Beyond The Battery: Rethinking Energy Storage

Most of us don’t spend a lot of time thinking about our water heater. As long as we have hot water when we need it, it’s one of those things we only notice when we walk by the tank on our way to change the laundry. But what if your electric hot water heater could double as a battery? Things start to get a little more interesting. That scenario isn’t a hypothetical, according to Dan Phillips, senior analyst of grid innovation and energy efficiency for Wabash Valley Power Alliance. And in the process, you may realize that what can be used as a battery is expanding to more than simply the newest lithium-ion technology. 

Typically, a standard electric water heater — set to, say, 120 degrees — will heat water throughout the day, depending on when it’s used. If you take a shower, hot water comes out of the tank and cold water flows in, which is then heated to maintain the desired temperature. Often, this is a 10-degree range between 115 and 125. Once the temperature of the water in your tank dips below 115 degrees, the thermometer will tell the heating elements to turn on and heat the water. But that 10-degree range can be turned into a form of energy storage without adjusting the water heater’s temperature setting. By heating water when electricity costs less, it decreases demand on the grid during peak hours of the day.

This thinking was summed up nicely in a 2016 report from the National Rural Electric Cooperative Association (NRECA). The report states: “Electric water heaters are essentially pre-installed thermal batteries that are sitting idle in more than 50 million homes across the U.S. By heating the water in the tank to store thermal energy, water heaters can be controlled in real-time to shift electricity consumption from higher-priced…to lower-priced hours.”

In a similar way, most Wi-Fi thermostats can respond to signals from the grid to adjust the thermostat’s setpoints, turning your entire home into a thermal battery of sorts. The better your home’s air sealing and insulation, the longer the “battery” will last by delaying when the HVAC kicks on. Some homes can provide many days worth of storage as proven by the Passivhaus Challenge.

Water heaters, well insulated & air sealed homes and batteries all have one feature in common: They store energy — batteries as a charge and homes and water heaters as heat. While you’re not going to have any luck plugging your cell phone into the water heater when the battery gets low, this ability to store energy gives water heaters and thermostats flexibility. These are examples of ways the Internet of Things is preparing the electric grid for a cleaner future using appliances you probably already have in your home. 

As the electric grid incorporates more renewable sources of electricity, the ability to shift some energy here or store some energy there will become more common. These little shifts when combined across several different, but typical bits of equipment in your home can become significant sources of power. When you start to broaden the way you look at these common household appliances, it will transform the way you use and consume energy.