Dear Antone,Good ...

Dear Antone,

Good question,

Electricity consumption depends on raw water quality (individual ions concentration) Reverse osmosis system design (system recovery rate, number of stages, type of membranes, etc.) and operating conditions (water temperature). 

You can use Reverse osmosis design simulator to estimate electricity consumption. It is not an accurate result but will give you a very good idea, and making some tries in different conditions will precise the results. No electricity consumption result from another system will be exactly the same as yours. The reasons are that:  they don't have same water quality, same pumping equipment’s and same type of system (in term of design) as yours.

Some roughly idea

The theoretical absolute minimum amount of  energy  required by natural osmosis to desalinate average seawater is approximately 1 kilowatt-hour per cubic meter (kwh/m3) of water produced, or 3.8 kilowatt-hours per thousand gallons (kwh/kgal).

1. The RO process consumes 2.9 kWh/m3 to 3.2 kWh/m3for normal water
2. 2.2 kWh per cubic meter to 6.3 kWh per cubic meter in desalination,
3. For large plant The total consumption is 3.6 kWh/m3,

The power consumption also depends upon membrane condition