How much more efficiently does a ductless mini-split perform below peak demand?
My Manual J load calculation for my the 960 sf house I’m building in central Arizona shows a heating load of 13,535 BTU and a cooling load of 11,860 BTU.
I’m debating between two ductless mini-splits:
Panasonic E12NKUA with inverter: 12,000 BTU Cooling 13,800 BTU Heating, 20 SEER 10.6 HSPF
Panasonic E18NKUA with inverter: 17,100 BTU Cooling 20,400 BTU Heating, 18 SEER 8.5 HSPF
The smaller one is less expensive and more efficient at its rated outputs, but the bigger one would easily handle any extraordinarily cold nights. I’ve read here at GBA that a mini-split will run more efficiently than its rated SEER if it’s running at less than its maximum output; I’m not sure whether that would be equally true for HSPF.
At approximately what SEER and HSPF would the bigger mini-split likely perform if it was typically running at 40-60% of its maximum output?
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