What are formula meters and what types are available?

Formula meters are virtual meters that calculate values from one or more physical (source) meters. They do not have hardware — they compute consumption based on a formula you define.

Five formula types

1. Sum — Adds consumption from multiple source meters. Use when you want a combined total that no single physical meter measures. Example: Total tenant electricity = Tenant A + Tenant B + Tenant C.

2. Difference — Subtracts child meters from a parent meter. Use when you need the delta between a main meter and its sub-meters. Example: Main meter minus (Sub 1 + Sub 2) = unaccounted consumption.

3. Ratio — Calculates a proportional relationship between meters using weights. Use for cost allocation ratios or proportional splits. Each source meter has a configurable weight multiplier (default 1.0).

4. Rest Usage — A specialized difference formula: Main meter minus all specified child meters. Designed for the common case of finding unmeasured or unallocated building consumption. Requires selecting a main meter and one or more child meters to subtract.

5. Custom — A free-form mathematical expression referencing meter values. Example: "meter_a + meter_b * 0.5". The system validates custom formulas before saving. Use for complex calculations that do not fit the standard types.

Key fields

• Name: Descriptive label for the formula meter
• Building: The building this formula applies to
• Unit: Measurement unit (e.g., kWh, m3) — must match source meters
• Decimal Places: Precision for calculated values (0-10, default 2)
• Source Meters: Physical meters used in the calculation

Where to manage: Analytics → Formula Meters. Use the "Create Formula Meter" button or the quick actions "Create Sum" and "Create Rest Usage" for common patterns.