Recently, Sol Systems published a piece on D.C.’s solar density that places the District ahead of all other states, with an impressive 65.5 kW/mi2 of solar.  However, the true test for D.C. – which admittedly has more in common with a city than a state – is how it stacks up against leading solar cities in solar per square mile. This analysis relies on data from PJM-GATS, the California Solar Initiative, and the NREL Open PV Project, and uses data for counties when city-level data is unavailable or when the city and county perimeters are approximately identical.

Unfortunately, the nation’s capital loses its commanding lead when pitted against top cities.  California cities and New Jersey counties significantly exceed D.C. in solar density.  Data from the California Solar Initiative revealed that every California city analyzed – except, interestingly, Los Angeles – exceeds D.C.’s solar density, with a high in Bakersfield, CA of 325 kW/mi2.  Solar centers San Diego, Berkeley, and San Francisco also outranked D.C.

At least three New Jersey counties outrank D.C., with Hudson County maintaining an undeniable lead over all other cities at 336 kW/mi2.  Since the tighter footprint of cities tends to produce higher densities than counties, New Jersey’s dominance is especially noteworthy.  In terms of area, that quantity of solar currently covers somewhere around 0.1% of the county. However, with the exception of New Jersey, D.C. still exceeded all city hotspots in other SREC states.

Surprise contender Gainesville, Florida is the only other East Coast city to challenge D.C., boasting over 80 kW/mi2.  The beneficiary of a strong feed-in tariff, Gainesville now has close to 4MW installed – more than the state of Indiana and slightly less than Michigan. Los Angeles may see the next big jump in installed solar – recently, Los Angeles became the largest city in the U.S. with a feed-in tariff.  It will bring at least 75 MW on line by 2016, with an option for up to 150MW.  As the L.A. program ramps up, we can expect to see the city move up in the rankings. Generally, patterns of commercial solar development all across the United States also reveal the importance of strong incentives in catalyzing good solar projects.

Speaking of strong incentives, the aggressive solar carve-out in the D.C. Renewables Portfolio Standard will drastically expand solar in the District through 2023.  What will solar density in D.C. look like at the conclusion of this massive push?  In the year 2023, D.C. is required to supply 2.5% of its energy from solar sourced within the District.  Based on projected energy use in that year as determined by 2008 Energy Information Administration (EIA) data on retail electricity usage, the final total will be 332 MW in 2023.  In terms of density, that comes to a whopping 5,407 kW/mi2.  Even if we reach just 80% compliance, that figure is still 4,326 kW/mi2 – nearly thirteen times more concentrated than density leader Hudson County, NJ.  Of course other cities will continue to increase their solar density well into the future, especially where strong incentives are in play – but in a future where all rooftops have solar, everyone wins.

A note on the data: Installed capacity data was taken from the NREL OpenPV Project, California Solar Initiative and from PJM-EIS GATS reporting. The NREL OpenPV Project relies on open-source data and user contributions to form its database. This data is tentative and imperfect, but still proves useful as a ranking mechanism. Until accurate 2011 data is compiled and released for further analysis, we look to this comparison as a strong indicator of D.C.’s strength as a solar market compared to the most competitive areas in the county. GATS data, not available in all states, was substituted when it was higher than the NREL data, giving what we believe is a more accurate picture of total installed capacity. In the rankings, a distinction is made between cities and counties. County data is used where city-level data is unavailable, or the city and county perimeters are approximately identical. Generally counties yield lower solar densities than cities.

About Sol Systems Sol Systems is a solar energy finance and development firm that was built on the principle that solar energy should be an economically viable energy solution. With thousands of customers and hundreds of partners throughout the United States, Sol Systems is the largest and oldest SREC aggregator. We provide homeowners, businesses, solar installers, and developers with sophisticated financing solutions that help make solar energy more affordable. Sol Systems also helps energy suppliers and utilities manage and meet their solar RPS requirements efficiently by providing them with access to diverse portfolios of SRECs. For more information, please visit In addition, Sol Systems recently launched Sol Market, a transaction-driven ecosystem for the solar industry that catalyzes investment in solar energy by transforming how solar projects are financed.  SolMarket provides investors and developers with the tools they need to efficiently originate, evaluate, finance, and construct renewable energy projects.  SolMarket has over $1.9 billion in committed partnership funds seeking qualified solar projects and hundreds of users from the solar community.  SolMarket is a wholly owned subsidiary of Sol Systems, the country’s oldest and largest SREC aggregator.  For more information, please visit