Green Mountain Power's Home Battery Lease Program Isn't for Everyone-Here Are the Details

The program matches the pricing of GMP’s existing Tesla Powerwall lease program, which charges the same $55 monthly rate, but installation can be costly.

On November 12, 2025, Enphase Energy and Green Mountain Power announced an expanded partnership that adds Enphase battery systems to GMP’s existing home energy storage lease program. The announcement, which was distributed as a corporate press release, presents the program as offering Vermont customers “true energy independence.” However, a detailed examination of the program’s structure reveals significant details that were not included in the announcement—particularly regarding when homeowners can actually use their batteries and what the true costs are.

What the Program Offers

According to GMP’s program page and the official press release, eligible customers can lease two Enphase IQ Battery 10C units through one of two payment options:

• Monthly payments of $55 for 120 months (10 years)

• A one-time upfront payment of $5,500

The two-battery system provides 20 kilowatt-hours of storage capacity and comes with a 15-year warranty, according to Solar Power World. This configuration is generally capable of powering an entire home, including high-demand appliances like HVAC systems and water pumps, according to technical specifications from Wolf River Electric.

The program matches the pricing of GMP’s existing Tesla Powerwall lease program, which charges the same $55 monthly rate, according to GMP’s tariff filing.

The Installation Cost Omission

The announcement’s “$5,500 one-time cost” figure does not represent the total amount customers will pay. According to an analysis by SolarReviews, homeowners must separately pay for installation of the batteries, which brings the total cost over the lease term to between $7,500 and $10,000.

This means customers choosing the upfront payment option should expect to pay between $7,500 and $10,000 in total—the $5,500 lease payment plus an estimated $2,000 to $4,500 for installation. The press release and program materials do not prominently disclose this additional mandatory cost.

The Critical Usage Restriction

The most significant detail omitted from the announcement concerns when and how homeowners can actually use their leased batteries. According to SolarReviews’ explanation of the program: “While homeowners can only use the batteries in the event of a power outage, Green Mountain Power can use as much of the energy stored in the batteries as they want, at any time.”

This restriction is formalized in GMP’s Bring Your Own Device (BYOD) program terms, which specify that customers “may not use the battery system for any controls other than providing backup power for the customer’s premises.”

In practical terms, this means:

• What homeowners CAN do: Use the battery for backup power during grid outages

• What homeowners CANNOT do: Use the battery to reduce their electric bills by shifting energy use to off-peak hours, storing solar energy for evening use, or any other purpose when the grid is functioning normally

GMP maintains operational control of the batteries at all times except during outages, using them as part of its 75-megawatt Virtual Power Plant, according to the press release.

How the Virtual Power Plant Works

The leased batteries become part of what the announcement describes as “the largest dispatchable energy resource in Vermont”—GMP’s 75-megawatt Virtual Power Plant. According to documentation from GMP, this network has saved GMP customers up to $3 million annually in recent years.

The savings mechanism works like this: GMP remotely controls thousands of distributed battery systems across its service territory. During periods of high electricity demand, when wholesale power prices spike, GMP discharges these batteries instead of purchasing expensive power from the regional grid. According to research from Rocky Mountain Institute, this reduces costs for all of GMP’s 265,000+ customers, not just those hosting batteries.

In exchange for ceding control of their batteries, lease participants receive the discounted equipment price. The broader customer base benefits from the $3 million in annual system-wide savings.

The Federal Subsidy Structure

The low pricing of the program is made possible by the 30% Federal Investment Tax Credit (ITC), though this is not mentioned in the announcement. Under the lease model, GMP—as the system owner—claims this federal tax credit rather than the homeowner, according to Utility Dive’s reporting on GMP’s battery programs.

According to that report, GMP’s actual cost for similar battery systems had risen to approximately $22,000, but the utility maintained the $55 monthly customer price specifically because “the federal Inflation Reduction Act provides a 30% investment tax credit for the systems.”

This means the federal government is effectively subsidizing roughly $6,600 of each system’s cost through the tax credit, which GMP captures and uses to offer the reduced lease price to customers.

