Can All New Cali Homes Go Net-Zero By 2020?

By 2020, every one of the thousands of homes built in California each year should be generating its own energy, according to state Assemblywoman Lori Saldana. New homes built after that date would be required to draw zero net energy from the power grid — feeding back into the grid at least as much energy as they consume — under a bill introduced earlier this year by Saldana and considered by the state Assembly Natural Resources Committee yesterday. Can all new homes in California really generate their own power?

In theory, if money is no object, then you could get some kind of clean energy system for most residential structures. Solar panels on the roof, maybe small-scale wind installed in the yard and a geothermal heat pump system underground. Cutting residential energy demand — or at least limiting its growth — could be significant for grid operators in California, where the residential sector accounts for more than 30 percent of electricity consumption.

But money, of course, is an object. California’s residential construction has already slammed into a wall along with the economy, and yet many would-be home buyers still find themselves priced out of ownership. Will state lawmakers really want to slap on an extra construction expense? As the Associated Press reports, Saldana proposed a similar mandate last session. While it passed the Assembly, it didn’t survive the state Senate.

The Department of Energy has a standing goal to “create technologies and design approaches that lead to marketable zero energy homes by 2020.” To help grease the political wheels for a more aggressive mandate in California, Saladana has included two caveats in her proposal. Yeah, zero net energy homes by 2020 would be great, but if photovoltaics aren’t “cost effective” by then — as determined by the State Energy Resources Conservation and Development Commission — then the mandate would be pushed back. And generation doesn’t have to be literally on-site with new homes, just nearby.

The idea of zero net energy buildings is also not new, but it has a few different interpretations. In DOE shorthand, zero energy buildings produce as much energy as they use — never mind the energy used for materials and construction. In setting a timeline and standard definition for the mandate, California could set the bar for other states looking at distributed generation and zero net energy rules. Here’s the definition used in the current draft:

the term “zero net energy building” means a building that implements a combination of building energy efficiency design features and clean onsite or near-site distributed generation that result in no net purchases from the electricity grid on an annual basis and produces enough electricity to offset the energy use attributable to an onsite use of purchased natural gas.

Translation: Homes wouldn’t have to be off-the-grid — totally disconnected from the electric utility — to be in compliance. So when local clean resources aren’t available (cloudy and non-windy days, for example), residents could tap the grid. Then when a home system is pumping out more power than needed at the time, it would feed into the grid. Over the course of a year, the feed-in would have to be about equal to the draw.

Implementing and enforcing such a rule presents no easy task. As BLDG 2.0, one of the LaunchPad finalists at our Green:Net conference last month pointed out, anticipated energy needs and actual use for even the greennest of building designs can be very different.

One place where this proposal falls short is in its focus on new construction. California has more than 12 million existing housing units, and the government expects some 220,000 new units to be needed every year between now and 2020 to accommodate the growing population. If it will be on hold until clean energy, or at least PV technology, is deemed cost effective anyway, then why not address retrofits?

Photo courtesy Flickr user rankun76