hill country observerThe independent newspaper of eastern New York, southwestern Vermont and the Berkshires


News & Issues July 2015


In Rutland, solar power’s next step

High-tech storage battery set for debut this fall


Contributing writer



Photovoltaic panels collect the sun’s energy at the Borkowski family’s home in Rutland, which Green Mountain Power has dubbed the “energy home of the future.” This fall, the utility will begin offering a new high-tech battery that will allow homeowners to store some solar power on site, rather than feeding it onto the power grid. Joan K. Lentini photo

The local utility company’s effort to transform Rutland into the solar-power capital of the Northeast will take a technological leap forward this fall with the introduction of a new home battery for storing solar energy.

Green Mountain Power is partnering with Tesla Motors Inc., a Silicon Valley company known for its premium electric vehicles, to introduce Tesla’s new solar home storage battery, beginning in Rutland. GMP is the first utility company in the nation to work with Tesla on the project.

The first of Tesla’s new lithium-ion batteries, known by the brand name Powerwall, is expected to become available in October or November. The battery will improve the efficiency of home-based solar systems by making it easier for homeowners to store some power on site rather than sending it onto the utility grid.

The Powerwall comes in two models: a 7-kilowatt-hour version for daily recharging from photovoltaic panels; and a 10-kilowatt-hour model that can provide back-up power during outages. The latter model can be installed at homes without solar panels and be charged from the utility’s grid.

The slim rectangular batteries can be mounted on an interior wall, are good for 10 years, and can be recycled at the end of their lives. They’re expected to cost around $3,000 for the 7-kwh version and $3,500 for the 10-kwh model. Installation and an inverter (to convert the battery’s direct current to household alternating current) will add to the price.

“We see a huge benefit from these new batteries,” said Josh Castonguay, who, as Green Mountain Power’s director of generation and renewable innovation, worked with Tesla to bring the batteries to Vermont. “It’s an elegant package solution.”


Matching power to demand
The batteries represent a new answer to one of the great challenges for solar and wind power, which is that their production is intermittent: The sun sets, and the wind doesn’t always blow.
Sunlight peaks at noon, but homeowners usually have the greatest need for power in early morning, when they get up and prepare for their day, and in the evening, when they come home from work and turn on the lights, heat or air conditioner, TV, computers and appliances.
The first solution to this problem was lead-acid battery systems. Lead-acid batteries are widely available, moderately priced, clean, safe and easily recycled. But they are heavy, bulky and require maintenance.

A more widely used solution in recent years has been net metering, which allows customers who produce solar or wind power to sell the excess to their local electric company. Customers pay for the energy they consume, less a credit for power they sold to the utility.

Under net metering, there is no need for batteries or their associated storage space or maintenance. The drawback is that in some areas, so many photovoltaic systems are putting power onto the grid that the utilities can’t take any more, and the excess power is wasted.
Now the demand for electric vehicles has spurred the development of lighter, more durable batteries, and Tesla’s Powerwall applies this technology to residential needs. The Powerwall will improve homeowners’ ability to store power and give them more flexibility in how they use it.
Tesla, which didn’t respond to a request to comment for this story, is also working on energy storage systems for businesses and utilities. Powerwall prototypes were tested with major companies including Amazon, Wal-Mart and Target.

Tesla isn’t the only company in the energy storage market. For example, JuiceBox Energy Inc., a Silicon Valley startup, introduced its own home battery system in April. It can be controlled remotely from cellular devices with Web access.


Personal connections
Although Green Mountain Power is Vermont’s largest electric utility, it is relatively small by national standards, so its role in introducing Tesla’s Powerwall is something of a coup.
Castonguay said the connection began several years ago when a summer intern at Green Mountain Power went on to work for Tesla.

“We stayed in touch,” Castonguay said. “We’re doing a lot of transformation ourselves, and we’re looking for strategic partners. We’re always checking with other folks who do storage systems.”
The alliance with Tesla fits in well with the utility’s efforts in recent years to make Rutland a model city for the use of solar power. When it merged with Central Vermont Public Service in 2012 – a merger that resulted in the elimination of the former CVPS headquarters in Rutland – GMP set a goal of creating the infrastructure to produce 6.25 megawatts of solar power in the city by 2017 – enough to supply more than 1,000 of Rutland’s nearly 8,000 homes.

Although the Powerwall will make its debut in Rutland, which GMP calls its “energy innovation center,” Castonguay said the utility will “pretty quickly” make the batteries available throughout Vermont.

There’s definitely interest. Tesla reported receiving 38,000 Powerwall reservations nationally as of May 5. In Vermont, “we had inquiries as soon as the announcement was made,” Castonguay said.

The market, he explained, is people who already have or are considering home solar power -- and those who don’t have solar but want a backup power source.

