What is incremental power needed to raise house temp a few degrees with Mitsubishi minisplits?
I have an all-electric house in MA heated exclusively with two MUZ-FH09NAH ( ductless minisplit with pan heater). This is my first heating season so I am still on a learning curve and am desirous to optimize my costs and comfort.
I was pleasantly surprised to find that the Mitsubishis generated heat even as the thermometer plummeted to minus 7.6 F a few weeks ago. We keep them set to 64 degrees indoor but want to know what incremental power consumption would be incurred if we raised temp to 66 or 68 degrees. In order to answer this, I tried to use the manufacturer documentation, linked at the following URL, specifically the table on page 14 and the graphs on page 16, screenshots will be attached.
Reading the heating tables has been frustrating and counterintuitive so I hope for some GBA guidance. I am looking to optimize TPC (total power consumption in kwh).
1. Looking at table on page 14, it looks like TPC is less than 5% higher for raising indoor temp from 65 to 70 degrees (TPC @ 65 of .62 versus TPC @ 70 of .64). That seems a very reasonable increment.
2. It is counterintuitive (for me) to see that TPC *increases* as outdoor intake air temp increases. Shouldn’t the indoor heating TPC be *less* when the outdoor temp is 55 (TPC = .74) degrees than it is when the temp is 35 (TPC = .66)? I realize that the delta temp magnitude drives the heating engine, but my ears tell me that the duty cycle (ie when the outdoor unit is working hard) is more frequent at 35 than 55. Will my Spring heating bills actually be higher than my Winter ones?
3. My confusion is reinforced by what looks to me like an axis error for the graph of FH09NA, which shows the 65 degree interior temp has a *higher* TPC than 75 temp, while the opposite is shown for the FH09NAH graph. I think the typo is on the latter graph, no?
A brief primer on how to understand these tables would be helpful to me.
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