Home a/c systems – Why is it more efficient for it to run continuously a couple of hours rather than cycling on/off so often?

Question

For the sake of argument and discussion, let’s use a perfectly matched, balanced, and calibrated R-410a home a/c system as an example.

Why do folks say it’s more efficient for said home a/c system to run continuously for 2 hours and then off for 5 minutes instead of cycling on/off much more often to achieve the same interior cooling setting on the thermostat? (I understand how home a/c system work, but I’d like to know why some say longer run times = greater efficiency.)

I’ve heard this claim time and again, but I’d like to know the science behind it. I live in Texas where a/c units run for hours during the day from June through September.

In: Engineering

Answer 1

You want it constantly dehumidifying, which means leaving it running so it can cycle all the house air through it. When it’s really humid in the house you can lose roughly half of your cooling capacity to condensing moisture out of the air, not cooling the air. So when you run constantly and keep the humidity down, you’re using your AC to cool your house air, not just dehumidify it. So you don’t have to use as much energy to cool it down and dehumidify at the same time.