(Photo: A DOE design competition to develop cost-effective, zero-energy ready homes for mainstream builders. Credit: John De La Rosa/NREL)Rocky Mountain Institute published a report showing that the cost increase to build a zero-energy or zero-energy ready home is much less than many realize. In the United States, developers can even construct these homes at cost parity in certain locations, according to RMI.
The report, called Economics of Zero-Energy Homes: Single Family Insights, shows that costs for new ZE and ZER building are expected to continue declining as the market matures. In addition, the report authors Jacob Corvidae, Michael Gartman, and Alisa Petersen make recommendations for ways builders can minimize incremental costs during construction.
Zero-energy homes that produce or procure as much renewable energy as they consume over the course of a year are often marketed as luxury homes, but the economics have changed, the authors say.
“ZE homes have quietly passed cost thresholds that make them not only good for the environment but also cost-effective,” Petersen and Gartman wrote. “As the underlying technologies and design elements continue to improve and scale, these costs will continue to decline.”
One of the main insights from the report is that ZER and ZE homes can already approach cost parity.
“Contrary to popular belief, ZER homes fall under a 3% incremental cost in most parts of the country, with that cost dropping under 1% in select locations such as Houston, Texas,” the report authors say. “Developers may even be able to construct these homes at cost parity in locations with stricter baseline codes and aggressive incentive offerings from local utilities.”
Solar panels needed to bring zero-energy ready homes to zero-energy bring the incremental cost to 7%–8%, but a wide range of solar financing options can cover part of all of that, the authors added.
Another takeaway is that not all ZE homes are created equal with respect to cost. “In the climate zones we analyzed, ZE and ZER levels of efficiency could be achieved without aggressive or cutting-edge envelope and HVAC solutions,” the authors note. “Although these solutions may yield other benefits such as thermal comfort or passive resilience, from a strict cost standpoint, removing these leading-edge solutions from the ZE package resulted in a significantly lower cost premium.”
Across all climates, the research showed that the cost optimal solution included 100% LED lighting, low-flow water fixtures, and Energy Star appliances as well as heat pumps used for space and water heating. The report called heat pumps an essential opportunity for ZE and ZER home builders.
“The roof, walls, and windows were efficient but did not exceed the DOE Zero Energy Ready Home prescriptive efficiency levels,” the authors added. “Although there is no one-size-fits-all cost-optimal solution to building ZE homes, our analysis indicated that these energy measures are cost-effective in almost any situation.”
Cost is expected to continue declining, with industry progress and demand for super-efficient building components driving cost savings over the next decade, according to the authors.
The new report comes on the heels of an RMI and Urban Land Institute guide for portfolio owners and managers showing how to achieve cost-effective deep energy retrofits that lead to net-zero for an entire portfolio.
