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We have two main models here, one with a sizable compressor enough to heat a whole home (7-20 kW heat) and a water tank on the side which doesn’t need resistive backup, or smaller, hybrid models that have a few hundred W compressor and maybe 1-3 kW heat output. The latter are almost all backed up by a gas boiler in a hybrid setup, usually uses zero gas until you run it dry - then the 25ish kW gas powered furnace can provide enough power to quickly fill a bath or send tons of hot water to a rain shower.
The 200% seasonal efficiency is a bit off, Nordic models, measured with the “colder” European climate zone, get 300%+ and have guaranteed output at -25C / -13F. Example model from Mitsubishi:
It’s worse than 5.5x or 4.3x in warmer areas but the right model air source heat pumps work fine down to pretty damned cold. Norway and Sweden have a ton of them as they spend a ton of energy on heating and this saves homeowners a ton of money every year.
Best models optimized for average climate now reach 5.5x or better in the green, moderate zone, SCOP of 4.3 is actually pretty terrible but this one is built to be ice proof.
Example latest bestest heat pump with 6+ seasonal COP: