Title 24 Service Electrical Metering Requirements
Every electrical service or feeder needs a permanently installed metering system. What it must measure scales with service size — instantaneous kW demand at any size, historical peak demand from 250 kVA, and kWh by rate period from 1000 kVA.
Permanently installed, not portable
The requirement is for a metering system that is permanently installed. A clamp meter brought out for a survey does not satisfy it — the building has to be able to report its own consumption continuously, without anyone visiting.
That is the whole intent of the section. You cannot manage what you cannot see, and a building with no instrumentation is invisible to its own operator.
Four capabilities, three thresholds
The requirement steps up with service size:
- Instantaneous kW demand — every service size, no exceptions by size
- Tracking kWh for user-definable periods — every service size
- Historical peak demand — from 250 kVA and above
- kWh by rate period — only at 1000 kVA and above
The progression follows what an operator at each scale can actually act on. A small building needs to know what it is drawing now and over a period it chooses. A larger one needs peak history, because demand charges are set by peaks. A very large one needs consumption split by rate period, because that is how its tariff is structured.
The utility meter can satisfy it
There is an exception where the utility company provides a metering system that indicates instantaneous kW demand and kWh for a utility-defined period. Where that is in place, the service does not need a second meter.
This is worth checking before specifying anything, because it can remove the requirement entirely for a straightforward service. It is also worth confirming rather than assuming — the exception is specific about what the utility meter has to indicate.
Article 517 systems are out
Electrical power distribution systems subject to California Electrical Code Article 517 are excepted. Article 517 covers health care facilities, where the electrical design is governed by patient safety requirements that take precedence.
Where kVA is decided
Because every threshold here is a service size in kVA, the metering scope is set by the electrical design rather than by anything the energy consultant controls. A service sized at 250 kVA and one sized at 240 carry different obligations.
That makes this a coordination item. The person who knows the service size and the person producing the compliance documents are usually not the same, and the requirement is invisible from the architecture.