work, the install price difference is typically negligible and if you can fit the 22/23 panels on your roof you really don’t need to be concerned with efficiency issues.