Time-of-Use Savings Calculator
Compare the energy charge for the same shiftable kWh at peak and off-peak rates. Use the exact tariff periods and variable charges on your bill; a time-of-use plan is not automatically cheaper.
Quick answerShifting 5 kWh/day from $0.30/kWh peak pricing to $0.12/kWh off-peak pricing saves $0.90 per active day. Across 365 days, the modeled energy-charge saving is $328.50, reducing that shifted energy from $547.50 to $219.00.
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Your details
Results
A negative result means the entered off-peak rate is higher.
Annual modeled saving divided by 12.
Measure load timing before automating a schedule
Interval data can show when energy is used. Use only controls approved for the exact load, and compare the complete tariff before changing plans.
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Amazon opens in a new tab. Use built-in scheduling where available. A smart plug is only for compatible plug-in loads within every rating and instruction—never heaters, hardwired appliances, EV charging or other high-power equipment.
How it works
Shifted annual energy = kWh per active day × active days. Peak cost = annual shifted energy × peak rate. Off-peak cost = the same energy × off-peak rate. Annual saving = shifted energy × (peak rate − off-peak rate), and average monthly saving = annual saving ÷ 12. The calculation excludes rate-plan changes outside those kWh, demand charges, fixed charges, taxes, behavioral rebound and any efficiency change caused by a different schedule.
Time-of-use shifting scenarios
Each row moves the same amount of energy from one entered rate to another; it does not compare the rest of the household tariff.
| Shifted energy | Rate change | Annual saving |
|---|---|---|
| 1 kWh/day × 365 days | $0.25 → $0.15 | $36.50 |
| 5 kWh/day × 365 days | $0.30 → $0.12 | $328.50 |
| 10 kWh/day × 250 days | $0.40 → $0.15 | $625.00 |
| 20 kWh/day × 200 days | $0.35 → $0.10 | $1,000.00 |
| 5 kWh/day × 120 days | $0.45 → $0.20 | $150.00 |
| 5 kWh/day × 365 days | $0.12 → $0.20 | −$146.00 |
Tariffs may vary by season, weekday, holiday or critical event. Model each applicable block separately and compare the complete annual bill before changing plans.
Worked example: five kWh shifted every day
The rate difference is $0.30 − $0.12 = $0.18/kWh. Daily saving = 5 × $0.18 = $0.90. Annual shifted energy is 5 × 365 = 1,825 kWh. At the peak rate it costs $547.50; at the off-peak rate it costs $219, a difference of $328.50 or $27.38 per average month.
This assumes total kWh stays unchanged. Charging losses, preheating, thermal losses or different equipment behavior can change total energy when the schedule changes.
Compare the whole tariff, not one price gap
DOE separates energy charges, demand charges and fixed charges. A time-of-use plan may also change shoulder rates, weekends, seasons, critical-event prices, minimum bills or credits. Saving on one shifted block does not prove the alternative plan lowers the complete bill.
Reprice at least a representative year of interval data under both complete tariffs where possible. EIA explains that its published average retail prices are not the tariff rates charged to an individual customer.
Use interval data to find genuinely shiftable kWh
DOE notes that advanced meters often provide hourly or 15-minute interval data. Use that pattern to separate flexible loads from unavoidable peak use. EV charging, thermal storage and some appliance cycles may be flexible when manufacturer and safety requirements allow.
Do not count the same kWh twice across overlapping actions. A battery also has round-trip losses and capital cost, while moving heating or cooling can change total energy through building heat loss.
Demand charges need a different model
A demand charge is based on maximum kW under tariff-specific measurement windows, not total shifted kWh. Moving energy can reduce, preserve or create a demand peak depending on how loads overlap. This calculator covers only variable energy charges.
Commercial tariffs can include non-coincident peaks, time-of-use demand windows, ratchets and minimum requirements. Use the exact tariff and interval-demand data for those cases.
Schedule equipment through approved controls
Use built-in timers, vehicle or charger scheduling, utility programs or controls approved for the exact load. Do not add a generic smart plug to a heater, hardwired appliance, EV charger or other high-power equipment. Preserve food safety, water sanitation, battery limits, pool requirements and comfort or health needs.
Critical-peak events and daylight-saving transitions can also change clock periods. Confirm the utility’s current calendar and device time settings.
Sources used for assumptions: U.S. Department of Energy — utility rate options, interval data and bill components; U.S. Department of Energy — demand response and time-variable pricing programs; U.S. Energy Information Administration — time-of-day pricing and peak demand context; U.S. Energy Information Administration — why average prices are not individual tariff rates.
Frequently asked questions
How do I calculate time-of-use savings?
Multiply shifted kWh by the difference between the old and new variable rates, then by the number of active days. Compare the full tariffs separately.
Is a time-of-use tariff always cheaper?
No. It depends on the complete rate schedule and your load shape. Higher peak or shoulder charges can outweigh savings from off-peak use.
What electricity use can be shifted?
Only loads that can safely and practically move while meeting equipment and household requirements. Use interval data and approved scheduling controls to identify them.
Does the calculator include fixed charges?
No. Fixed charges usually do not change with shifted kWh, but they still belong in a complete tariff comparison.
Does it include demand charges?
No. Demand charges depend on maximum kW and tariff-specific windows or ratchets, so they require interval-demand analysis.
What if the off-peak rate is higher?
The result becomes negative, correctly showing an added energy charge rather than a saving.
Should I use a smart plug to shift appliances?
Only when the appliance and control manufacturers permit the exact setup and all voltage, current, startup, safety and local requirements are satisfied. Never assume a generic plug is suitable for heaters or high-power equipment.
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