Rocky Mountain Power and customers make “one big battery”.

The Rocky Mountain Power program offers discounts to customers who choose to let the utility use their home battery systems when needed.

This story is part of the Salt Lake Tribune’s ongoing commitment to finding solutions to Utah’s biggest challenges through the work of the Innovation Lab.

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The Utah Supreme Court last month ruled against solar rooftop customers who wanted more money for the electricity they sell back to Rocky Mountain Power, but those willing to invest in batteries can still get a break from the utility.

Last month, the court dismissed Vote Solar’s lawsuit against the “net meter” fee rate. Under state law, utility companies are required to purchase excess electricity from solar rooftop customers when they generate more than they use. But the price that energy suppliers pay for this electricity is far below what their customers pay for electricity.

While the solar companies and module owners argue that they should be paid more, the state’s Public Service Commission, which set the tariff, successfully argued that increasing the tariff would force non-solar customers to subsidize solar customers. Rocky Mountain also advocated keeping the lower rate.

Rocky Mountain sings a different tune than those who buy home battery systems. As part of the WattSmart battery program, launched in 2021, the utility is offering thousands of dollars to customers in Utah and Idaho installing home batteries.

But there’s a catch: Rocky Mountain is allowed to use the batteries. Participating customers must give the energy supplier permission to draw power from the batteries if necessary. If more than 3,000 customers are involved, the energy supplier can use the storage battery as a small power plant. Rocky Mountain even lists WattSmart battery customers as a power source in its 20-year integrated resource plan.

“I did it for one simple reason: I like being independent. In today’s world, if the power goes out, you have to have a backup,” said John Walsh, a retired Navy captain who lives in Draper.

To qualify for the credit, customers must select batteries from RMP’s preferred list and purchase enough solar panels to charge the batteries. If they qualify, Rocky Mountain will pay them $400 per kilowatt of battery capacity. For a 6-kilowatt battery system — enough for a medium-sized home — that’s $2,400. New solar and battery installations can easily cost more than $30,000, but there’s also a federal tax credit that covers up to 30% of solar panel costs. Rocky Mountain is also providing an annual credit of $15 per kilowatt to WattSmart battery customers.

In addition, electricity bills are reduced for these customers. “I’ve gone down to $162 a month, down to 9.99 cents,” Walsh said.

Bill Comeau, Rocky Mountain’s vice president of customer experience and innovation, said the battery program is a first step towards a modernized electrical system that can cope with the daily fluctuations of renewable energy sources such as solar and wind. “The grid of the future must be able to store solar energy during the day and use it at peak times.”

Comeau said the utility uses those 3,000 batteries each day for the “daily load cycle,” which addresses the “duck curve,” where peak electricity use occurs in the evening after solar production has faded.

RMP can also use the batteries when renewable energies fluctuate because the sun is behind clouds or the wind decreases.

And it happens automatically. “It’s seamless for customers,” Comeau said.

Walsh said he never realized when the utility might run out of his battery power, but said he had ample power during last winter’s outages. “There were two snowstorms that locked everyone in for two or three days. I had no problem due to my backup batteries.”

Walsh’s system includes an app that tells him in real time whether he’s powering his house with his solar panels and battery or from the grid. This immediate feedback has changed his habits, among other things trying to shift consumption to the time when the sun is shining. “Yes. It motivates me. Do I really want to turn on the light? It makes me think about consumption.”

For Rocky Mountain, the difference between net measurement and battery program is timing. Rooftop solar panels generate additional electricity even as large, utility-size solar farms reach their peak levels. In the western United States, this peak produces so much electricity that utilities can buy electricity for next to nothing and don’t really need the contribution of rooftop solar panels. But that changes when the sun goes down and the price of electricity rises. At this point, utilities can fall back on customer batteries to meet peak demand, meaning they can avoid running coal-fired power plants or buying expensive energy during peak-demand periods.

Those who participate in the battery program can continue to participate in net metering. They will only sell the electricity back to RMP when their batteries are fully charged but their solar panels are still producing.

And Comeau said the program is now open to customers who already have solar panels and want to add batteries.

The program was recently recognized as a “technology pioneer” by the Peak Load Management Alliance for “a unique solution for customers using batteries to convert intermittent solar power into a manageable smart grid asset.”

Similar programs have been developed in Vermont and Arizona, but Comeau said Rocky Mountain is the first utility to make it an option for all residential customers.

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