A ventilation fan is running 24 hours/day with a 4.0kW motor.  An SMV IP65 inverter is fitted, charged at list price.  The running speed is reduced to 80%.

Based on electricity costs of 8p/kWhr, how many days does it take to recover the costs of the inverter?

All you need to do is write your answer on your business card and put it in the bowl on our stand.

(Hint: the answer is between 100 and 730)