Heat Pumps & Mini-Splits

The Northeast Energy Efficiency Partnerships (NEEP) publishes the Cold Climate Air Source Heat Pump Specification. Version 4.0 took effect January 1, 2023. Manufacturers who list a product must report its heating capacity at 47°F, 17°F and 5°F, and the unit must meet efficiency minimums, including a coefficient of performance (COP) of at least 1.75 at 5°F when running at maximum capacity.

COP compares heat delivered to electricity used. A COP of 1.75 means the unit puts out 1.75 units of heat for every unit of electricity it draws, even at 5°F.

Efficiency Maine sets its own bar for rebates, and it is stricter than NEEP's in several places. Every unit on its list must also have heating capacity at or below Maine design temperatures.

The low-temperature limit is the coldest air a unit keeps running in. Output at 5°F is how much heat it actually delivers on a cold night compared with its 47°F rating. A unit can run at -15°F and still make far less heat than its label suggests.

Efficiency Maine's list shows both the rated output at 47°F and the maximum output at 5°F for every eligible model, plus the lowest temperature where the manufacturer publishes data. NEEP defines maximum as the output a unit can hold steadily, without time-limited boost modes. Some units list more maximum output at 5°F than their 47°F rating. Others drop well below it.

Wind does not change the math. Efficiency Maine notes that many heat pumps provide efficient heating down to -22°F or lower, regardless of windchill.

Figures come from each manufacturer's spec sheet or product page and Efficiency Maine's list. Each row is one size. Other sizes differ, so compare the exact model you are quoted.

Mitsubishi Electric Hyper-Heat

On Efficiency Maine's list, the Hyper-Heating INVERTER (H2i) MSZ-FS12 pairing is marked ENERGY STAR Cold Climate certified, with performance data published down to -13°F.

Fujitsu XLTH

Fujitsu's Extra Low Temperature Heating series covers the RLS3H and RLXFWH wall units, RLFFH floor units and multi-zone models. A built-in heater warms the base of the outdoor unit once it reaches 36°F so defrost water does not freeze, and the base has drain holes and a metal fan guard.

Daikin Aurora

Daikin uses the Aurora name on ducted and ductless equipment. For ductless, Efficiency Maine lists the FTXV12AVJU / RXT12AVJU wall pairing at 13,500 Btu/h both rated at 47°F and maximum at 5°F, with data published to -13°F.

Bosch Climate 5000

Bosch's Gen 4 Max Performance 12K submittal lists a COP of 1.80 at 5°F, above the 1.75 line NEEP and Efficiency Maine both use.

Rebates are tiered by household income. Amounts below are as listed in September 2026. Programs change, so confirm on efficiencymaine.com before signing.

• Only single-zone heat pumps on Efficiency Maine's list qualify. Multi-zone and dual-fuel heat pump/furnace systems are not rebate-eligible, though multi-zone capacity can count toward sizing.
• New and existing heat pumps must be sized for at least 80% of the home's peak heating load, and heat pumps plus supplemental heat for at least 100%. Your old boiler or furnace cannot count toward that 100%.
• The heat pumps must be the primary heat all season, with the old furnace or boiler kept for emergency backup only.
• The home cannot have had a natural gas utility account before the upgrade.
• The system must be installed by an Efficiency Maine Residential Registered Vendor, and the claim must be emailed or postmarked within 6 months of completion.
• A $500 limited-time bonus applies to eligible whole-home upgrades completed, with claims submitted, from March 1 through December 31, 2026. Single-wide mobile homes have a separate path worth up to $13,900.