Quote:
Originally Posted by jeff5may
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I'm not sure I can agree with the full load efficiency listed for variable speed compressors.
..sure, a 30+ SEER 9k or 12k unit might be at 18 EER(or a little lower depending on this unit) under high load, but this really isn't bad at all because you are still kicking the crud out of 13 SEER 11 EER units.
In some cases the lower efficiency sub-20 SEER variable speed units, especially larger units do seem to be as bad at high load at cheaper 13 SEER units but that's only at peak loads which isn't an all the time scenario and isn't worse than a common old fashioned single stage split unit.
Moral of the story but a high EER rated inverter mini-split if you are planning to run at high load and that's not an issue and you get the best efficiency in any condition. It seems that the outdoor condensor coils on the smallest units often have the same coil on them between the 9k and 12k sizes and sometimes even have the same coil as up to an 18k size, in which case getting the 18k size might be a compromise but the efficiency becomes clear looking at the EER number. ..of course aiming for a high SEER will give you the best information for cooler conditions and lower load but I wouldn't oversize a unit based on the chart above if buying a good top efficiency unit.
I'm still not sure how you'd arrange getting the compressor to ramp load with the excess solar generation though, that's the trickiest part.