Title 24 Separation of Electrical Circuits
The distribution system has to be designed so measurement devices can monitor load types separately — lighting, HVAC, plug loads and EV charging. Nothing is required at 50 kVA or below; above 250 kVA lighting and HVAC must be disaggregated in detail.
A design requirement, not a metering one
Read the wording carefully: the system must be designed so that measurement devices can monitor the usage of load types. It is about how circuits are arranged, not about installing a particular meter.
That distinction is what makes this expensive to retrofit and nearly free to design in. Once lighting and mechanical loads share a panel, separating them later means rewiring. Deciding at design stage that they will not share is a drawing decision.
Four load types, each on its own ladder
The requirement scales by service size, and not uniformly:
- Lighting — nothing at 50 kVA or below, up to disaggregation by floor, type and area above 250 kVA
- HVAC — nothing at 50 kVA or below, up to every load of 50 kVA or more monitored separately above 250 kVA
- Plug loads — nothing at 50 kVA or below, separated by floor, type and area only above 1000 kVA
- EV charging stations — all loads in aggregate, at every service size
EV charging is the one to notice. It is the only load type with no size threshold at all — even the smallest service must be able to see its EV charging in aggregate. That reflects how quickly EV load can come to dominate a building's profile, and how separately it needs to be understood from everything else.
The 10 per cent tolerance
Up to 10 per cent of connected load may be of mixed type. This is a practical allowance rather than a loophole: in any real building a handful of circuits serve genuinely mixed loads, and forcing absolute purity would mean panels full of near-empty breakers.
Ten per cent is enough for the awkward cases and not enough to avoid the requirement, which is what a well-set tolerance looks like.
Healthcare is exempt, twice over
Healthcare facilities are exempt, and so are systems subject to California Electrical Code Article 517. Both exemptions point the same way — where electrical design is governed by patient safety, energy monitoring does not get to reorganise it.
Why this is a coordination requirement
Nothing here is visible in the architecture, and nothing is decided by the energy consultant. The panel schedule and the single-line diagram determine compliance. A project where the electrical engineer never sees this requirement will produce a distribution design that cannot satisfy it, and the discovery will come after the panels are specified.