There’s a configuration to installing solar panels. The rules that are all pretty rigidly prescribed. There’s also a direction they face: South. However they might actually be facing the wrong way.

Photograph: Cultura/Rex.

By having them face south — which almost all the rooftop panels in the U.S. do — they’re in peak position to catch a face full of sun at both rise and set, thereby collecting the most total watts per day.

The problem is that, even if those are the peak time to gather solar energy, those are not the peak times to use energy. If we wanted to lower the total stress on the power grid, a better choice might be installing them to face west, which would result in more energy in the afternoon when energy usage is at its height.

At this point in most parts of the US, there is plenty of electricity available from other sources in the morning and midday. Crunch time is late afternoon, when temperatures are higher and air-conditioners are working hard, and inefficient plants running on natural gas or even coal are cranked up to the maximum. At  that point, the declining sun is hitting the solar panels at an oblique angle, reducing power output. “The needs of the grid may mean that they should be pointed west,” more toward the setting sun, said Mr. Tong , the vice president for strategy and government affairs at Clean Power Finance, an investment firm. That way, a bigger portion of their production would come at the hours when electricity was most needed. But their total production would be a bit lower, and that would hurt panel owners, at least under current rules.

Image: North American Solar Stores.