# How to calculate the slowness and fastness of energy meter if we have different kw load for example (0.746 kw and meter rev constant 400 and we calculate the 2 rev in 30 sec) and explain the formula ?

- Meter rev constant means rev/ kwh.

Then one rotation = 60x60/400 or 9kws.

2 rotations = 18kws.

Time taken is 30s.

Then the av load is 18/ 30 or 0.6 kw.

To calculate whether this Energy Meter is slow or fast using this formula.

Slowness/Fastness=Tcâˆ’To/To X 100