The smaller, residential units have 1/3 to 1 ton compressors in them, plus resistance heating elements for "turbo boost" demand water heating during high usage. Most of the units have an average COP (aka energy factor) of 2 - 2.5. The commercial units (above about 80 gallons) go up from there in both compressor size and COP. Nearly all of the units produced before 2015 had cap tube metering systems in them. Many of the modern units still do, but some are now being built with electronic expansion valve systems, which should theoretically boast higher COP as long as they don't fall back on resistance heating very often.
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