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Best Direction for Solar Panels
Here's how to maximize your efficiency
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Overview
In most cases, the best direction for solar panels is facing south1. Arrays that are appropriately oriented can improve energy output by up to 30% or more2. However, factors such as roof slope and proximity to the equator may have some homeowners considering other directions (including north).
So how do you know which direction your solar panels should face? In this article, we break down the best direction for any goal and the aspects that influence that decision. We even offer solutions if south facing solar panels aren’t an option. Read on to learn more.
Why does solar panel placement matter?
Before learning how to position an array, you may wonder why the position has any effect at all. So long as you point your solar panels toward the sun, they’ll produce energy, right?
That’s partially true, but with an understanding of how the equipment works, you can generate even more energy. For maximum efficiency, solar panels need to face directly at the sun.
Within every panel exists several photovoltaic (PV) cells (units that absorb sunlight)4. They’re made of a semiconductor material that takes in specific wavelengths of light, called a bandgap. In fact, studies show that modern silicon cells can only take in 33% of the energy that hits them3.
Because this bandgap is so picky about what waves it absorbs, the PV cells need the sunlight to come right at them. With even the slightest turn away from the sun, these cells start to reflect wavelengths away instead of absorbing them in.
When your solar panels only have access to a small amount of energy, it’s worth your investment to point them in the right direction. This simple adjustment, along with the ideal angle, can increase your solar array’s efficiency by a considerable amount.
Best direction for solar panels
If you live in North America, the best direction for solar panels is facing south1. Situated north of the equator (which puts the sun on the south side of houses), homeowners have the best opportunity to cover their power usage, top off batteries, and maximize offsets from net metering.
However, others may find reasons to face their array in different directions. Let’s learn about the best solar panel orientation for any goal.
South facing solar panels
Our understanding of why south is the best direction for solar panels in the United States starts with the equator.
This is the imaginary line that separates the earth into two hemispheres: northern (where the US is located) and southern. It’s also the center of the range where the sun sits in the sky. So during the equinox, you’ll find it directly overhead at noon on the equator line.
What does that mean for the U.S.? Everything north of the equator line will find the sun facing slightly south.
To take advantage of this knowledge, you can point your solar panels southward. This gives them the best opportunity to absorb energy, powering your home and charging your batteries.
However, this isn’t where the benefits end for south facing solar arrays. If you live in a state that offers net metering, you can connect your system to the power grid and earn credits toward your monthly electricity bill.
West facing solar panels
As PV arrays begin orienting away from the south, they immediately become less efficient. In fact, west facing solar panels produce an average of 15% less electricity2.
However, those that pay for electricity via Time-of-Use (TOU) pricing plans can benefit from the change in direction.
TOU plans charge customers for power on a scale based on peak usage. They’re typically highest in the evening, when homeowners return from work. With panels facing southwest or true west, your array creates more energy when electricity is at its highest rates.
Which states use a TOU pricing plan?
States that utilize a TOU pricing plan include5:
California
Arizona
Maryland
Delaware
Oklahoma
Texas
Ohio
Arkansas
Louisiana
New York
East facing solar panels
Much like west facing panels, arrays oriented to the east create about 15% less energy than average. Therefore, you should only consider this as an option if you don’t have a southside roof available2.
North facing solar panels
The complete opposite of south facing panels, arrays oriented to the north provide nearly 30% less power2, making them the least ideal. If you live in the continental U.S., you’ll opt for this direction if it’s your only option.
However, if you live in Hawaii or Puerto Rico, it’s a slightly different story.
The sun doesn’t stay on the equator line throughout the year; depending on the season, it moves up and down the latitudes (more on this below). During the summer solstice in June, it’s as much as 23.4 degrees north from where it started during the equinox.
This is important knowledge for Hawaiians and Puerto Ricans, who live at 19.9 and 18.2 degrees north, respectively.
During the summer, when the sun spends more time overhead than any other time of the year, it’s actually on the north side of homes. This means if you live in Honolulu or San Juan, it may be viable to have north facing solar panels.
Directional factors for solar panel output
Distance from south
For the average American homeowner, you’ll receive the most out of an array by pointing your solar panels south. Any direction away from south outputs decreasingly less energy. Generally, you can expect efficiencies to drop by 15% for every 90 degrees2:
Southwest or southeast: 8% less efficient
West or east: 15% less efficient
North: 30% less efficient
Sources
1. Energy Education CA
2. Solar Power World Online
3. ph.qmul.ac.uk
4. Energy.gov
5. sdgenews.com
To present these guidelines, we examined a range of efficiencies from this Folsom Labs report and established a general measurement. For deeper insights into the effects of direction on solar panel efficiency, check out their article.