Common use of Duty cycle Clause in Contracts

Duty cycle. Model Average Hours of Operation/Day Model 1 1 Light 3-4 Hours. Model 2 2 Lights, 3-4 Hours. Model 3 1 Light, 1-2 hours, 1 Fan- 1-2 hours. Model 4 2 Lights, 2-3 hours, 1 Fan- 2-3 hours. Model 5 4 Lights, 3-4 hours.