What I have learned from A/C Issues I've had in apartments this year:
I have had problems at a building that does not have central air and the tenants tend to use their own AC units. I had two units this year where they were constantly popping breakers with them.
In the first case they had an old window AC with a capacitor start motor that had a tremendous amp draw when that motor started. It was not as inefficient as I would have thought once running, but not that efficient either. The issue is that the power draw on the circuit it was on was enough to blow the circuit. They also had a second smaller AC unit on the same circuit though they claimed they didn't run them at the same time.
In the second case, the tenant had three AC Units. I checked their power draws and found that the PORTABLE AC unit was horrendous for its cooling capacity. I thought the unit might be defective, but it was a new unit and I found the specs online. Turned out it was DESIGNED to be horrendous in terms of power. For an 8K BTU portable air conditioner it was drawing over twelve hundred watts running. It also had a bit of a surge starting. It appears that in its case it uses the warm air generated to try to carry as much humidity out with its exhaust air to make it less of a pain to empty buckets too. Now on a 15 amp circuit with their big screen TV, lights, and other stuff in the room, it was just too much, like a space heater running, and with a surge when the compressor starts up as well. She did tell me on one occasion that she turned on her (1800 Watt) hair dryer and the circuit tripped, but that is a topic for another thread, so I won't get started on hair dryers and why they need their own circuit here.
I did a bit of research and found that the governments rating system in the U.S., the CEER rating is simply the ratio of BTU's capacity to Watts drawn, though the newer CEER as opposed to the EER averages in stand by power consumption as well. That makes things simple if such ratings are available for different models tested. For example, I found a 10K BTU GE profile unit with a CEER of 15.7. I used that for the first situation. It should thus draw about 636 Watts to move that heat to the outside. It is a window unit as was the one it replaced. It is also an inverter unit, so it does not have a huge power spike on startup either. It was however expensive, at $489. But in my case for safety, convenience, and power consumption, though the tenant pays the electric, it is worth it.
Now for that horrendous portable unit. I found that basically all of those units I could find that are sold are horrendous on efficiency, with CEER's in a range from 5 to 7 or so. I simply could not find an efficient one. I had ordered another of the 10K BTU 15.7 CEER GE profile units, but apparently Amazon lost in in shipping and it was refunded. I went to a big box home improvement store in the U.S., Home Depot, and I found that they had an 8K BTU window unit with a CEER of 16. It was the same capacity as that portable one. Now its power draw was just over 500 on the Kill a Watt, and it did not have any significant start up surge as it was also an inverter type unit. I replaced her portable unit with that window unit and told her she would not only be less likely to throw the breaker, but that she would save money on electricity too. That unit draws about a third of the power of her old unit for the same cooling capacity. By putting the compressor outside of the window, it is quieter, and you don't get penalized for turning a space heaters worth of electricity into heat inside your home that you then have to move as well.
After researching this a bit, my conclusions are that portable air conditioners are horrendous on efficiency and should only be used in emergencies. I do have a 10K unit of that type, but I only use it when someones central AC is down for repairs as an emergency backup.
If you are generating your own power with solar or wind the higher efficiency of a unit with a high CEER is worth the cost difference under those circumstances.
If on grid, it is a more complex calculation, you may have to balance the increased costs of a more efficient unit with the actual savings you'd be likely to generate from it. For example, if you replace a 10k BTU unit with a CEER of 10 with one with a CEER of 15, and it runs with a 20% duty cycle for 4 months, the CEER 10 unit drawing 1000 Watts running vs. the CEER 15 unit drawing 667 Watts would save you 333 Watts when running, so if it was only cycling/running 20% of the time, that would be .0667 KWH/Hr over 4 months of cooling roughly, or 192 KWH. If you used it 7 seasons, that would be 1344 KWH of savings. If your only paying a dime per extra KWH in the U.S., that equates to roughly 134 bucks. That is probably about the difference in price of the lower efficiency vs. the higher efficiency unit, and of course you are spending the money up front and getting it back later. You may have other considerations as well, such as in my case, where power limitations of the circuits they were powered by trumped other issue. Additionally there may be features on premium high efficiency units such as online monitoring/control that may have added value for you as well. You should figure your own use case and saving and whether it is worth it for you.
I am happy to report that I have not had to reset breakers yet in either of those apartments since replacing those AC units and a bit of tenant education on hair dryer power draws.
