The formula to calculate cost from wattage, quantity, efficiency, electricity cost, and hours is:

\[ \text{Cost} = \left( \frac{\text{Wattage}}{\text{Efficiency}} \right) \times \text{Quantity} \times \frac{1}{1000} \times \text{Electricity Cost} (\$/kWh) \times \text{Hours} \]

Where:

• \(\text{Cost}\) is the total electricity cost.
• \(\text{Wattage}\) is the power consumption in watts.
• \(\text{Quantity}\) is the number of units.
• \(\text{Efficiency}\) is the efficiency factor (default is 0.92).
• \(\text{Electricity Cost}\) is the cost of electricity in dollars per kilowatt-hour.
• \(\text{Hours}\) is the number of hours the lights are used.