Water Conservation Saves Energy in California

California is moving away from mandatory water conservation rules. At least for now. Gov. Jerry Brown enacted mandatory 25 percent reductions across the state that went into effect last June, but this spring the State Water Resources Control Board moved to give local water agencies authority to determine how much conservation is needed.

The latest numbers from April show a hopeful sign that perhaps conservation is becoming a way of life in California – even without government mandates. The Water Resources Control Board reported that Californians cut water usage by 26.1 percent in April compared to the same month in 2013. That’s a reduction from 104 gallons (394 liters) per person a day to 77 gallons (292 liters).

Nearly 60 percent of California remains in severe drought, so diligence on water conservation is still pertinent. But the benefits extend beyond just water. Because it takes energy to move and treat water (and wastewater), water conservation also translates to energy savings.

Throughout the last year of mandatory water conservation requirements, the state reported each water supplier’s monthly tallies, so the water savings were clear. But what quantity of energy savings were realized as a result?

Researchers from the Center for Water-Energy Efficiency at the University of California, Davis, decided to find out. The group built an interactive web application which shows that California’s water conservation rate of 23.9 percent over 2013 levels between June 2015 and February 2016 saved 922,543 megawatt hours (MWh) of electricity, or enough to power 135,000 houses for a year. This energy saving also translated into a reduction in greenhouse gas emissions of 219,653 metric tons or the equivalent of removing 50,000 cars from the road for a year.

The research also turned up interesting information about how water and energy conservation efforts stack up. Between July and September 2015 – the only period for which researchers could get overlapping water and energy data – they found that the water conservation measures resulted in a savings of 460 gigawatt hours (GWh). That’s almost identical to the amount of energy saved (459.4 GWh) through all the energy conservation programs put in place by the state’s biggest investor-owned utilities – Pacific Gas and Electric, Southern California Edison, Southern California Gas Company and San Diego Gas and Electric – which provide electricity to 80 percent of residents.

“We thought that was quite significant,” said Frank Loge, a professor of civil and environmental engineering at U.C. Davis and the director of the Center for Water-Energy Efficiency. Not only did water conservation realize about the same energy savings as all the energy conservation programs (like appliance rebates) of the biggest utilities, but the savings via water were way less expensive – $44.8 million for water conservation efforts, compared with $172.6 million for energy conservation programs.

Even the researchers, said Loge, were surprised by the findings.

The key to converting the water conservation savings to energy savings is in figuring out the energy intensity of water supplies, said Loge. Energy intensity is how many kilowatt hours are embedded in a million gallons of water. “In order for water to come out of your tap at home, it requires energy to be pumped into the water system, to treat the water, to pump the water to your house and you might want to consider the energy that goes into disposing of your water as well, so pumping to a wastewater treatment plant and ultimately disposing of it,” he said.

The energy savings from these calculations are realized at the utility, not the home, level. This is cold-water conservation, explained Loge. There is another kind of energy saving through water that can be realized by individuals – hot-water saving. “If I replace my shower head, I’m saving hot water and so I’m now the recipient of that energy saving,” he said. “But for the analysis we did it was not the energy saved through hot-water conservation, it was energy saved through cold-water conservation – the water that comes to your house.”

How much Californians continue saving water, and therefore energy, remains to be seen as water suppliers are back in the driving seat when it comes to conservation rules now.

“What will really be telling is when we’ll be able to see what [water suppliers’] conservation programs are,” said Loge. “They might revert back to the status quo before the drought. I personally think that would not be a good direction. I think there is a lot of opportunity for people to use water more efficiently and I think we ought to be doing that.”

Water Deeply is an independent digital media project dedicated to covering California’s water crisis. The project is part of News Deeply, a new media startup and social enterprise based in New York.