Definition
Time-of-Use electricity pricing (Time-of-Use Tariff, TOU, billing by time period) is a billing method that divides electricity prices by usage periods. Typically, one day is divided into peak, flat, and off-peak periods (e.g., peak 8:00-12:00, 18:00-21:00; off-peak 23:00-7:00), with higher prices during peak periods and lower prices during off-peak periods. Price signals guide users to shift loads such as charging, production, and air conditioning to off-peak periods, achieving peak shaving and valley filling, reducing grid peak pressure and users' electricity costs.
Time-of-Use electricity pricing is an important tool for demand-side management. When combined with orderly charging, energy storage, and demand-side response, it can effectively regulate the load curve. Some regions also implement more detailed pricing mechanisms such as super-peak and deep-valley tariffs.
Technical Features
Time-of-use electricity pricing relies on smart meters to measure consumption by time period. Smart meters collect time-of-use electricity data through protocols like DLMS/COSEM and 645, then transmit it via collectors and concentrators using IoT SIM cards to the cloud platform, supporting time-of-use billing and settlement. Charging stations and energy storage can automatically or manually select charging/discharging times based on time-of-use pricing.
Use Cases
Time-of-use electricity pricing is widely used in residential electricity, industrial and commercial electricity, charging stations, energy storage, data centers, and other scenarios. Smart meters support time-of-use billing; orderly charging and charging stations guide users to charge during off-peak periods based on time-of-use pricing. SimtoLink provides stable connectivity and dedicated APN for smart meters, charging stations, and other devices, supporting time-of-use billing and load scheduling.
Rate registers and frozen readings
Time-of-use pricing shows up in the meter as a set of active-energy registers accumulated by rate number. Peak, flat, and off-peak, and in some regions a critical peak and a deep valley, each keep a forward-consumption reading and a reverse-export reading. The smart meter follows only the rate table it stores, and at each period boundary it adds later energy into the next set of registers. A cyclic report over the IoT SIM should include the meter address, rate number, reading, freeze time, and meter clock, so the master station can subtract two successive freezes and get that interval's energy. If the only value sent is a current total active energy, the platform cannot see the peak-valley split, and settlement still has to read the time-of-use readings inside the meter.
The rate table also sets the seasonal changeover dates, whether weekends use a separate table, and which table statutory holidays follow. Those dates come from the catalog published by the supply company and are downloaded to the meter or the collector. Which register is active depends on the clock inside the meter. Time the module takes from the network can stamp an uplink and show that a report is late, but it does not replace the meter's own clock. Once the two clocks differ across a period boundary, the same kilowatt-hour falls into neighboring rates on the meter and on the platform. Forward and reverse have to be configured separately. When storage exports to the grid in an off-peak period, that energy should enter the reverse rate. If only the forward registers are enabled, export energy has nowhere to be written.
Which schedule the load equipment follows
A charger, a storage converter, or a controllable air conditioner can act on a time-of-use tariff only when that metering point is already settled by time of use. A customer still billed on a single rate, or assessed only on maximum demand, does not change the bill by copying in an outside peak-valley clock. The schedule stored in the device has to be the same version as the settlement meter, including whether today is a critical-peak day. Hard-coding 23:00 to 07:00 the next day in firmware puts the charge and discharge window opposite the real price as soon as the seasonal table or a critical-peak day changes. The power-limit window sent by orderly charging should be built from the rate table in effect that day. Projecting tonight's off-peak from last month's frozen energy misses a change that has already been published.
After a period switches, the uplink has to deliver the frozen reading to the collection master. Directed access or a private APN sends the message to the assigned master and cuts the chance that a firewall drops it because the address changed. Time-of-use reading messages are short. If the same SIM is also uploading a one-second load curve, the reading sits behind the curve once the channel is full, and the first freeze after the switch arrives late. A demand sliding window and time-of-use energy are different quantities. Demand is the peak of short-interval average power, and it cannot be written into one rate's energy register. Meter protocols on the collection side are common; what matters is reading each rate freeze by its data identifier, rather than reading only total energy.
Field reasons a rate is booked the wrong way
When the meter's time zone or daylight-saving setting does not match the settlement time zone, every period shifts together. Peak energy appears as a block on the off-peak bill, and reconciliation finds no missing numbers. If the holiday table was never downloaded, a statutory holiday still accumulates on the weekday peak, while the customer has already moved load into the daytime and the meter still prices it as peak. After the platform sees that the meter is running slow, slicing historical readings again with server time reallocates energy already written into the registers and leaves an adjustment that cannot be matched to the readings in the meter.
While the collection link is down, the meter keeps accumulating locally by rate. If recovery backfills only the current total reading and not the freeze record for each rate, every interval during the outage loses its basis. When one collector serves several meters, a swapped meter address books meter A's off-peak reading under meter B. Used together with peak-valley scheduling, a dispatch order that takes effect off the rate boundary means the load has already moved while the energy is still in the peak register, so the dispatch log and the bill do not match. When the master poll is longer than a rate period, increments from two rates merge into one reading and cannot be split afterward.