Can I face my home solar panels east?

If you only have an east-facing roof that gets good sunshine, should you still go solar?

Photo of a nice house with solar panels.

To generate the maximum electricity from your solar panels, you want them pointed south (if you live in Northern Hemisphere), but sometimes you don’t have much of a choice.

Most homeowners mount their solar panels on their roof and consequently only have a couple orientations to choose from. (This is also known as azimuth, where 0° means pointing north and 180° is south.)

Solar panels will work if you face them east: on average, east-facing solar panels will generate about 80% as much electricity as they would if pointed directly south. While that reduction in power generation isn’t ideal, for many households it’ll still be good enough that they’ll see a financial payback in a reasonable amount of time.

That’s good news, but your exact power generation will vary depending on your position on earth and your roof slope. To do your own comparison between east, south, or west-facing panels, you can use our calculator and plug in different values for the azimuth (direction) of your solar panels.

However, this all depends on having net metering. If you don’t have net metering, but instead have a solar compensation scheme with your utility company that does not pay the full retail rate for solar electricity sent into the grid, then east-facing solar panels might not work very well for you.

Time-of-use (TOU) billing plans will also impact the viability of east-facing panels.

Terms to know: solar panel tilt and azimuth

Before we get into the details, there’s a couple related terms you might come across: tilt and azimuth.

Tilt is the angle of the panel relative to horizontal, where laying flat is 0° and standing straight up is 90°. The ideal tilt is perpendicular to the sun, but it matters less than you might think. This is because the entire sky is source of light, not just the sun as a point in the sky. If your solar panels don’t have the ideal tilt, it’s probably fine.

Azimuth is the direction relative to north, where 0° is pointed directly north, 90° is east, 180° is south, and 270° is west.

Why is to good to point your solar panels south?

If you live in the Northern Hemisphere, like those of us in the United States, the sun rises somewhere in the eastern sky, sets toward the west, and spends all of that time in the southern half of the sky.

It’s for this reason that when you have fixed placement solar panels - like when you have panels attached to your roof - pointing them directly south will yield the most electricity generation. That’s where the sun is.

(Fixed placement means racking that doesn’t move. While systems that slowly move your solar panels to track the sun throughout the day do exist, they are generally too expensive for homeowners.)

The situation is different in the southern hemisphere. If you live in Australia, the sun is in the northern half of the sky, and so Australians point their solar panels north.

The importance of net metering for east-facing solar setups

Net metering is a policy for solar homeowners where you get billed according to your net electricity usage. You can read our guide to net metering to learn more, but here’s a quick explanation.

Let’s say that your solar panels generated 500 kWh of electricity in one month, but your home used 501 kWh of electricity. Under net metering, you will be billed for 1 kWh of electricity, because that’s the net amount of electricity that you used. It wouldn’t matter if your house was actually consuming grid electricity or solar electricity at the time of usage. Under net metering, it’s all the same. Only your net usage matters.

This changes if you don’t have net metering. There are different schemes that utility companies use, such as net billing and feed-in tariffs, but with all of them it matters when you generate solar electricity and when your house consumes it.

Under net billing, for example, if you generate more electricity than your house is using at a given time, the extra solar electricity is sent into the grid where it gets used by your neighbors. The utility company compensates you for that, but at less than the retail rate of electricity. (The “retail rate” is what you pay for electricity - about 13 cents per kWh is the average in the US.)

How much less? It varies, but utilities will often pay you less than half the retail rate for solar electricity that you contribute back to the grid.

Why east-facing panels without net metering is a bad situation

This means that without net metering, the solar homeowner needs to try to use as much of their own solar electricity and as little grid electricity as possible. This is because any extra solar electricity, from the financial point of view of the homeowner, is largely wasted (although the utility company still benefits greatly).

If you have a house with solar panels facing east, you will start generating electricity as soon as the sun rises. Nice! A solar powered breakfast! Solar coffee! Solar toast!

But then, in most homes, people head off to work and school. With nobody home, electricity usage drops off. Because it’s early in the day, your house hasn’t had a chance to heat up, so the air conditioner isn’t running. Maybe you started the dishwasher and clothes washer before you left the house, but they don’t use very much power.

