Not surprisingly, what solar energy companies are looking for are properties that have good exposure to the sun. So, south-facing roofs that aren’t covered by trees are good candidates. But it helps if the roof is in good shape, too.

Because the panels are going to be in place for 20 to 30 years, some homeowners find they need to start with a roofing project before the solar contractors show up. There also may be trees that need to be removed.

Those are expenses above and beyond the price of the solar energy system.

For the Martindales, on Route 149, the ground-mounted solar panels allow Francis Martindale to change the angle of his arrays each month, as the sun rises or sinks in its path across the sky. Most roof-mounted arrays don’t have that option.

Companies like Apex and Monolith, therefore, use electronic, handheld devices that let them project the sun’s location year-round for any particular property. That lets the contractor know if there are shading issues that will impact the solar panels’ efficiency.

The state requires an efficiency threshold — 80 percent of optimal production or better — be met for any project to qualify for full state incentives.