The timing is significant: according to guidance from Enphase, the 30% ITC for homeowner-purchased systems is scheduled to expire on December 31, 2025. However, lease and power purchase agreement models—like GMP’s program—remain eligible for the credit beyond that date.

The Value Proposition: What Customers Trade

To understand what customers give up in exchange for the discounted price, it’s useful to compare the lease cost to retail purchase prices.

Based on pricing data from renewable energy suppliers, two Enphase IQ Battery 10C units cost approximately $13,000-$13,200 at retail. Additional required equipment (controllers, combiners, etc.) adds roughly $2,000-$3,000. Professional installation and permitting typically costs $8,000-$9,000, based on cost discussions in solar industry forums.

This brings the total retail installed cost to approximately $23,000-$25,000—roughly 2.5 to 3 times the GMP lease program’s upfront price of $7,500-$10,000.

In exchange for this substantial discount, customers provide GMP with:

1. Operational control: The utility can dispatch the battery’s stored energy whenever it determines there is grid need

2. The federal tax credit: Worth approximately $6,600, which GMP claims instead of the homeowner

3. Equipment ownership: GMP owns the equipment; the customer cannot take it if they move (unless they buy out the lease)

Customers who purchase battery systems outright retain full control over when and how to use their stored energy, own the equipment, and can claim federal tax credits themselves (if purchased before the credit’s expiration).

Strategic Context: Enphase and Market Competition

While the announcement frames the partnership as primarily benefiting Vermont customers, it also represents a significant competitive and financial development for Enphase Energy.

Enphase is the dominant supplier of solar microinverters but faces stronger competition in the home battery market. According to analysis from TradingView, the company’s stock price has declined approximately 58% over the past year amid challenging market conditions.

By matching Tesla’s $55 monthly price in GMP’s program, Enphase achieves price parity with a major competitor in what Vermont regulators have called a pioneering utility battery program. The announcement generated positive stock market response, with Benzinga reporting that Enphase shares traded higher following the news.

According to Enphase’s Q2 2025 earnings materials, the company “anticipates a shift in the U.S. solar market towards lease/PPA models.” This GMP partnership validates that strategic direction by demonstrating a scalable utility partnership model.

Program Evolution and Pricing Changes

Evidence suggests this announcement represents an expansion and price reduction from an earlier pilot program. A separate GMP announcement regarding Enphase battery options referenced pricing of $65 per month or $6,500 upfront. The current program’s $55/$5,500 pricing appears to represent both an expansion in scale and a price reduction to match the Tesla Powerwall program terms.

What Happens Next

Vermont homeowners interested in the program can enroll through GMP’s designated program page. According to the enrollment process described by Enphase, approved installers handle the lease agreement, installation, and system setup.

Customers considering the program should:

1. Request total cost estimates that include both the lease payment and installation costs before committing

2. Understand the usage restrictions—batteries can only be used for backup during outages, not for bill reduction during normal grid operation

3. Recognize the trade-off—a substantial discount in exchange for ceding battery control to the utility

4. Consider their backup power needs—whether whole-home backup during increasingly severe storms justifies the cost and control limitations

5. Compare to purchasing—especially if interested in using stored energy for purposes beyond emergency backup

For customers primarily interested in backup power during outages and willing to allow utility control during normal operations, the program offers professionally installed, warrantied battery systems at prices significantly below retail purchase costs.

For customers interested in energy independence, time-of-use bill management, or maximizing their own solar energy use, the program’s restrictions may limit its appeal. These customers might consider purchasing battery systems outright (before the federal tax credit’s December 31, 2025 expiration) or waiting to see how battery programs evolve.

GMP and Enphase have announced that additional products, including a bidirectional EV charger expected in 2026, will be integrated into the partnership in the future, according to the press release.

The program represents Vermont’s continued experimentation with virtual power plant models—using networks of distributed residential batteries to provide grid services while offering homeowners backup power at subsidized prices. Whether this model serves customer interests depends largely on individual circumstances and priorities regarding cost, control, and the value of backup power.