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?
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.