Solar panlesThe City of St. Louis Park in Minnesota passed an ambitious Climate Action Plan in 2018 which documented the city’s goal to achieve carbon neutrality by 2040. Within the plan, the city also details a goal to achieve 100 percent renewable electricity by 2030 and supply 10 percent of building electricity consumption with rooftop solar photovoltaic (PV) by the same year. Now, St. Louis Park is working to implement its plan and undertake the necessary actions to turn goals into reality. My colleague, Abby Finis, was the lead consultant working with the city to develop their plan and Great Plains Institute staff continue to assist them with implementation.

As part of the implementation effort, a Solar Suitability Assessment Tool was created with technical assistance from GPI. The tool provides a valuable resource for St. Louis Park community members by enabling them to see the solar generation potential for every single rooftop in the city (see figure 1). The tool was modeled off a similar tool made for the City of Minneapolis–Find My Solar Suitability–which was developed by the city’s sustainability staff working with the geospatial company ESRI.

Screenshot from the St. Louis Park Solar Assessment Tool

Figure 1. Screenshot from the St. Louis Park Solar Assessment Tool

How does it work?

Using raster data for solar insolation (or solar potential) processed by the University of Minnesota’s U-Spatial team that provides high resolution (1-meter) insolation estimates, staff at GPI were able to calculate how much solar energy hits a given rooftop. These estimates were further finetuned using the slope and direction of the rooftops, as well as shading from tree canopy or nearby buildings. The output of this analysis approximates the solar resource for a given rooftop, which is shown as the variable colors of the rooftops. As shown in the tool’s legend (see figure 2), red indicates good solar insolation and blue indicates poor solar insolation for square meter cells across each rooftop. Because building footprints for the entire city were used as a proxy for rooftop identification, all rooftops were analyzed, including multifamily, large commercial, and other buildings that may present unique solar PV opportunities.

Legend of solar area potential

Figure 2. Legend of solar area potential

Who can use it?

St. Louis Park residents and business owners can go into the application, enter an address of interest, and find information about how many panels are estimated to fit on the rooftop, the area suitable for a solar installation, and the estimated generation capacity, annual production, and estimated value in electricity.

These estimates can help interested users determine whether their rooftop has good potential for a solar PV installation before scheduling an on-site assessment.

The tool can also help the city start to identify where and to what extent in-boundary rooftops could supplement the city’s energy use with renewable, carbon-free energy resources.

How does this fit into the bigger picture?

Dollars Saved

This tool comes at a pivotal time not only for St. Louis Park, but also in the world of solar energy, as 2019 marks the final year before the current 30 percent tax investment credit for solar rooftop installations drops down to 26 percent in 2020, and 22 percent in 2021 before it expires. Though the credit is one of many finance mechanisms available to a homeowner or business considering solar PV, that percentage decrease could translate to an $800 differential in tax credit dollars for a $20,000 solar PV system in 2020. This means that for many homeowners and business owners who have been on the fence about rooftop solar, now may be an optimal time to go for it.

Climate Impact

Estimates using the solar data found that if St. Louis Park were to utilize all its in-boundary rooftop solar resource, it could offset upwards of one-third of its 2016 electricity usage (which includes combined residential, commercial and industrial, as well as municipal sources). Given the potential rooftop solar generation capacity, if the top 10 buildings for rooftop solar in the city installed systems, their combined generation could potentially offset over 1.5 percent of the city’s total electricity usage (electricity data used in calculations from Xcel Energy Community Energy Reports, 2016).

There is tremendous opportunity right now to start moving the needle on solar energy generation in St. Louis Park that will have tangible impact on the climate action goals the city has set for itself.

Coordinated Outreach

Moving into 2019, through collaboration with Solar United Neighbors and St. Louis Park High School students (participating in iMatter and a local, environmental student group, Roots and Shoots) working through a Hennepin Country Green Partners grant, there will be increased education and outreach throughout the City of St. Louis Park. The outreach will focus on what it means to install rooftop solar PV, how to finance a solar installation, as well as renewable energy and electricity efficiency measures for homeowners or business-owners. Hopefully these efforts can help dispel some of the barriers to solar rooftop installation–including common misconceptions that community members “don’t have a good roof” or think that “solar is out of their price range.” The Solar Assessment tool will be an important part of that outreach by providing a free, open source way for St. Louis Park community members to start thinking about what solar potential their rooftop may have.

Listen to an interview about this effort on the Yale Climate Connections podcast by clicking below.

Explore the Solar Tool & Climate Action Plan

To view the St. Louis Park Solar Suitability Assessment Tool, visit this link:

To view the City of St. Louis Park’s Climate Action Plan:

Additional Resources

The City of Duluth, MN also has a solar suitability assessment tool which can be viewed here:

To view Uspatial’s MN Solar Suitability Assessment tool, follow this link:

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