i have a question that only requires an approximate answer.

i have to price a large residential block in London, the man making the decision is a real pain, and wants to estimate the running costs. the system will be inverter driven a/c, either central VRF or multi splits. i have the running currents etc, but he wants to know the "average" time the compressor will be running.

As the title says, how long is a piece of string, any ideas very roughly.

Thanks