Time-of-use tariffs: calculate a shift before expecting a saving
Copy the current tariff first
EIA explains that electricity prices reflect multiple factors. A time-of-use tariff sets rates for specified periods, but the periods and other charges come from the actual supplier terms. Do not substitute another region’s peak window. Record the tariff edition, time zone, weekday rules, seasons and whether holidays use different periods.
Fields for a bill comparison
| Field | Record |
|---|---|
| Energy | kWh in each period multiplied by that period’s rate |
| Fixed charges | Daily or monthly charges and relevant fees |
| Demand | Any maximum-power charge and measurement interval |
| Other terms | Taxes, credits, minimum charges or programme conditions |
| Constraints | Comfort, charging deadlines and equipment instructions |
A fictional shift of ten kilowatt-hours
Moving 10 kWh from a fictional rate of 0.30 to 0.10 currency units per kWh reduces that energy component by 10 × (0.30 − 0.10) = 2 units. It does not establish the total bill saving if the new plan changes fixed charges or adds a demand charge. If the later operation consumes an extra 3 kWh at 0.10, that adds 0.30 units; state the extra use rather than assuming an identical load.
Apply the comparison to an actual interval record where one is available. A monthly total alone cannot show which hours can move. Avoid moving loads in a way that violates equipment instructions or creates an unsafe indoor condition.
Test the assumption against a full bill
Keep the old and new bill periods comparable and note changes in weather, occupancy or equipment. Separate the calculated rate effect from measured total consumption. Treat an unexplained discrepancy as a reason to check terms and readings, not proof that the supplier used the wrong rate. We have not inspected any reader’s bill or forecast a saving.
Sources and scope
- US EIA: electricity prices and affecting factors — General price context; the actual supplier tariff determines the bill.
Sources checked October 10, 2026. AI-assisted research and drafting. The examples, calculations and worksheets are Luminesca editorial work; they are not measured trials, first-hand reporting or an independent certification. Removed universal savings claims and assumptions that every tariff follows the same peak hours. Report a specific correction with its source.