Before switching to a time-of-use electricity rate, download at least 12 months of interval usage and price each interval under both plans. Add fixed charges, seasonal rates, demand charges, taxes, and enrollment costs. Then model only the loads you can realistically move. A cheap overnight rate can lose money when cooling, cooking, or heating remains in an expensive peak window.
Recent EV and frugal discussions show both savings and regret. The recurring failure is comparing only the cheapest advertised rate instead of repricing the household full load profile.
Start here: a practical action plan
- Download a year of interval data.
- Price every interval under both plans.
- Model only realistic shifts and all fees.
- Audit actual savings after a full season.
- Comparing only the cheapest rate.
- Ignoring expensive cooling or cooking hours.
- Leaving timers on an outdated schedule.
Price the existing load before changing behavior
Download hourly or finer interval data from the utility when available. Mark each interval peak, off-peak, or super-off-peak under the proposed schedule. Include weekends, holidays, seasons, and critical-peak events exactly as the tariff defines them.
Calculate a baseline using current behavior. Multiply kilowatt-hours in each window by its energy rate, then add fixed customer charges, riders, delivery, taxes, and any meter or program fee. Compare the same billing components under the flat plan.
Worked example: cheap nights still lose
Example: a month uses 900 kilowatt-hours. Under a flat 18-cent rate, energy cost is $162. Under time-of-use, 300 peak kilowatt-hours at 35 cents cost $105 and 600 off-peak kilowatt-hours at 10 cents cost $60, totaling $165.
The time-of-use energy portion is $3 higher before fees. If 100 kilowatt-hours can move from peak to off-peak, savings are 100 × ($0.35 - $0.10) = $25, making the modeled energy cost $140. The household must actually shift that usage.
| Hypothetical monthly plan | Calculation | Energy cost |
|---|---|---|
| Flat rate | 900 × $0.18 | $162 |
| TOU peak | 300 × $0.35 | $105 |
| TOU off-peak | 600 × $0.10 | $60 |
| TOU before shifting | $105 + $60 | $165 |
Model movable loads conservatively
Identify movable loads from EV charging, dishwashing, laundry, water heating, pool pumps, or pre-cooling where safe and practical. Do not assume essential medical equipment, cooking, or extreme-weather heating can move. Account for household routines and appliance safety.
Check setup costs and lock-in. A special meter, electrician work, program fee, early-exit rule, or higher demand charge can erase modest energy savings. Divide one-time cost by conservative monthly savings to estimate a break-even period.
Review after the first full season
After enrollment, compare each bill with the counterfactual flat-rate calculation using actual interval use. One mild month is not proof. Evaluate at least the expensive season and confirm that automation did not drift into peak hours.
Retest when rates, peak windows, household schedules, EV mileage, heating equipment, or solar change. Keep the original data and spreadsheet so the decision can be reversed based on evidence rather than memory.
- Download a full year of interval data.
- Price every interval under both tariffs.
- Model only realistic load shifts and all fees.
- Audit actual savings after a full season.
Frequently asked questions
Does time-of-use pricing always save money?
No. Savings depend on the full usage profile, rate windows, fees, and how much load can move.
How much data should I use?
Use at least 12 months when available so heating, cooling, and seasonal rates are represented.
What is the break-even shift?
It is the peak usage that must move to cheaper hours to offset any higher costs and fees.
Should I count only EV charging?
No. Reprice every household interval because higher peak rates apply to other loads too.
Do fixed charges matter?
Yes. Include program fees, meter costs, delivery, taxes, and demand charges that differ.
When should I review the switch?
Review monthly and after the first expensive season, then whenever rates or household loads change.
Sources and review notes
The calculations and scenarios in this guide are original BreadWinnr worked examples. We recalculated each example and checked that its parts match the stated total. Official sources support the financial concepts. Forum links document the reader problem that prompted the guide and are not treated as financial authority.
- U.S. Department of Energy: Estimate appliance energy use
- Forum discussion: recent TOU savings and losses
- Forum discussion: TOU plan tradeoffs
Read our research, testing, corrections, and source policy.
This guide provides general financial education. It does not account for your complete financial, tax, legal, or contractual situation.
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