Submetering for Multifamily Buildings

What to measure

Per-unit electric, water or thermal consumption is the billing layer. Common-area load — corridor and garage lighting, elevators, amenity spaces, pumps, central heating and cooling plant — is the operating layer, and it is usually where the recoverable savings live.

The gap between the master meter and the sum of unit meters is itself a diagnostic. A widening gap points to common-area growth, a leak, or a meter that has stopped reporting.

• Per-unit electric, water and/or BTU metering at billable accuracy
• Common-area electric and water as distinct measurement points
• Central plant heating and cooling energy where units are served from a loop
• Master meter reconciliation against the sum of submeters
• Leak detection on risers, laundry and irrigation

Which hardware fits

For anything that will appear on a resident's bill, use meters built for billing: encoded or pulse-output water meters and revenue-grade electric meters, installed so the serial number, location and unit assignment are documented at commissioning. Regulators and residents both ask the same question — which meter served which apartment, and can you prove it.

Retrofits favour wireless AMR: battery-powered radio or LoRaWAN reads avoid opening walls or entering units for readings, and a single gateway typically covers a building.

• Encoded/AMR water meters for per-unit consumption
• Revenue-grade electric submeters for unit and common-area circuits
• BTU meters for units served by a central hot or chilled water loop
• LoRaWAN or cellular gateways for automatic reads without unit access

Compliance and billing

Tenant billing rules are state and city specific. Several jurisdictions require particular meter accuracy classes, disclosure of billing methodology, and retention of underlying interval data; others restrict what may be charged above the utility rate. New York's Local Law 88 tenant submetering requirements and Pennsylvania's rules on billing residents from submeter data are the two we are asked about most, and both reward getting the meter and record design right before the first invoice.

Building performance standards and benchmarking ordinances draw on the same dataset, which is a good reason to design the common-area metering to benchmarking granularity rather than the minimum the billing rule requires.