Factors That Can Affect The Performance af Solar Panel

Having solar panels on your roof is definitely cool. If there’s any single technology related to residential energy efficiency that has an incredible wow factor, solar is it. When people think of energy efficiency, renewable energy, or alternative energy, solar is the first thing that comes to mind. All this interest and awareness about solar is great, but it also has a downside. Solar has gotten so much attention that some people think it’s the only method of having an efficient home. As I explain in my book, solar is a great way to significantly lower your electric bill, but for most people, it’s not going to completely eliminate it. The fact that solar doesn’t supply 100% of most users’ electricity has led to the misconception the technology doesn’t work.

Unless you are willing to make some major changes in how you use electricity in your home, solar is going to be a supplement to the energy you get from your utility company. My own experience is a good example. I make the point on this website and in my book that I’m not willing to give up my comfort in order to lower my utility bills.

My electrical usage is relatively high (at least for a guy in the “green” industry), but my solar array still reduces my bills by an average of 40% over the course of the entire year. In the summer, when there is more sunshine, and my air conditioner is running all the time, my electric bills are still reduced by almost 50% per month.

In one way or another, I’m always going to be tied to the utility grid. A recent development is reinforcing that point. When my wife and I moved into our house, the neighborhood was still being built. For a few years, a lot diagonally across the street from our house was vacant. Last October, construction started on a house on that lot, with the roof framing being completed in December.

By the way, the house being built isn’t just any house but a three-story one. The problem (for me) that has arisen is the lot and the house being built on it are in direct line of sight between the solar panels on my house and the rising sun. As a result, the new house is reducing the electricity produced by my solar panels by half a kilowatt per day.

Considering my solar array produced, on average, six to seven kilowatts per day during the winter months, a reduction of half a kilowatt is noticeable. My situation and how it affects my solar electric production is not that unusual.

In fact, there are a number of factors that can affect the performance of a solar array. These need to be taken into consideration before you decide to invest in solar for your home. I will outline these below.

Panel Orientation

Most residential solar panels in the United States are mounted on rooftops. The best orientation for the maximum performance of a solar array is facing directly south. Unfortunately, not all homes are built with part of the roof facing south. In these situations, an east or west orientation will work, but the solar array’s total performance will not be as good as it would be on a south-facing roof.

solar panels mounted on rooftops

It is possible to design a system to compensate for solar panels that don’t face directly south, but it doesn’t work all the time. East or west-facing solar panels will generally perform at around 80% of the capacity of ones that face directly south.

As an FYI, solar panels on a north-facing roof will not work.

Roof and Panel Pitch

The pitch or tilt of your roof can have an effect on the total number of hours of sunlight your solar panels receive on an average day throughout the year. The pitch of the roof is important due to the fact the sun is in different positions throughout the year. In the winter, when the sun is low in the sky, a steeper pitch is better, whereas the opposite is true in the summer when the sun is higher in the sky.

The “optimal” pitch for roof-mounted solar panels will vary, depending on what part of the country you live in. For most people, you’re limited to the existing pitch of your roof. There are systems available that automatically follow the sun throughout the day. These are very expensive, however, and typically not used in residential installations.

For a typical residential setting, a good technician will be able to determine if the pitch of your roof will be sufficient to make solar a viable option for your energy needs.


This one sounds odd, but it’s true. Solar panel performance can be reduced due to heat. And where does that heat come from, you may ask?

Well, from the sun….which is shining on your solar panels so they can produce electricity. The truth of the matter is solar panels get hot as they absorb sunlight.

If they get too hot, they can lose upwards of 25% of their output. The solution to this is really simple. Your solar panels should be mounted a few inches above the roof. Typically, the frames the panels are mounted on give a six-inch space between them and the roof. This allows sufficient airflow to cool the panels and maintain a good operating temperature.

Components, such as the inverters, should be mounted under the panels so they are not in direct sunlight. Pigeon screens are also a good option to help maintain proper airflow around your solar panels. These are mesh screens mounted around the system framing to keep birds and animals from building nests under the solar panels. Large nests can restrict the airflow under the panels, resulting in the system getting too hot.


This is the biggest issue affecting solar performance. It’s the one now affecting my system. The amount of shade, or the lack of it, will be a huge factor in determining whether or not your home is a good candidate for solar.

If your home is close to tall buildings, has large terrain features, or is located in an area with lots of tall trees, solar might not be the best option for your energy needs. It’s because of situations like this, even though I’m a huge fan of solar, that I take the position it’s a technology that won’t work for everyone.

If your home is located in an area where you have more shade than direct sunlight, I would hate to see you waste your money on something that won’t perform properly and will not meet your needs.


As with any energy efficiency technology, it’s important to get a full assessment of whether or not it’s the best option for you before you buy it. This is especially true with solar arrays, where you will either be financing or leasing the system for an extended period of time. A knowledgeable technician from an established and reputable solar system installation company will be able to evaluate the orientation, pitch, and shade in your area in order to determine if solar is the right choice for you.

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About the author
Ben White has written thousands of articles on everything home improvement. He has had the privilege of writing for such websites as the Huffington Post, DeWalt, Houzz.com, HGTV, and many others.

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