Vermont's 110 MW Home-Battery Fleet Works Out to 20 kW a Customer

Green Mountain Power says its network of leased home batteries is now Vermont's largest power source at 110 megawatts, and the figure deserves a closer look at what it counts. Spread across the 5,500-plus customers enrolled, it works out to about 20 kilowatts each, a number the sources do not reconcile with a two-battery lease.

The numbers come from a report carried by TBS News, which describes 5,500-plus customers, a $55-a-month lease for two batteries over ten years, and $11 million in customer savings. The utility's own August 2023 announcement gives the baseline: about 2,900 customers, about 4,800 batteries and a network of about 50 MW.

What changed between August 2023 and now

On Aug. 18, 2023, Green Mountain Power announced approval of its request to expand home storage, lifting a 500-customer cap on each of its two programs. The Powerwall program leases two Tesla Powerwall batteries for $55 a month; the Bring Your Own Device program pays up to $10,500 in incentives depending on how much energy the customer agrees to share. A 1,200-customer waitlist for the Powerwall program was full through 2026 at that point.

TBS reports that more than 2,500 customers have joined since the cap came off. The two datasets are not the same kind of document, one a utility release and the other a news report, so the comparison below is a rough one.

Measure	August 2023 (GMP)	TBS News report
Customers with home batteries	about 2,900	more than 5,500
Network size	about 50 MW	110 MW
Reported customer savings	up to $3 million a year	$11 million

1. August 202350 MW
2. TBS report110 MW

Source: GMP release of Aug. 18, 2023 (about 50 MW); TBS News report (110 MW), accessed 2026-10-01

The 110 MW denominator

The number that matters here is not 110 but what each megawatt is made of. Divide 110 MW by 5,500 customers and each household accounts for 20 kW. The 2023 figures give a similar ratio: 50 MW over 2,900 customers is about 17 kW. A lease covers two batteries, so the arithmetic implies about 10 kW per battery if every customer leases a pair.

Neither source states per-battery output, and the Bring Your Own Device customers use their own equipment. So the 110 MW could be a sum of nameplate ratings, a dispatchable figure under the utility's control, or a mix. For a grid operator these are different products: nameplate is what a battery could do for an hour, and dispatchable is what the software can call on at 6 p.m. when every battery is also being asked to ride through an outage. None of the sources fetched here say which one Green Mountain Power means.

Who pays, and how much: $55 a month over ten years

A $55 monthly lease over a ten-year contract is $6,600 per household. If all 5,500 customers paid that rate, lease revenue would be about $3.6 million a year, an upper bound because BYOD customers do not pay a lease. TBS reports $11 million in customer savings, roughly three times that. The savings figure is not defined in the report: it could be avoided peak-power purchases spread across all customers, which would make it a system benefit rather than a household one.

That distinction decides who the programme is for. A customer who signs a ten-year lease gets backup power; the wider customer base gets lower peak costs. TBS cites one customer who avoided buying a $12,000 gas generator, a household-scale comparison that fits the first case.

Mari McClure, Green Mountain Power's president and chief executive, framed the 2023 approval in resilience terms: "Accelerating storm resiliency is our path forward, especially after what Vermonters have gone through this year." TBS adds that seven of the utility's ten most damaging storms came in the past decade, with more than $225 million in damage.

Replacing power plants: what is true and what is not yet

The headline claim is that batteries are replacing fossil plants. TBS says four peaking plants remain for occasional use and that McClure described the older plants as "gradually decommissioned" at end of life. That is retirement on schedule rather than a battery fleet displacing running generation, and the report does not say how many megawatts of plant have gone.

The plan TBS describes runs to 2034: double the network, offer storage to all roughly 300,000 interested customers, and explore vehicle-to-grid. A goal to end outages by 2030 sits alongside it. TBS also carries the structural criticism that utilities have limited financial incentive to manage demand, because traditional infrastructure investment is more profitable. For another look at how hardware is priced for the home, see our piece on the $3,555 Flourish One; for the same denominator question applied to machines, see Digit 5's unit economics.

What would change my read

A published split of the 110 MW into nameplate and dispatchable, with the number of events dispatched and the state-of-charge floor, would settle the question. If dispatchable output is well under 20 kW per customer, the "largest power source" framing describes capacity on paper. If it is near that, the programme is doing what the headline says. Green Mountain Power has not published that split in the sources reviewed here.