How time-of-use electricity pricing changes your costs
Moving a task to a cheaper hour can reduce its energy charge without reducing its kWh. The saving depends on when electricity is drawn, which may differ from when you start the appliance.
Build the bill from rate windows
Read the schedule for weekdays, weekends, holidays and seasons. Use the supplier’s clock and interval definitions. Group consumption into the applicable windows. Energy charge equals the sum of each window’s kWh multiplied by its price per kWh. Fixed fees and any demand charges need separate treatment.
A load shift with a measurable limit
Suppose a fictional USD tariff charges 0.36/kWh at peak and 0.14/kWh off-peak. A month with 90 peak kWh and 210 off-peak kWh costs 32.40 + 29.40 = USD 61.80 before fees. Moving 30 kWh to off-peak gives 60 × 0.36 + 240 × 0.14 = USD 55.20. The USD 6.60 saving equals 30 × (0.36 − 0.14). Consumption remains 300 kWh.
Follow the load through the whole cycle
A tank may reheat after a shower ends. A dishwasher can draw energy in several stages and cross a price boundary. Allocate the energy, rather than assigning every kWh to the start hour. Keep manufacturer operating instructions and household needs in the decision.
Run the Bill Calculator once per window with zero fees and tax, then sum the energy charges. Add the account fee once and apply the supplier’s tax rules separately. The calculator does not assign timestamps. Before changing plans, price a full year under both schedules, including different fixed fees. A few shifted loads cannot establish that the whole plan is cheaper.
Electricity & Water Bill Calculator
Worked example: Budget electric hot water across two rate windows
Related reading: Reading electricity interval data without confusing kW and kWh
Reference: EIA: electricity prices and time-based pricing.