If it’s a hot summer day, by early to mid-afternoon your house will start to get warm, and the air conditioner might kick in. Unfortunately, the sun is now in the western sky, but your solar panels are pointed east.

They will still generate some power from direct sunlight and indirect sunlight reflected from the sky and clouds, but less than if they were pointed south or west.

Finally, in the early evening, you arrive home. The sun is further in the west, so your east panels are now generating even less power. The exterior walls of your house have been heating up all day, so your air conditioner is running nearly non-stop and will continue to do so for the rest of the evening. Time to make dinner, so now all of your kitchen appliances are cooking away, and using lots of power.

Time shifting your appliance use can help a little

Not everybody works from 9 to 5, so your usage pattern might be different. Maybe you’re home in the morning, and start work in the afternoon.

But even that’s the case, that may not make a big difference to your electricity usage. Appliances that people actively use while at home like dishwashers, clothes washers, televisions, and computers don’t use that much electricity. You can time-shift some of this usage by using delay-start features, but that will have a relatively small impact.

If you have an electric cooktop, that does use a fair amount of power. But for many people who decide to go solar, air conditioning is their biggest electricity hog.

Solar power and air conditioners

Unfortunately, with air conditioning usage, while you can time-shift your energy usage to some degree, it’s hard to avoid late afternoon and evening AC usage.

This is because buildings heat up and cool down according to the sun. In the morning, your house is cool. As the sun rises, the exterior of the building will slowly start to heat up, but because the wood and drywall of your exterior walls takes time to heat up, and insulation provides a barrier, the inside of your home will stay cool for a few more hours.

By noon on a hot summer day, however, the heat has started to soak through the walls. Also, unless you’ve kept your blinds tightly shut, the sun has been shining through your windows. Depending on how good your insulation is, your air conditioner might start kicking in around now.

If you have east-facing solar panels, they will provide some of the energy needed for your midday AC use, but they’re already no longer in an optimal position.

By late afternoon and early evening, the sun is starting to go down, but the outside air temperature is now really high, and the walls and roof of your house have been baking all day. Your AC might be running full time now.

If you have a smart thermostat, you can shift this AC usage somewhat by precooling your house in the morning, but unless you have a super energy-efficient house, you won’t avoid running your AC late in the day and into the evening.

AC is a big reason why it makes the most sense to face your solar panels west in hot climates.

Another caveat: time-of-use plans

If you live in California, new solar homeowners are required to have a time-of-use (TOU) plan. TOU with solar means that electricity you generate late in the day during peak hours when utility rates are high is more valuable than off-peak hours when electricity is cheaper.

This means that you will often want your solar panels facing southwest or west. East panels that generate electricity during the off-peak hours of the morning will be much less valuable.

To learn more about California net metering and how time-of-use works, read our guide to TOU solar plans.

Ground mounts are an alternative to east-facing solar panels

If you’re stuck with an east-facing roof as your best option for solar panels, one alternative to consider is a ground-mounted array.

Ground mounts require enough clear yard space that won’t receive significant shading during the day. For most homeowners, a fixed ground mount that doesn’t move to track the sun makes the most economical sense.

While the initial cost of a ground mount is usually quite a bit higher than a rooftop system, it does give you more freedom to place your panels and will let you choose the best orientation.

They require a good foundation and often a geotechnical review because a solar array is quite heavy. Less than 5% of residential installations use ground mounts, but can make sense especially if you live in a rural area.

Conclusion: east-facing solar can work for some people

You can’t just rotate your house so that it faces the best direction, nor can you just chop down your neighbors trees that are shading your roof. If you only have an east-facing roof that is sunny and unshaded, should you still go solar?

Yes you can, if you have net metering and aren’t required to have a time-of-use billing plan. New California solar customers are required to have TOU, so east-facing solar panels generally won’t work for you if you live in California.

But that still leaves many parts of the country where you can have a perfectly viable solar system mounted on an eastern roof.

To get a quick estimate of your power generation, use The Solar Nerd calculator and plug in the details about your roof. You can see how many solar panels you’ll need to meet your energy needs.

For a more accurate assessment, work with a professional solar installer. They’ll provide a detailed technical analysis that will break down how your east-facing roof will perform.

TAGS:
#Azimuth #TOU #System Design

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