Heating water takes a lot of energy — especially if you are heating it with electricity at peak times, including morning when people are most likely to shower and in the evening when people tend to do the dishes and wash clothes.

That’s why energy misers long ago learned that the best time to heat water with electricity is at night when there’s a surplus of inexpensive electricity. The heated water is then stored for daytime use in big insulated tanks.

Managing consumption has been a vexing problem for utility providers such as Maple Grove-based Great River Energy, a nonprofit cooperative that’s owned by 28 electric distribution members, including the Dakota Electric Association.

But what if that water isn’t staying hot enough? Or if someone is doing five loads of laundry instead of two? Or if your in-laws visit and take long baths and showers?

“At the end of the day we want to make sure they [our members] have plenty of hot water,” said Dave Reinke, energy and member services manager for Dakota Electric Association.

For decades, Great River and other utilities have been installing “electric thermal storage” (ETS) water heaters that store water that has been heated with low-cost, off-peak electricity from 11 p.m. to 7 a.m. using technology developed by North Dakota-based Steffes Corp.

Heating that water overnight is especially efficient in the Midwest where winds are strongest at night and consumption is lowest, creating an abundance of wind-generated power, according to Jeff Haase, Great River’s strategic energy and efficiency program representative.

Haase said there’s a lot at stake because electric water heaters can account for nearly 20 percent of a homeowner’s utility costs and up to 40 percent of the residential demand on the world’s energy grids.

“Our ability to shift these loads into the nighttime hours allows us to use it when it’s being generated,” he said. “This kind of charging program aligns better with our massive amounts of wind energy that are in the market now.”

Those early ETS heaters were able to send out a limited amount of information about usage that was transmitted to the utility via a homeowner’s internet connection. Though the system functioned well, the lack of two-way communication offered limited benefits.

So Great River and Dakota Electric consulted with Steffes, which developed new technology that’s capable of communicating with the utility in real time about the temperature of the water and how much is being used.

The new Steffes Grid Enabled Thermal Storage (GETS) system is a more high-tech version with a new “brain” that allows real-time, two-way communication between the appliance and utility, including the ability to monitor the precise quantity of the heater’s water levels at any given minute, ensuring no one runs out of hot water. And it’s not connected to the homeowner’s internet.

“That was a critical component of this newer project,” Haase said. “It gives us a much larger impact.”

The new grid-interactive electric thermal water heaters were tested with Great River Energy and nine employees of their member co-op, Lake Region Electric Cooperative in Pelican Rapids, before it was deemed ready for prime time.

Reinke said that Great River and Dakota Electric staffers brought the concept to Lakeville-based Country Joe Homes in the late summer of 2016, and the first guest water heater was installed in spring 2017 just in time for the Builders Association of the Twin Cities Spring Preview.

Now, Country Joe Homes has agreed to install those 80-gallon, grid-interactive water heaters in all 81 new homes in the Legacy 2 development, a Lakeville subdivision. Those installations will happen as the remaining houses in the subdivision are built over the next couple years, making it the first community storage development of its kind in Minnesota, according to the utilities.

In addition to the GETS tanks, Dakota Electric and Great River Energy will work with Country Joe Homes to install electric vehicle chargers, advanced air source heat pumps, Wi-Fi thermostats, comprehensive LED lighting technologies and energy-efficient appliances whenever possible in those new houses.

Reinke said that using off-peak electricity will save homeowners hundreds of dollars each year, but it also saves time for the builders because an electric water heater doesn’t require the kind of mechanical ventilation that a gas water heater requires as part of the state’s stringent energy and building code. That means less equipment and at least one less hole in the roof.

“It’s definitely a benefit knowing that we’re providing energy as efficiently as possible,” Reinke said. “And it’s a nice upsell for both the builder and the [power cooperative] member.”