AC Installation

The U.S. Department of Energy divides the country into three regions for central air conditioner efficiency standards, because a unit works harder in a hot, humid climate than in a cooler one. Maine falls in the North region. Under the DOE's 2023 test procedure (10 CFR Part 430, Subpart B, Appendix M1), a split-system central air conditioner sold for the North region must meet a minimum of 13.4 SEER2 for capacities under 45,000 Btu/h, or 13.8 SEER2 and 11.2 EER2 for larger capacities — lower than the 14.3 SEER2 minimum required in the South and Southwest regions, since Maine's cooling season is shorter and less demanding on the equipment.

The '2' in SEER2 isn't cosmetic. The 2023 test procedure raised the external static pressure used during testing to better match how a system performs against a real duct system, so a unit's SEER2 number typically reads a bit lower than the SEER number the same equipment would have posted under the old test. A contractor quoting 'SEER2 14' isn't offering a weaker system than one quoted 'SEER 14' under the old label — it's a different, more realistic test, and Maine's North-region minimum already reflects it.

The EPA's Technology Transitions rule, issued under the AIM Act, restricts new residential air conditioning and heat pump equipment built for the U.S. market to refrigerants with substantially lower global warming potential than R-410A, starting January 1, 2025. An interim rule gave some room at the changeover: equipment already manufactured or imported before that date can still be installed through January 1, 2026, so a small amount of R-410A equipment may legitimately still turn up for a while after the deadline.

In practice, new residential systems sold from 2025 onward use replacement refrigerants such as R-454B or R-32 instead of R-410A. For a homeowner, that mostly matters at installation and at end of life: these newer refrigerants are mildly flammable (rated A2L) and require equipment, fittings, and handling procedures built for them, so a system using them needs to be installed and serviced by someone trained on the new refrigerant rather than handed the old R-410A gauges. It does not mean an existing R-410A system already in a house is illegal or has to be replaced — the EPA has confirmed that repairing an existing system, including replacing a major component like a compressor or condensing unit, remains allowed. R-410A is being phased down at the production level, not banned from service work.

A cooling system that's too large for the space cools the air quickly but shuts off before it has run long enough to pull humidity out of it, leaving rooms that read cold on the thermostat but feel damp. ENERGY STAR's guidance is direct on this: oversized equipment cycles too frequently, which hurts both comfort and equipment lifespan, and poor airflow from incorrect sizing or duct design can mean higher bills and reduced comfort even when the equipment itself is efficient. Improper installation generally, not just wrong-sized equipment, can cut a system's real-world efficiency by as much as 30 percent compared to its rated performance. The fix is sizing from the house's actual characteristics — window area and orientation, insulation levels, air leakage, and occupancy — rather than a rule of thumb like square footage alone or simply matching whatever equipment was there before.

All three technologies can cool a Maine home, but they differ in what they need from the house and what they do for the rest of the year.

A central air conditioner only cools, so it makes the most sense where a furnace and duct system are already in place and heating is staying on its current fuel. A ducted heat pump uses the same duct distribution but can heat and cool from a single outdoor unit, which is why it's increasingly the default recommendation in homes that already have ductwork. Where there's no ductwork — an older home, an add-on room, a converted attic — a ductless mini-split delivers the same cold-climate heat pump technology zone by zone, without the cost or disruption of adding ducts.