- Green Mountain Power (GMP) said its residential battery storage program, rolled out last year in Vermont, saved $500,000 by reducing peak demand during the July heat wave.
- When temperatures spiked on July 5, GMP called on about 500 of Tesla Powerwall batteries to send power to the grid.
- GMP partnered with Tesla last year to offer the Powerwall 2 batteries to 2,000 customers, which could potentially help reduce peak load by 10 MW. The utility will continue to roll out the remaining 1,500 batteries in its program.
Utilities are beginning to see the impacts of recently installed grid edge technology, and a major goal of storage programs is peak demand reduction. The virtual power plant GMP is developing with Tesla is expected to save up to $3 million across the program's lifetime.
As the price of battery storage declines, residential interest has grown — particularly when combined with distributed solar. GTM Research predicts a four-fold increase in the market, with residential installations rising from 19 MW in 2017 to 74 MW this year.
GMP's customers can buy the Powerwall 2 for $1,500 or pay $15 per month, less than half the cost of a pilot the utility ran two years ago. The offering illustrates how rapidly the cost of storage is declining — a similar pilot run with Tesla's first Powerwall in 2015 cost customers $37.50/month.
According to the utility, the batteries can supply all of a home's needs for up to 12 hours and can continuously supply 5 kW, or provide up to 7 kW at peak demand.
Tesla has continued to improve its residential battery offerings. Earlier this year, the company rolled out a software update that allowed Powerwall 2 owners to optimize charging and discharging around time-varying rates. The company said it plans to triple battery deployments this year. In the fourth quarter of last year, it deployed 143 MWh of energy storage products, growing 45% over Q4 2016.