Once you know the PK requirement of your AC, then what you need to do is to find an AC with the same PK that has the highest BTU number with the least Watt consumption. The ratio of BTU (cooling power) to the Watt (energy consumption) is called EER or Energy Efficiency Ratio. The higher the EER the less energy it will consumes.

As a current benchmark, good 1/2PK (5000BTU) AC will require 320Watt, 3/4PK (7000BTU)will require 590Watt, 1PK (9000BTU) will require 795Watt.

Don't be fooled by the cheap AC from China, please check their specs. Most of them will consume higher Watt compare to leading brands. Try to look for branded AC such as LG, Panasonic and Sharp, at the moment they have the lowest wattage.

Another key factor to consider is the max electricity power (Daya PLN) installed in your home. It ranges from 900 to 6600 VA (or Watt). Just make sure that you have enough electricity power to run all you ACs. Otherwise, you don't have other choice than to limit the number of AC installed or choose AC with one step PK lower than it should be (eg 1/2 instead 3/4 PK). Off course the cooling will not be maximum but its better than none.

As an illustration, if you have 2200VA electricity installed, you can only turn on 3 unit of 3/4PK AC at the same time, with only 400-430 watt left to spare for lamps, refrigerator, tv etc. Please note that : microwave, plasma tv, water heater, water pump require a lot of electricity power.

Finally here's some tips to efficiently use your AC : a. please ensure all windows and doors are properly closed, b. please block sunlight by closing your curtain or shades. if you have extra money, you can ask for special curtain materials that will effectively block sunlight like what they used in the hotels, c. trade in your old AC with the new one that has higher EER. Your old unit will be valued at IDR 500-900K depends on their type and conditions. You can find the buyer at the classifieds in the newspaper