Best Practices, Consulting Services, Solar Electric Power
Smart Tariffs, Smarter Homes
Oct
From Time-of-Use Tariffs to a Home That Responds for You
Smart meters, solar export credits and home energy-management systems can help households choose when to charge an EV, heat water, run large appliances, store solar energy or export it when the feed-in value is high.
The central principle
A smart meter is primarily a secure revenue-metering device. It records electricity imported from the grid and solar electricity exported to the grid, including the time at which the flow occurs. A home energy-management system, or HEMS, uses that information with tariff data and household preferences to control compatible appliances.
What the smart meter does
- Measures separate import and export energy in kWh
- Records time-of-use periods and interval energy data
- Supports prepaid billing and solar export-credit settlement
- Provides verified records for the electricity bill
- Can provide authorised near-real-time energy information
What the HEMS does
- Reads electricity prices and solar export credits
- Monitors PV generation, battery state and household demand
- Schedules EV charging and flexible appliances
- Protects comfort, mobility and backup-power requirements
- Lets the customer override automation at any time
How the system works
The smart meter remains the source of truth for billing. The HEMS uses forward-looking tariff information and real-time household conditions to decide whether a flexible load should run, pause, charge or wait.
HEMS tariff-response animation
The interactive example below shows how a HEMS can compare future import costs with present feed-in credits. It selects between charging an EV from rooftop PV, pausing flexible demand to export solar, resuming charging, or waiting for a lower-cost period.
Solar, EV and tariff decision simulator
Choose a scenario or press play. The HEMS does not merely follow price: it preserves the customer’s EV departure requirement, battery reserve, critical loads and manual override.
Charge the EV from solar surplus
The current export credit is low relative to the later avoided import cost. The HEMS uses available PV surplus to charge the EV while preserving the customer’s charging deadline.
Customer rules always remain in force
The revenue meter remains the authoritative source for import and export settlement. The HEMS uses tariff data and customer-approved automation to manage compatible household devices.
Useful technology standards
Different standards address different parts of the system. A municipality or supplier should avoid forcing customers into a closed appliance-control ecosystem. The meter, tariff platform, HEMS, inverter and EV charger can be interoperable while still serving distinct functions.
| System layer | Relevant standards or interface | Function |
|---|---|---|
| Smart metering and prepayment | NRS 049, IEC 62056 DLMS/COSEM, IEC 62055 STS | Revenue metering, import/export registers, tariff configuration and prepaid settlement |
| Tariff and flexibility signals | OpenADR, REST API, MQTT or structured tariff file | Current and future electricity prices, export credits and demand-response events |
| PV, battery and inverter control | IEEE 2030.5, SunSpec Modbus or approved inverter API | DER monitoring, operating status, capability and coordinated control |
| EV charging | OCPP and ISO 15118 | Charging schedules, power limits and communication between charging equipment and EVs |
| Home appliances | Matter, Zigbee, Wi-Fi, KNX, Modbus or manufacturer API | Local control of compatible appliances, geysers, pumps and smart plugs |
What tariff providers should publish
A dynamic or time-differentiated tariff is only fair when customers can see it and respond to it. The tariff programme should therefore include data access and customer safeguards—not merely a revised list of R/kWh charges.
- Time-of-use calendar: peak, standard and off-peak periods; seasons; weekends; public holidays; effective date; and version number.
- Separate import and export prices: households should see both the price paid for imports and the credit received for exported PV.
- Machine-readable tariff data: provide a documented API, MQTT service, CSV/JSON file or comparable digital interface that a customer-authorised HEMS can access.
- Forward prices: dynamic tariffs should make next-day or future interval prices available early enough for EV and battery scheduling.
- Interval-level settlement data: customers need access to imports, exports, tariff periods and the tariff version used for billing and export-credit settlement.
- Consumer protections: manual override, informed consent, critical-load exclusions, privacy safeguards and a clear route for queries or disputes.
A smart tariff should be a useful customer signal
Smart meters and time-of-use tariffs can help households lower costs, use more rooftop solar locally and support a more flexible electricity system. They work best when the customer receives the price signal electronically, can connect their chosen HEMS, and remains in control of household priorities.
Bidirectional smart meter + interval settlement data + machine-readable tariff signal + customer-controlled HEMS + compatible EV charger, battery, inverter and appliances.
