Solar and battery interconnection rules in Connecticut

Size bands and what each one obliges

The screens that decide it

• Aggregate generation within the service transformer nameplate rating 100 percent of service transformer rating, a figure only the utility holds.

  The first fast track screen is that aggregated nameplate generation capacity does not exceed the nameplate rating of the service transformer.

• Aggregate generation under 15 percent of line section annual peak load 15 percent of line section peak load, a figure only the utility holds.

  Connecticut applies the classic 15 percent screen measured at the substation, and permits the utility to substitute its hosting capacity map data at its discretion.

Ask the utility this, before you sell it

1. Does this project include a battery? Connecticut counts additional AC capacity attributed to a storage system toward the interconnection application level even though it does not count toward the 25 kW AC incentive cap, so a 20 kW solar plus 10 kW battery job leaves the cheap residential lane and pays $500 instead of $200.
2. A certified three phase system of about 22 kW falls between the residential guideline, which covers single phase at 20 kW AC, and the fast track guideline, which excludes inverter projects of 25 kW and less. Which process applies?
3. What is this customer highest annual consumption over the past five years? The incentive program limits expected annual production to that figure plus five percent, plus an allowance for planned electric vehicles and a whole home heat pump.

Worth knowing before you quote

Connecticut requires no insurance at all for a residential system of 20 kW AC or less, which is stated plainly in the guidelines. Legacy net metering closed to applications submitted on or after 1 January 2022 and new customers take the Residential Renewable Energy Solutions tariff, which is rate set to a deployment target of 50 to 60 megawatts a year rather than a hard capacity cap. Connecticut uses 87.5 percent as the short circuit interrupting capability limit where Massachusetts uses 85 percent. The summary insurance table in the published fast track guideline is misaligned by one row in the source document; the prose governs.