Solar rooftop potential refers to the total technical capacity for solar power generation, expressed in terms of energy output. This potential is determined by factors such as roof size, orientation, shading, and geographical location. Rooftop potential doesn’t consider availability or cost. Rather, it is the technical limit of potential solar energy production on existing rooftops across the country.
Satellite maps, irradiance data, equipment specifications, and other factors inform the bids that installers present to customers to assist them in understanding the potential costs and benefits of solar panels on their roof.
National Rooftop Potential
According to the study Rooftop Photovoltaic Technical Potential in the United States by the National Laboratory of the Rockies (NLR), there are over 8 billion square meters of rooftops on which solar panels could be installed in the United States, representing more than 1 terawatt of potential solar capacity. With improvements in solar conversion efficiency, U.S. rooftop potential could be even greater. Residential and other small rooftops represent about 65% of the national rooftop potential, and 42% of residential rooftops are households with low-to-moderate income.
In its Cost-Reduction Roadmap for Residential Solar Photovoltaics (PV), 2017-2030, NLR estimates that an average of 3.3 million homes per year will be built or will require roof replacement—representing a potential of roughly 30 gigawatts (GW) of solar capacity per year. If even a small fraction of these new roofs had solar installations, it could have a significant impact on U.S. solar power generation.
Individual Rooftop Potential
National laboratories and private companies have developed several tools to estimate solar rooftop potential. The tools described below were funded in part by the U.S. Department of Energy (DOE) Integrated Energy Systems Office (IESO) to help consumers determine the solar potential of their homes or businesses.
EnergySage
EnergySage, a previous Incubator Program awardee, allows homeowners, businesses, and nonprofit organizations to estimate their energy savings from solar power, and connects them with prescreened installers who can provide project-specific estimates. Users can select the system that best fits their needs. Electricity bills are used to estimate the potential savings from solar energy, and EnergySage may offer substantial savings over more conventional products.
Google’s Project Sunroof
Google’s Project Sunroof is a solar calculator tool that uses multiple data sources to determine how much a home would benefit from a rooftop solar installation. When homeowners enter an address, Project Sunroof looks up the building in Google Maps and combines that information with other databases to create a personalized roof analysis. The Project Sunroof website also offers a data explorer, which allows visitors to see aggregated data and cost estimates for different areas of the United States and Puerto Rico.
PVWatts
PVWatts is an online tool from NLR that estimates the energy production and cost of electricity for grid-connected PV systems throughout the world. It allows homeowners, business owners, and nonprofit organizations to easily develop performance estimates of PV installations based on maps or user supplied data.
Other Tools
Distributed Generation Market Demand Model
The Distributed Generation Market Demand (dGen) Model simulates customer adoption of distributed energy resources for residential, commercial, and industrial entities in the United States and other countries through 2050. It can analyze the key factors that affect market demand for distributed energy resources.
National Solar Radiation Database
The National Solar Radiation Database (NSRDB) provides a complete collection of hourly and half-hourly values of meteorological data as well as the three most common measurements of solar radiation: global horizontal, direct normal, and diffuse horizontal irradiance.
PV Rooftop Database
NLR's PV Rooftop Database shows which buildings in 128 U.S. cities have the technical potential for solar panels. Using laser scans, it pinpoints suitable rooftops and estimates how much solar power each could produce. The data is organized by city and when the scans were taken. For each city, you can find maps showing: 1) the area scanned, 2) the buildings, 3) the flat parts of rooftops good for panels, 4) the direction those roof parts face, and 5) how much solar power they could produce.
PV_LIB Toolbox
The PV_LIB Toolbox is an open-source software package that allows users to simulate the performance of photovoltaic energy systems. There are two different versions—for python and Matlab—that have grown significantly from user contributions.
PVsyst
PVsyst allows customers to utilize advanced simulation tools to model photovoltaic systems and calculate their profitability. Customers also have access to extensive support via email, forums, frequently asked questions, and tutorials.
REopt
The REopt platform recommends the optimal mix of energy, conventional generation, and energy storage technologies to meet cost savings, resilience, and energy performance goals.
System Advisory Model
The System Advisory Model (SAM) is a free, techno-economic software model that enables technical performance simulation and financial analysis of energy projects. SAM combines weather data and system specs to calculate potential electricity production. It uses system cost, compensation, financing, and incentive data to calculate levelized cost of energy, net present value, payback period, internal rate of return, and revenue of a potential project.
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