Is a heat-pump water heater in Zone 7 worth it?
I’m currently designing a highly efficient 2 bedroom 1080 sqft house. Right now I am wondering if a heat pump water heater would pay itself off before it needs to be replaced. Also, the mechanical room would only be 3’6″ x 7’6″, not big enough size for manufactures recommendations of 10’x10’x10′
My question is how could I run the numbers to see if buying one is a good investment?
Why aren’t there any systems that have an outdoor unit and an indoor unit like HVAC air-source heat pumps? HVAC systems maintain a COP of 2.0 even during -5*F weather? Would the COP of a water heating system be less than 1.0 during winter months due to the delta-T in-comparison to an HVAC system? Say from -15*F to 70*F = 85*F delta-T for the HVAC system and -15*F to 120*F = 135*F delta-T for the water heating system?
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