I just did a bunch of measurements on my two split units as I was thinking of replacing the SEER 14 unit with a better unit. This is not an apples to apples comparison as the the Fujitsu is an older, and very basic model next to the Mitsubishi.
Watts is measures after my OutBack inverters. I am 100% off grid, so the DC draw is the really critical number and keeps me from messing with power factor math.
Fujitsu AOU9CQ SEER 14 9,700BTU
Watts are DC draw on 48 volt battery bank after Inverters.
75F air input temp.
Mitsubishi MSZ-FH06NA SEER 33 6,000BTU
Watts are DC draw on 48 volt battery bank after Inverters.
75F air input temp.
*Unit seems to very pump output greatly when in heat mode. 1500+ Watts was noticed at times.
The Fujitsu is an older, basic model. The pump cycles between 900 watts and 700 watts, and off. It seems to only have 2 power levels.
The Mitsubishi is new top of the line model. It varies the pump speed on demand.
I am also expecting the Mitsubishi can provide more BTUs as both units air output temp is 50F (with an input of 75F). I suspect Mitsubishi slowed down it's compressor to limit the output air temp to 50F.
If you add it up, the Fujitsu is slightly more efficient at 10.7 BTUs a watt over the Mitsubishi 9.4 BTU a watt. Seems strange that the higher SEER unit is less efficient at full output, but I suspect I am missing something. Possibility the efficiency gains of the SEER 33 rating only really happen at lower speeds.
My goal of the measurements was to see if I should replace the older Fujitsu in my living room with the higher SEER Mitsubishi, but I don't see the power advantage when running at full speed, and I only run it in the day when I am home, and it's on full speed anyway.
I have the Mitsubishi in my bedroom and I run it all night. I love the heck out of this unit for the bedroom. I have measured it running as low as 60 watts just maintaining the room temp all night. That is the same amount of power the fans I was running in the room consumed before I went with an AC.
A note on the Mitsubishi FHXXNA series. The FH06NA (SEER 33) is the 6,000 BTU model. Next to a circuit board change, there is no difference between it and the FH09NA 9,000 BTU (SEER 30) model based on the spare parts catalog. The FH12NA 12,000 BTU (SEER 26) model does have a different pump in the outdoor unit, but that, and the circuit board is it.
I suspect Mitsubishi gets that high SEER 33 number out of the 6,000 BTU unit by basically running the 12,000 BTU unit at half speed, but using the same evaporator and condenser (and maybe a smaller pump). So if the if the BTUs might be needed for a larger room, the 12,000 BTU unit might be the way to go as you will likely get the max BTUs when you need it, but the SEER 33 efficiency if you set to half power.
I guess I should answer the SEER question. Does a higher SEER unit generate more BTUs per watt? At max cool, for an average home application, not that I can tell.
Watts is measures after my OutBack inverters. I am 100% off grid, so the DC draw is the really critical number and keeps me from messing with power factor math.
Fujitsu AOU9CQ SEER 14 9,700BTU
Watts are DC draw on 48 volt battery bank after Inverters.
75F air input temp.
Unit Off | 11 Watts |
Fan High | 23 Watts |
Full Cool | 903 Watts |
Full Heat | N/A |
Mitsubishi MSZ-FH06NA SEER 33 6,000BTU
Watts are DC draw on 48 volt battery bank after Inverters.
75F air input temp.
Unit Off | 14 Watts |
Fan High | 28 Watts |
Full Cool | 636 Watt |
Full Heat | 977 Watts* |
The Fujitsu is an older, basic model. The pump cycles between 900 watts and 700 watts, and off. It seems to only have 2 power levels.
The Mitsubishi is new top of the line model. It varies the pump speed on demand.
I am also expecting the Mitsubishi can provide more BTUs as both units air output temp is 50F (with an input of 75F). I suspect Mitsubishi slowed down it's compressor to limit the output air temp to 50F.
If you add it up, the Fujitsu is slightly more efficient at 10.7 BTUs a watt over the Mitsubishi 9.4 BTU a watt. Seems strange that the higher SEER unit is less efficient at full output, but I suspect I am missing something. Possibility the efficiency gains of the SEER 33 rating only really happen at lower speeds.
My goal of the measurements was to see if I should replace the older Fujitsu in my living room with the higher SEER Mitsubishi, but I don't see the power advantage when running at full speed, and I only run it in the day when I am home, and it's on full speed anyway.
I have the Mitsubishi in my bedroom and I run it all night. I love the heck out of this unit for the bedroom. I have measured it running as low as 60 watts just maintaining the room temp all night. That is the same amount of power the fans I was running in the room consumed before I went with an AC.
A note on the Mitsubishi FHXXNA series. The FH06NA (SEER 33) is the 6,000 BTU model. Next to a circuit board change, there is no difference between it and the FH09NA 9,000 BTU (SEER 30) model based on the spare parts catalog. The FH12NA 12,000 BTU (SEER 26) model does have a different pump in the outdoor unit, but that, and the circuit board is it.
I suspect Mitsubishi gets that high SEER 33 number out of the 6,000 BTU unit by basically running the 12,000 BTU unit at half speed, but using the same evaporator and condenser (and maybe a smaller pump). So if the if the BTUs might be needed for a larger room, the 12,000 BTU unit might be the way to go as you will likely get the max BTUs when you need it, but the SEER 33 efficiency if you set to half power.
I guess I should answer the SEER question. Does a higher SEER unit generate more BTUs per watt? At max cool, for an average home application, not that I can tell.