Ross Starfeldt, weary of power outages at his Bloomington house, recently bought a suitcase-size battery to hang on the wall of his garage, becoming one of the first Minnesotans to embrace billionaire Elon Musk's vision of the future.

The lithium-ion battery was built by Musk's Tesla Inc., which is betting on success with battery-operated houses just as with electric cars.

The company this year quietly began selling its Powerwall battery, which can store power generated by solar panels during the day or purchased from the power company at night when rates are lowest. Starfeldt does both.

"When the sun goes down, our house is still using energy generated from our solar panels," Starfeldt said. "It is a good feeling knowing the energy is clean energy."

In the Twin Cities, at least a dozen Powerwalls have been installed, all of them by St. Paul-based All Energy Solar, which has taken orders to install an additional 50 more systems by the end of the year.

"Energy storage has been top of mind for a lot of solar energy customers, but cost has always been a driving factor," said Brian Allen, co-founder of All Energy Solar. "We're now to the point where energy storage makes a lot more sense."

A Tesla representative declined to comment on the Powerwall rollout in Minnesota or elsewhere. Musk first introduced the product at an event in April 2015 and announced a second version last October. Tesla last week said it began production of a related product, roof tiles that collect solar power.

Allen started having conversations with Tesla about ­Powerwall two years ago, he said. The company submitted an application to become a certified installer and the company went through a "full-on vetting," Allen said. Last year, he and a master electrician were allowed to attend an out-of-state training session at Tesla. All Energy began installing Powerwall batteries just two months ago.

Home energy storage isn't new. Deep cell batteries coupled with power inverters have long been used to store energy generated by solar panels, and people concerned with power failures have long had access to gas- or propane-fueled generators.

The Powerwall is compact, easy to use and doesn't require regular maintenance. And while Powerwall users in Minnesota must be connected to the power grid whether or not they own solar panels or a wind turbine, that's expected to change someday. Eventually, people will be able to generate their own electricity, store it for use when needed and be free of the utility system's grid.

"What Tesla is doing is either the wave of the present or the very near future," said John Kearney of the Minnesota Solar Energy Industries Association.

The base price for Starfeldt's system was $6,200, not including installation. The system qualifies for a 30 percent federal tax credit. Even with that, it may take Starfeldt about 10 years to produce a savings from the investment.

A system with installation can cost upward of $10,000, said Ryan Buege, sales and marketing director at All Energy Solar. Consumers who have solar power can sell surplus energy to a utility, helping to speed up their return on investment, he noted.

Leo Babeu of Two Harbors, Minn., has pined for a solar system for at least two decades. His Powerwall and solar system is capable of producing and storing enough power to sustain his family for several days. The system cost more than $9,000 with installation. He also estimates it will take about a decade to justify cost.

"The main reason for the Powerwall was to provide a storage buffer so that we can store and use home-produced energy at night or when the grid is down," Babeu said. "We also expect to be charging an electric car someday and the battery will help us do that overnight."

Laura Hannah, senior policy associate with Fresh Energy, a Twin Cities-based advocacy group for clean energy, said that Powerwall and other energy storage technologies will reduce the stress on an aging electrical grid by shifting more energy storage from a central power grid to individuals at a time when there's more dependence on electricity.

"It will make the grid more flexible and resilient. Homeowners are looking to control where their energy comes from for reasons of greening the footprint or saving money," said Hannah. "It's coming faster than anybody expected."

Jordon Honeck of Maple Grove has a pair of Powerwall batteries that are attached to his garage wall. They cost about $15,000, not including the 30 percent tax credit. While the cost of Powerwalls will likely decline in coming years, Honeck said he bought a system now in case the tax incentives that apply to renewable energy products are reduced or eliminated.

"Our decision to invest in a solar-generation system complemented with Powerwalls was driven by a desire to live on renewable energy," Honeck said. "The addition of the Powerwalls to our solar system installation was done solely to provide the peace of mind of being capable of living off the grid."