California’s new building energy code ensures that most new homes in the state will produce as much electricity as they consume, using solar power and energy efficient construction to zero out electricity use from lighting, cooling, and plugged-in appliances. While the code drew national attention, the reporting missed a nuance: homes can comply with community solar systems, too.
The recently released "Alternative Approach to Meeting Zero Net Energy Goals Can Benefit Consumers and the Environment", finds that using community solar to power energy-efficient homes can increase both the consumer and environmental benefits of zero net energy programs. Yielding these savings will require overcoming some real-world barriers, however.
More powerful than an individual rooftop
Community solar allows individual households to purchase shares of a larger solar project, sited in their community, instead of getting an individual rooftop system. In the study, commissioned by the Natural Resources Defense Council (NRDC) and the National Rural Electric Cooperative Association (NRECA), analysts from the Brattle Group found that community solar could be a more cost-effective and powerful carbon-cutting tool than individual rooftop installations.
The study compared 200 hypothetical zero net energy (ZNE) homes in both Minnesota and New Mexico and determined that the cost of installing community solar to power ZNE homes was 30 to 35% less than individual rooftop installations, and this is taking into account savings that would occur if rooftop solar were built into a home from the start. With the same total expenditure, the community solar-based approach could produce enough additional electricity production to power another 80 to 90 efficient homes in that hypothetical development.
The savings from community solar are due in part to economies of scale, as well the technological advantages of a large, offsite array. Large solar arrays can be adjusted to catch more light throughout the day as the sun moves across the sky, and be oriented in an optimal direction, and thus generate more electricity than rooftop panels. And by offering an offsite location, community solar enables more people to use solar energy, even if they don’t have enough space on the roof or if their rooftop is shady.
In order for states and cities to take full advantage of community solar in ZNE homes, there are a few real-world obstacles to overcome. Practically speaking, it’s much easier for builders to install individual solar panels than to coordinate with utilities and solar providers to create a community solar project. Policymakers would need to find ways to make community solar an easy option. And homeowners, builders, and code officials would need assurance that the project is in fact being built, and that it will remain connected to the homes in question, just as a rooftop solar panel would be.
The consumer perspective
Finally, from a consumer perspective, the compensation scheme needs to be ironed out. When an individual home’s rooftop panels generate more electricity than the home needs, the homeowner can often get compensated for that excess sold back to the utility at the same rate the individual pays the utility for electricity. It is unlikely community solar will become a popular option for new homes if the homeowner gets a significantly worse deal than they would get if they had instead installed rooftop solar.
Using community solar to power ZNE homes presents a promising opportunity to cut even more carbon, reduce energy bills for consumers, and give low-income consumers access to clean energy. By focusing only on rooftop panels to power ZNE homes, current initiatives may be missing out on this opportunity. As more states and cities seek to cut carbon using mandatory zero net energy building codes, policy-makers need to ensure that community solar is an attractive option for builders, utilities, and homeowners.
This blog originally appeared on the NRDC website.
Written by Dylan Sullivan, Senior Scientist, Western Region, Climate & Clean Energy Program, NRDC