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How Much Rooftop Solar can Potentially be Installed In the United States?

In a report from the National Renewable Energy Laboratory (NREL) published this past month, the total potential for rooftop solar in the U.S. could potentially account for at least 38.6% of total U.S. electricity creation. This does not include ground mounts, canopy, building facade, or any other type of solar installation. This is just purely a quantified estimate of solar that can be installed on small, medium, and large building rooftops for a total installed capacity of 1,118 GW. Currently the total installed solar capacity in the U.S. is 27 GW.

The previous estimate by the NREL was 664 GW of installed capacity in a study conducted in 2008. So this new survey nearly doubles their previous estimate. The report looked at small, medium, and large buildings to determine to what extent each category could contribute to supporting solar. The biggest takeaway? 83% of all small buildings have a suitable location for solar installation. The large potential of small buildings is 65.4% of the total rooftop market (731 GW). If the residential market for solar reaches its potential, it could account for 25% of the total US electricity generation.

Why is it so important? For one thing, the estimated market is far larger than originally thought. Solar is nowhere close to being a mature industry and this study shows that there is a lot more room for solar to grow than previously thought. Consider that solar installation prices have dropped 70% since 2010 while 85% of all solar has been installed in the past five years. Solar is around 1% of total electrical generation in the country. Coal (33%), natural gas (33%), and nuclear power (20%) make up 86% of total electrical generation. In order to meet the RPS standards in states around the country, reduce carbon emissions, and ensure economically stable energy prices, the installation of solar is a national priority.

How did the NREL come up with these numbers? To simplify matters, they used light detection data, geographic information system methods, and PV-generation modeling on 128 cities nationwide to find out how much space on rooftops solar could be distributed. Then they extrapolated the results based on this data for the rest of the country. The factors affecting rooftops were

  • shading (potential of panels to be blocked by obstructions such as trees or mountains)
  • roof tilt (is the roof too steep and therefore not at an appropriate angle to support solar)
  • azimuth (north-facing roof sections were mostly discounted)

What does it mean for states that Yellowlite does business in, particularly our home state of Ohio? What is the market for the top states? Well, Ohio has the fourth largest market potential and our neighboring states of New York, Pennsylvania, and Michigan round out the top seven:

 

State

Annual Generation Potential % of sales

Installed Capacity Potential(GW)

Annual Generation Potential (tWh/year)

Total Roof Area (millions of meters^2)

1

California

74.2%

128.9

194

961

2

Texas

34.6%

97.8

131.2

715

3

Florida

46.5%

76.2

103.2

557

4

Ohio

35.3%

46.8

53

338

5

New York

37.4%

46.6

55.3

340

6

Pennsylvania

34.5%

43.6

50.4

316

7

Michigan

45.9%

42.1

47.3

303

 

 As of 2015, there was 113 MW of cumulative installed solar in the state of Ohio. This means that Ohio has installed 0.24% total solar (including ground arrays, etc.) of the capacity that rooftop solar currently offers by itself (46.8 GW). If the solar industry continues to grow at its rapid pace, it would still take decades for solar to make a dent in the potential capacity. In the future, we might see new buildings be constructed with solar in mind, including having a north-south orientation to ensure solar is able to be accommodated. In short, solar panels for your home are going to become a common occurrence.  

Further Room for Optimism

The survey does not take into consideration ground mounted arrays, mounting canopies (especially over parking lots, an increasingly common practice) or the future integration of thin film or amorphous PV into building facades or even windows.  Ground mounted arrays, particularly utility-scale installations in the Southwest (some of which are as large as 550 MW) and also those in the heartland (an example of which is the 4.3 MW system in the community of Minster) are not part of this survey. There has not been a survey estimating how much solar could be installed because the potential includes most of the land of the earth since a ground mounted array can be constructed nearly anywhere.

The survey also does not take into consideration installations on less suitable roof area (which YellowLite sales staff would require a great deal of consultation with a customer on) which includes areas that may be prone to more shading, facing north, or at a pitch angle on the roof that might not be acceptable. These sections would receive sunlight and generate electricity, but they would not be quite as economically viable as residential solar panels on roof space that is more south-facing and at a better angle to receive the sunlight. 

The 38.6% estimate is based on an average solar module efficiency of 16%. If premium modules with 20% efficiency were installed, the estimates would be increased by 25%, meaning that solar installed on the same buildings with higher efficiency panels could push the potential of solar to 48.2% of all U.S. electricity generation just by rooftop arrays. If ground mounted arrays, parking lot canopies, and building-integrated PV were combined together, there could be the potential to generate well over half of all U.S. electricity needs. Obviously, it would take a tremendous amount of construction, effort, and funding to make that occur. But it is now a distinct possibility. 

Solar panels for your house or business not only save you money on your electricity bill, add equity to your house, and help save the environment, they also help you achieve greater energy independence. We encourage customers to do their due diligence and look into the best solar panels and the most efficient solar panels instead of just cheap solar panels. Solar panel costs, especially for a solar power system had dropped precipitously. Now is the best time to go solar.  

 


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