“Most customers will want a single battery with an inverter,” Castonguay predicted.
But he said the utility still needs to do more work to assess the demand for the batteries. One potential market is for non-solar homes in remote areas that are prone to power outages.

“We’re looking at reliability,” Castonguay said. “Where is it most difficult to keep the power on?”
Most outages last from two to four hours. The 10-kwh Powerwall can comfortably handle a home’s critical load – a refrigerator, lights, a well pump and maybe an energy-efficient TV -- for that length of time, he said. And the battery won’t create noise or fumes like a diesel- or gasoline-powered generator.

Green Mountain Power is still calculating pricing and incentives for the batteries, Castonguay said. The utility has to buy power at premium prices from the New England grid when it can’t meet peak demand. So if stored power from home batteries helps reduce demand peaks, resulting in lower costs for the utility and its customers, the company has an interest in promoting them, he said.

The batteries will be installed by private contractors, Castonguay said.


‘Wave of the future’
The alliance between Green Mountain Power and Tesla is drawing praise from renewable-energy advocates around Vermont, which has set a statewide goal of obtaining 90 percent of its energy from renewable sources by 2050.

Karen Glitman, the director of policy and public affairs at the Vermont Energy Investment Corp., said the Powerwall project “is quite a testament to the progressive nature of Green Mountain Power.”

“There are already a fair number of renewables in the state,” she said. “This is the piece that connects it all.”

Glitman said the software that comes with the Powerwall will allow utility customers to be “energy smarter.” Customers who pay time-of-use rates will be able to draw on the battery rather than the grid at times when electricity is most expensive. And those who pay flat rates will help lower peak demand when they power their homes from the battery during those critical evening hours.

Energy is lost when electricity has to be transmitted long distances, Glitman said. That loss can be avoided if someone is able to charge an electric car, for example, or run a cold-climate heat pump from power that was generated on-site and stored earlier in the day.

The state still needs “aggressive efficiency” to reduce its total power demand, Glitman said. But improved storage “boosts the value of solar” and can also make electric vehicles, which are three times more efficient than gas or diesel-powered models, more attractive, she said.

Dylan Zwicky, a clean energy associate at the Vermont Public Interest Research Group, said the Powerwall project is “a good step.”

“It complements net metering,” he said.

Zwicky suggested the availability of the batteries might prompt some customers to increase the size of their solar installations so that they’re able, for example, to store power for electric vehicles.

Rutland Mayor Chris Louras said the Powerwall project represents “the wave of the future” and gave credit to Green Mountain Power’s chief executive, Mary Powell, for pursuing it.

“We’re still dealing with 19th century distribution technology, what Mary Powell calls ‘twigs and twine,’” Louras said. “We want to generate electricity as close as possible to the end users.”
He said the changing technology might help the region to adapt to climate change.

“We’ve had storms of greater intensity in the last eight to 10 years, coming more often,” Louras said. “We need to use renewables as our primary source and technology to store energy on site so we don’t have to rely on outside sources during disasters.”

Louras also sees economic benefits for the city in the Powerwall project and GMP’s other solar power efforts.

“As we become a hub for energy innovation, we become a hub for sustainability in food and energy,” he said. “Those are two areas we’ve identified that can marry well with our traditional industrial and manufacturing sectors that are job drivers now. We’re confident that out of the sustainability sector, we’ll see job growth.”


Economical, or a novelty?
Steven Letendre, a professor of policy and public affairs at Green Mountain College and director of the college’s renewable energy and eco-design program, dubbed the GMP-Tesla partnership “Utility 2.0.”

“This is a continuation of GMP’s interest in new technology, what they mean to customers, and how they can improve the customer’s experience,” he said. “GMP sees a trend to more distributed energy, and storage is part of that. Tesla has been on the early edge of technology.”
Some industry analysts have questioned whether homeowners will save enough on their electricity bills to offset the considerable up-front cost of a Powerwall.

“It depends on the different ways to use energy storage, how the utility company serves you, and its rate structure,” Letendre said. “In places with time-of-use rates, the price of power at night is usually much lower.”

So customers could draw on battery power to avoid the most expensive rates and stock up on cheap grid power at night. But very few American households have time-of-use plans, and the Powerwall might not be cost-effective even for all of them, Letendre said.

For customers who would want a Powerwall as an emergency power source, “it’s hard to put a dollar value on that,” Letendre said. “But you could buy a generator at Home Depot.”

Still, the Powerwall “is an exciting innovation,” Letendre said. “People who buy them won’t be driven by economics but by self-reliance and novelty. A lot of home solar systems can’t be used in outages, because the inverters stop when the power goes out. It’s a safety feature to protect crews working on the lines. Grid storage will be very attractive. People can store their own power and use it during outages.

“It won’t be cost-effective in the short term,” he predicted. “But if the price of power really reflects its cost, it may be better in the long term.”