The best time to incorporate solar power into the design of a home or building is in the initial construction. Windows are best facing south to let maximum sunlight (hence greenhouse heat) in during the winter. Likewise, avoid windows facing directly into the summertime sun to keep things cooler, so less power is needed for fans or air conditioning. The maximum roof space, however, should always get sunlight exposure.
Keep shade issues in mind when installing solar panels. A panel that loses a quarter of its light can lose half its power production. The main thing to keep in mind is tree foliage. Are any trees going to grow in between the panels and sunlight? Consider trimming them back a little.
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