Eighty-six utilities in 33 states have approved customer use of meter socket adapters (MSAs) for connecting residential distributed energy resources, based on data provided on the websites of MSA manufacturers Tesla, ConnectDER and Enphase.
That’s according to a joint regulatory filing by Efficiency Maine Trust, the Maine Office of the Public Advocate and the consultancy EquinoxDG (available as filing #43 in this docket).
An MSA attaches to a home’s electric meter socket, and is electrically connected to solar panels, energy storage or an electric vehicle charger—or potentially all three. This wiring approach bypasses the main electrical panel and can eliminate the need for a costly panel upgrade.
But even in the 33 states, not all utilities allow the use of MSAs. Maine is one example. The joint parties’ filing recounts numerous roadblocks that Maine utility CMP presents to the wide use of MSAs, quoting a CMP comment that MSAs can create “serious safety hazards.”
But Vaughan Woodruff, principal of EquinoxDG, said on social media that certification to the UL 414 standard addresses safety concerns.
Equinox DG and the two other joint parties called on Maine regulators to require the state’s transmission and distribution utilities to permit a customer to use an approved MSA provided that certain conditions are met, including that the MSA model is certified or listed in accordance with UL 414 or an equivalent standard, and that the installation also meets certain criteria.
For advocates in other states seeking to address utility concerns on MSAs, Woodruff said the joint comments “get into the weeds on the standards governing MSAs while highlighting the importance of safely giving customers access to these devices.” He highlighted how wider approval of MSAs can reduce electricity costs for all customers by facilitating participation in virtual power plants consisting of distributed home batteries.
Home batteries
The joint parties see wider use of MSAs as key to wider adoption of home batteries, particularly through Efficiency Maine’s small battery incentive program, which offers incentives to battery manufacturers to compensate battery owners for delivering energy to the grid at times of peak demand.
The parties quote Josh Oxley, owner of solar installation firm Logix Maine, saying that using Tesla’s Backup Switch MSA for a residential installation of a Tesla Powerwall 3 saves $700 in parts and two hours or more of an electrician’s labor compared to another approved method.
“This scale of cost reduction has a material impact on the overall success and impact” of Efficiency Maine’s small battery program, the parties say.
“Batteries offer more than just backup power,” Efficiency Maine says on its website. For a customer who uses 600 kWh of electricity per month and installs a 15 kWh battery, Efficiency Maine projects battery sharing payments of $500 per year plus $500 per year in time-of-use savings, for a customer who switches to the utility’s time-of-use rate, stores low-cost off-peak power, and uses it when grid power is most expensive.
Over ten years, the net cost of the $20,000 battery would be $10,000, thanks to ten years of payments and savings totaling $1,000 per year.
For a household that uses more electricity, such as an EV owner with a heat pump, a 30 kWh battery costing $30,000 would also have a net cost of $10,000 over ten years, thanks to a doubling of the annual payments and savings, Efficiency Maine says.
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