How to Determine the Right Solar Panel Size for Your Home


If you’re ready to take the plunge and set up a solar panel array on your home’s roof, your family is on the cusp of a brighter, more energy efficient future. Of course, the process of purchasing and installing a rooftop solar array isn’t quite as simple as buying a new backyard grill or choosing new blinds for your living room. Before you make a lasting investment in your home’s energy infrastructure, take a moment to learn how to determine the right solar panel size for your new array.

Determine Your Roof’s Orientation and Size

As with any significant purchase, it’s crucial to make adequate preparations for your new array’s installation. First, you’ll need to size up your roof to determine its theoretical capacity. In the Northern Hemisphere, solar panels must be oriented southward to maximize efficiency. As such, you’ll only be able to set up an array on the south-facing slope of your roof. If your roof is flat or has an east-west orientation, you may be able to install panels on its entire surface. However, it’s possible that such an arrangement would slightly reduce the array’s overall efficiency.

You’ll also need to measure your roof’s square footage. If you have reliable specifications for your house, you may be able to use them to arrive at an accurate figure. Otherwise, you’ll have to measure its usable surface area with a measuring tape or string. If you have to climb up on your roof, be sure to take adequate safety precautions. While you’re up there, you can strengthen your calculations even further by measuring the surface’s precise slope.

Lock Down Your Average Monthly Power Consumption

You don’t have to read your own power meter or perform complex arithmetical calculations to figure out the amount of power that your home consumes in a typical month. Simply look over your utility bills from the past several billing cycles and take the average of each month’s kilowatt-hour usage. If you don’t have these bills on hand, you might be able to find comparable information online or through your utility’s phone hotline.

Choose the Right Material

Although all solar panels are highly efficient, some materials are “better” than others. While the differences are too fine for an in-depth review, it’s important to know that there are three basic types of photovoltaic material: amorphous crystalline, polycrystalline and monocrystalline. Although amorphous crystalline panels tend to be less expensive than monocrystalline arrangements, they require more space to generate the same amount of power. This highlights the importance of determining your home’s power needs before settling on specific panel sizes and types. If your efficient home can generate all of its power with a less-expensive amorphous crystalline array, you may be able to reduce your start-up costs without adding to your monthly utility bills.

Leave Room for Aesthetic and Practical Considerations

Once you’ve settled on a material, you’ll need to calculate the minimum size of each panel that you place on your roof. Several practical considerations will come into play here. First, determine whether any preexisting obstructions will reduce your panels’ efficiency. Such obstructions might include steep hills, tall trees or buildings. If any of these are present, you’ll need to factor them into your calculations and increase your array’s size proportionally.

Finally, don’t neglect aesthetic concerns. For instance, ask yourself whether it makes sense to cover every square inch of your roof with solar panels. You might not have the final say in this matter–if you’re a member of a homeowners association, any improvements that you make to your property could be subject to certain aesthetic guidelines or restrictions. No matter how it turns out, you’re sure to reap the financial and ecological rewards of your decision to install rooftop solar panels on your home.

Article by Steve Wright who works for Whirlwind Steel Buildings, Inc. They design and manufacture steel riding arenas featuring low maintenance, ease of expansion and a variety of colors.

About Author

Walter’s contributions to CleanTechies over the past 4 years have been instrumental in growing the publications social media channels via his ongoing editorial and data driven strategies. He is the founder and managing director of Sunflower Tax, a renewable energy tax and finance consultancy based in San Diego, California. Active in the San Diego clean technology community, participating in events sponsored by CleanTech San Diego, EcoTopics, and Cleantech Open San Diego, Walter has also been a presenter at numerous California Center for Sustainability (CCSE) programs. He currently serves as an adjunct professor at the University of San Diego School of Law where he teaches a course on energy taxation and policy.

1 Comment

  1. douglas prince on

    Let’s not also forget about the weight aspect. Make sure roofing frames and any crossbeams are reliable enough to handle the additional weight. This is especially important if you also consider a solar water heating system.