The science · Section II

It doesn't make heat. It moves it.

That single distinction is why a heat pump can return up to 30 BTU of heat for every watt it draws — even below freezing.

01 The cycle

Heat from cold air

Fig. 3 — Refrigerant gathers heat from cold outdoor air, a compressor concentrates it, and the indoor head releases it.

02 Step by step

Outdoor air gives up heat

Even at 5°F, air holds usable heat. Colder refrigerant in the outdoor unit pulls it in.

The compressor concentrates it

Compressing the refrigerant raises its temperature sharply — a little warmth becomes plenty.

The indoor head releases it

A fan blows across the hot refrigerant coil, and warm air fills the room.

Summer: the cycle reverses

Run it backward and the same system pulls heat out of the home — air conditioning included.

03 Reading the labels

HSPF2

Seasonal heating score

Heating Seasonal Performance Factor (v2), the current stricter efficiency standard. Higher is better; cold-climate units hold up in Maine.

BTU/W

Heat per watt

Heat delivered per unit of electricity. Top cold-climate units reach up to 30 BTU/watt.

COP

The plain ratio

Coefficient of performance. COP 3 = three units of heat per unit of electricity — "300% efficient."

Efficiency Maine rebates require a cold-climate unit on its qualified product list, sized for at least 80% of the home's peak heating load. The Seville and Keen units offered by the recommended installers are chosen to clear that bar.

No cost · No obligation

The facts point one way. Get your numbers.

A registered Maine installer will size the system, confirm your rebate tier, and quote the net cost — at no charge.

Quote from BRF Services Maine Energy Services