Pointing them at the sun gets you most of the way. Here are the finer details.
"What's your angle?" may be the go-to question for the cynical and suspicious, but when it comes to solar panels, it's an essential query.
Along with the direction solar panels face, angle plays an important role in their efficiency in turning the sun's energy into electricity. As the sun moves from the east to the west over the course of the day, the angle of solar panels will determine when they collect the most power.
With that said, with most residential solar projects the angle of panels will be determined by the pitch of a home's roof.
"If your home has a pitched roof, you typically want the panels to be flush to the roof," said Tom McCalmont, CEO of Paired Power. "It's usually not to any benefit to tilt."
Photovoltaic solar panels work by absorbing sunlight to create electrical charges, which can be turned into electricity. This all starts with the panels collecting solar radiation. This comes primarily from the sun directly, but can also come from sunlight reflected from surrounding areas.
Because the primary source of solar radiation will be direct sunlight, your solar panels' orientation will affect how much energy they'll make and when.
Your home's roof will typically face two directions. Ideally for solar power, one of those directions should be south (in the northern hemisphere) to face the equator, which receives more sun than the rest of the planet. Having a roof that doesn't face south won't disqualify you home from enjoying the benefits of solar, but you may need additional panels to compensate for any inefficiencies.
For nonresidential solar projects that offer leeway for panel placement, there are a few factors to consider.
"It depends what you're trying to optimize," McCalmont said. "You can pick an angle that will optimize the energy value that you collect over a year, or you can pick an angle that optimizes the economic value. In the winter, the sun is down here, and in the summer, the sun is up here. If you're trying to optimize the energy yield over the course of the year, you want to pick an angle that's kind of the midpoint of those two extremes."
The Earth's equator, the line that splits the planet between the northern and southern hemispheres, gets the most direct sunlight year-round. Therefore, "In the northern hemisphere, it's optimal for your solar panels to be facing south," said Gilbert Michaud, assistant professor at Loyola University Chicago's School of Environmental Sustainability. "This offers the best sun exposure throughout the course of a day, meaning that you'll generate more electricity compared to facing any other direction."
The reverse is true if you live in the southern hemisphere; you should orient your solar panels facing north so they will be exposed to sunlight all throughout the year.
Of course, not all global northerners' roofs face south, which is OK. Solar panels can still collect the sun's photons when facing other directions, just not as much as when facing south.
"There has also been a movement to face panels west, as their output will better match peak electricity demand in the evenings" Michaud said.
West-facing panels have been found to reduce a home's reliance on the grid during peak hours more than south-facing alternatives. Nearly 25% of all solar installations in 2021 were oriented west, according to the Lawrence Berkeley National Laboratory (PDF), likely in order to generate more energy later in the day.
Angle also affects solar panel production. Optimally, sunlight would hit your panels perpendicularly, which results in the highest level of solar production. The angle of the panels can sometimes be modified during installation, though installing panels flush is most common.
There are two critical factors when it comes to the best angle for solar panels: what season it is and where you live. Joshua M. Pearce, a materials engineer who researches solar power systems at Western University in London, Ontario, recommends using this tool from Solmetric that recommends the ideal angle based on where you are. Typically, that's between 30 to 45 degrees, though it should be lower in the summer and steeper in the winter.
"It is a quick simulation that will show the best tilt angle and direction to face your solar system, assuming it does not move," he said. "As a general rule, if you live in a snowy environment you will want to err on the high tilt angle to reduce snow losses and take advantage of high snow albedo (the fraction of light that a surface reflects)."
Some in the solar industry recommend using latitude as a means to determine the best angle, but McCalmont said that most people can ignore it: "Optimize for land costs or roof costs: how much space do you have available? How much energy are you trying to pack into that space? What are the differential costs from summer and winter utility rates?"
As mentioned above, residential solar panels are usually installed to be flush with the roof. For other types of projects, including commercial rooftop solar or a ground-based solar farm, panels can be fitted with trackers, which allow the panels to "follow" the sun to boost efficiency over the course of the day.
"The reason that makes sense on a large commercial field is they can power that tracker with one motor that might control hundreds of panels, so the energy lost by powering that motor and the cost of that motor end up being pretty small in comparison to the energy from doing tracking," McCalmont said. So essentially, it wouldn't make sense for a small-scale residential project, not to mention most residential panels aren't installed to tilt.
There may be an instance where a homeowner may have a ground-based system -- such as a prepper or someone who lives off the grid. In those cases, they may want to consider adjustable racks that allow the panel angle to be tweaked. Pearce is the co-creator of an open-source wood-based rack, the design of which is available here.
"Angle tends to be pretty straightforward to optimize for that economic value," McCalmont said. "But direction is a little more challenging to do because it depends on the shape of your land, the shape of your building and the shape of your house."
Any reputable solar company should do simulations of how much sunlight your property should receive in a year, as well as conduct a sight survey to ensure your roof is not shaded by trees and receives enough sunlight for your energy needs.
"There are companies that will sell you anything, even if your roof is completely shaded," McCalmont said. "You want a company who's ethical and understands these factors."