Question: how to calculate electricity cost per watt?
Answer: kWh = P(W) × T(h/day) ÷ 1,000(W) kWh = 400 W × 4 hrs ÷ 1,000. kWh = 1.6 kWh.
Price = Electricity(kWh) × Cost(cost/kWh) Price = 1.6 kWh × $.12. Price = $.19 per day.
Monthly Price = $.19 per day × 30. Monthly Price = $5.70.