On non-Inverter ACs, I only need to use the power input (e.g. 800W) to calculate my energy cost for a 12-hour usage. (800*12/1000 = 9.6kW-hr)
On Inverter ACs though, I know they don’t operate at 100% all the time, and most of the time the only information I get is their cooling capacity (e.g. 1hp ≈ 746W) and their EER (e.g. 12.2 kJ/hW).
How do I use these to get a rough estimate of the energy cost?
Conventional ACs don’t “operate at 100% all the time” either. The compressor is cycled by the thermostat. You cannot calculate consumption of either without knowing the temperature gradient between the conditioned and outside space.
It gets even more difficult with inverters… they’re unquestionably more efficient as they don’t run balls to the wall all the time, but without taking actual readings and logging them the math is basically impossible.
I’d say it’s pretty damn difficult for both. The VFD speed is dependent on the gradient, just like the duty cycle of a conventional AC is.
Great point. The temperature delta changes all the time. It’s almost impossible to accurately know even with rough math. Might be what you came up with using historical data, might not, if the temps are unseasonably warm or cold.