"How many submeters do I need?" is the first question almost every building owner asks — and the honest answer is: it depends on what you are trying to accomplish. Meter too little and you cannot satisfy code or isolate a problem; meter every circuit and you blow the budget on data nobody uses. This framework gets you to the right number.
Start With the Driver, Not the Panel
Before counting circuits, name the goal. Code compliance, tenant billing, operational fault detection, and incentive documentation each demand a different metering density. Most projects have two or three drivers at once, so list them in priority order — that list dictates where meters go.
Driver 1 — Code Compliance
If a code applies, it sets your floor. IECC 2024 generally requires measurement by load category for buildings 10,000 square feet and larger; ASHRAE 90.1 Section 8.4.3 calls for end-use monitoring (total, HVAC, interior lighting, exterior lighting, and other) at the 25,000-square-foot threshold. Start by mapping your loads to whichever categories your jurisdiction enforces — that mapping is the minimum meter count.
Driver 2 — Tenant Billing and Cost Allocation
If you bill or allocate cost, you need one revenue-grade metering point per billable entity — per tenant, suite, or department. This is usually the largest single driver of meter count in multi-tenant buildings, and it is non-negotiable: you cannot fairly bill a load you do not measure.
Driver 3 — Operational Visibility
Beyond compliance and billing, the question becomes diminishing returns. Metering your largest and most variable loads — HVAC, chillers, major process equipment, EV charging — captures most of the savings opportunity. Metering every small lighting branch rarely pays for itself. A practical rule: meter loads that are large, variable, or suspect, and aggregate the rest.
A Simple Counting Method
Walk it in order. Count one point per code-required load category. Add one revenue-grade point per billable tenant or department. Add points for your top energy-consuming and most variable systems. Then stop, and let everything else roll into an "other/miscellaneous" bucket. The sum is your target meter count — and you will usually find the same physical meter can serve more than one driver.
Don't Forget Channels vs. Meters
Modern branch-circuit power monitors measure many circuits from a single device. So "how many submeters" is really "how many metering points (channels)," not how many boxes on the wall. A single multi-circuit monitor can cover an entire panel, which changes the cost math dramatically versus discrete meters.
Common Mistakes
Two errors dominate. The first is metering for code only, then discovering you cannot bill tenants or find faults. The second is over-instrumenting — putting revenue-grade meters on loads that only need trend data. Both waste money. Design once, to the full priority list, and right-size accuracy per point.
The right number of submeters is the number that satisfies your highest-priority drivers without paying for data you will never act on. Map your drivers, count by category, and let multi-circuit monitors do the heavy lifting.