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Rates & tariffs

TOU period misapplication

Time-of-use usage is split into the wrong on-peak and off-peak hours because of a stale meter program, daylight saving time or holiday errors.

How often we find it
Found on roughly 1 in 18 time-of-use accounts we audit
Typical impact
2% to 10% of energy charges on the affected account

Time-of-use (TOU) schedules price energy, and sometimes demand, differently by hour, day type and season. The tariff defines each period in local time: for example, on-peak from 4 pm to 9 pm on weekdays, with listed holidays treated as off-peak. Many utilities have moved their on-peak windows later in the day over the past decade as solar generation shifted system peaks. Billing a TOU account correctly depends on the meter or the billing system assigning each interval to the right period. Errors appear when a meter keeps an old program after a rate case moves the window, when a meter clock is not adjusted for daylight saving time so every period shifts one hour for most of the year, when holidays are billed as weekdays, or when the season boundary falls on the wrong date. Because the energy total is still correct, the error is invisible on a bill unless someone recomputes the period split from interval data.

How it happens

  • A rate case moved the on-peak window, but the meter or billing system kept the old period definitions.
  • The meter clock runs on standard time year-round, so during daylight saving time every period boundary is off by one hour.
  • Tariff holidays are billed as weekdays, or the holiday list is outdated.
  • The summer and winter season boundaries are applied on the wrong dates, or a bill spanning the boundary is not prorated.
  • A new TOU schedule was assigned without reprogramming a meter that records periods internally.

How to detect it

  • Rebuild on-peak, mid-peak and off-peak kWh from 15-minute interval data using the tariff's current period definitions, and compare to the bill.
  • Check the one-hour shift between March and November, which points to a daylight saving time problem.
  • Confirm that tariff holidays are billed as off-peak.
  • Compare period definitions on the bill (if printed) to the tariff sheet effective dates.

Evidence the utility will accept

  • 15-minute interval data for the claim period
  • The tariff sheets defining TOU periods, seasons and holidays, with effective dates
  • Bills showing kWh by TOU period
  • A recomputed period split by month

Recovering the overcharge

We file a dispute with the recomputed period split, the tariff's effective period definitions and the interval data, and request rebilling for each affected month within the back-billing window. We also ask the utility to reprogram the meter or correct the billing system so future bills are right. Utilities generally resolve these once the interval-based recomputation matches their own data.

Questions we get asked

Yes. A shifted window can move usage either way, depending on your load shape. We recompute every month and file only where the net result favors you, and we tell you about the rest.

Less often, because many utilities apply periods in the billing system from interval data. Errors still occur when the system's period table or holiday list is not updated after a rate case.

Tariffs define periods in local time. A meter left on standard time shifts every boundary by an hour for about eight months a year, which matters when load ramps sharply at a period boundary.

Find this error in your own bills.

Connect bills for up to 50 meters. Get the findings report in about three weeks. Pay nothing unless money comes back.

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from bill access to first findings report
21 daysfrom bill access to first findings report
of filed claims accepted by the utility in full or in part
94%of filed claims accepted by the utility in full or in part