✅ What Affects Solar Project Viability?

15 min

There are many factors that can affect a solar project. The property type, roof type and the age of the roof, roof plane orientation, roof shading, the home’s electrical system condition, and availability of capacity on the local utility companies grid unit can all impact whether or not solar can be installed on a property.

House types

Property Type

The most ideal candidates for solar are single family one or two story detached houses owned by a single occupant or a married couple. This is preferred as the homeowners have full authority to make the decision.

In most cases, we work with single family homeowners. Depending on the market we can also assist 2-family or multi-family homes. We can also service some townhouses and modular homes.

EnergyPal does not service commercial properties, office buildings, or condo towers as the interconnection requirements, customer profile, and energy management systems are very different.

How Roof Types & Age Impact Home Solar

There are many different roof types throughout North America.

Solar requires a viable roofing solution which will last! This means we need to assess older roof materials to ensure there won’t be any leaking over time. When homeowners have roofs that need to be replaced we can almost always couple a solar project with a re-roof for a homeowner which can be advantageous due to tax incentives available.

Analysis of a roof structure, age, and material is important to ensure a safe solar installation. Solar mounting systems will drill and secure through the roof Rafters or the long beams running from the peak or ridge of a roof to the eaves or gutter. The solar racking systems are perpendicular to the rafter direction.

Composition/Asphalt Shingle


Concrete Tile-Standard Weight


Clay Tile


Flat-Rolled Composition/Modified Bitumen


Flat-Rubber Membrane/EPDM




Tar and Gravel


Metal-Standing Seam






Wood Shake




Ground Mount


Roof Plane Orientation

Where we place panels on a house makes a big difference.

When we install a solar PV system on someone’s house, we are installing generating capacity, or the ability to generate energy from the sun. This is measured in kilowatts. At the end of the day what matters most to homeowners is the actual kilowatt-hours which requires hours of sunlight to create.

The physical orientation of the panels is one of the most important factors to determine the number of hours each solar panel will be hit with. Typically we want to install on south, southwest, southeast, west, and east roof areas in that order. We may choose to put panels on the west side due to specific rate plans which have an “afternoon peak” so the panels generate more energy when it’s most expensive.

Roof Shading

Roof shading

Typically trees that are located South and Southwest of a home cast the most shade and trees on the north side of a house cause virtually no shade on a roof. Understanding how much shade is on different roof areas is critical to modeling solar savings. One kilowatt of solar panels being hit with one hour of sunlight would generate one kilowatt-hour of energy. If that same system was shaded for an hour, there would be much less energy produced. Less energy produced means more power purchased through the utility company and lower savings. Identifying impacting trees can help provide a better design and savings recommendation to a homeowner. Understanding shading impacts is typically done through 3D modeling software using our expert Design Team.

Roof Size

Satalite image of roof

In general we have a 6-8 solar panel minimum for an installation. This minimum requirement can vary and is based on roof space, technical limitations like inverters and installer job size minimums. Some roofs have a lot of areas but due to obstructions there is no easy way to install the panel minimum. Working with an EnergyPal Advisor that knows panel sizes and installation methods can help you better design a workable solar project!

Roof Obstructions

Roof Obstructions

There are many roof obstructions like vent pipes, dryer vents, skylights, chimneys, and even roof gables. Sometimes we are able to move or relocate these vents but generally we have to build around..

Geography and Climate

Depending on where the location is geographically — and the orientation and exposure of the particular house or business — you get more or less usable sunshine. Even within small, localized regions, weather patterns vary due to topography and landscape details like trees and ponds. So two identical solar systems separated by a few miles but otherwise built and operated identically may yield different energy outputs averaged over a period of time.

Here we will show you the factors that allow you to optimize the orientation and location of your solar systems. This information can assist in making important decisions, such as which type of system will work best, how big a system is necessary and how much production they can expect to achieve.

Weather is a daily phenomenon, but climate is a description of the general weather patterns over a long period of time. The weather may be cold and rainy in Los Angeles today, but the climate is warm and temperate. Our designers assess climate particulars to enhance system performance. Climate includes elements such as temperature, precipitation, and wind speed. Here's a look at how climate can affect your solar system:

Sunlight accross the USA in Spring and SummerSunlight accross the USA in Fall and Winter


Climate dictates how much sunlight we can expect annually. The map below shows the average number of hours per day of sunshine in the United States. That the Southwest gets the most sunshine per day — and that Canada and the northern states get the least — should come as no surprise. The sun is higher in the sky in the southern states so the days are longer.


We want to locate panels so they avoid being inundated with heavy layers of snow. Some locations on your roof will experience very shallow snow buildups as compared to other parts of your roof while some parts of your roof may be warmer than others due to proximity to heaters, exhausts, chimneys, and so on.

Cloud cover

If you are a homeowner living in a cloudy region, you still have solar energy and it’s generally diffused (spread out). As a result collector panel orientation isn’t so critical because light will be coming in at many different angles rather than just directly overhead from the sun.


Air pollution and smog affect the amount of sunlight they can expect to receive. If you live in an area with heavy air pollution, you can expect less system output over an extended period of time.

Air density

Homeowners get better solar exposure in the mountains than near sea level simply because the air is thinner and scatters less sunlight. You can make an approximate estimate of how clear the air is by simply observing how blue the sky is on a clear day. Thick air scatters more red light, and so the appearance of the sky is less blue and more white.


With PV systems (but not solar water heaters), the lower the temperature the happier the semiconductors, and the greater the output. Homeowners can get more system output on a cold, clear day than on a sunny day.

Frequent fog

If you are living in an area that's foggy and misty in the morning (in the San Francisco Bay Area, for example) but the mist burns off into a clear sky by noon you want to orient your solar panels more westward to optimize the amount of sunlight they can achieve over the course of a day.


Wind can tear equipment off of its mounting hardware and result in expensive repairs, not to mention dangerous conditions. If you are in a windy climate you need to make sure that you specify stronger mounting equipment. Our systems are all engineered to factor this in. Wind will also cool solar panels down and cooler panels are more efficient.

Chat with a Energy Advisor to find the right solution for you and your home:

Get a custom home solar quote.

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