The plant's electrical input divided by its cooling output — kW drawn per ton of cooling delivered, the standard measure of how efficiently a chilled-water plant runs. A rising kW/ton against the plant's own design is the clearest efficiency-drift signal: fouled tubes, low flow, or a plant staged poorly for the load. A monitoring metric — Keedian reports and alarms on drift; it does not control the plant.
How much electrical power the chilled-water plant draws to deliver a unit of cooling — kilowatts of plant input per ton of cooling output. Scoped to the plant equipment being metered (chillers, and the chilled-water pumps, condenser-water pumps, and tower fans included in the meter boundary), it is the single number that says whether the plant is producing cooling efficiently, trended against the plant's own design and commissioning figure.
Cooling output in tons is derived from chilled-water flow and the evaporator ΔT — tons = flow (gpm) × ΔT (°F) ÷ 24 for water — so the metric requires both a chilled-water flow measurement and the supply/return temperatures that Cooling ΔT already uses.
Efficiency is the metered electrical input over that output — kW/ton = plant kW ÷ tons — computed only over intervals with the plant actively producing cooling and with valid flow and power readings. The meter boundary (chiller-only vs full plant including pumps and tower fans) is fixed per plant so the figure is compared like-for-like over time.
The metric is trended against the plant's own design / commissioned kW/ton, never an invented cross-plant benchmark. It is read from metering only — Keedian reports the drift and can alarm on it, but staging, reset, and any efficiency correction are the plant BMS and the plant vendor's, not Keedian's.
Availability is conditional: without both plant power metering and chilled-water flow the tons cannot be computed, so the metric is simply not offered on that plant rather than estimated from partial data.
| Range | Classification | Interpretation |
|---|---|---|
| At or near the plant's design kW/ton | Expected | The plant is converting power to cooling as designed for the current load and wet-bulb conditions — no action. |
| 5 – 15% above the design figure (sustained) | Efficiency drift — monitor | The plant is working harder than designed for the same output; candidate causes are condenser-tube fouling, low chilled- or condenser-water flow, or poor staging for the load. |
| Greater than 15% above design (no load or weather explanation) | Investigate with the plant vendor | A material efficiency loss with no load or wet-bulb explanation; scope a plant inspection before the excess energy compounds over the cooling season. |
Reference behavior only, expressed relative to each plant's own design kW/ton — not fixed absolute values. A full-plant figure (chillers plus pumps and tower fans) is inherently higher than a chiller-only figure, and both move with load and wet-bulb temperature, so calibrate against the plant's design curve and metering boundary before activating any drift alert.
There is no universal kW/ton target — a water-cooled plant's efficient operating figure depends on its chillers, its metering boundary, the load, and the wet-bulb temperature. The target is the plant's own design / commissioning figure; the metric reports drift against that baseline rather than against a portfolio percentage.
The table below shows how moving Plant Efficiency (kW/ton) impacts each customer value driver the product is designed to improve — the metric page explains the mechanism; the product pages express the magnitude.
| Value driver | Impact strength | How Plant Efficiency (kW/ton) moves this lever |
|---|---|---|
| Energy savings | Direct, primary | On a chilled-water building the plant is the largest single cooling load, so kW/ton is the most direct read on where its energy goes. Catching efficiency drift early — a fouling trend, a flow problem, a poor staging pattern — turns a whole season of quietly elevated plant energy into a scoped inspection. The savings magnitude is expected (pending validation); offices have no named Keedian reference deployment, so it is quantified per plant against its own design, not an invented benchmark. |
The table below summarizes the alarms that fire directly from Plant Efficiency (kW/ton). Each row links to the full operational detail (trigger, preconditions, action plan, human role, escalation, prevention) in the SOPs catalog.
| Alarm | Description | Severity | Tier | AI executes? | Value drivers | SOP |
|---|---|---|---|---|---|---|
| Plant efficiency drift (kW/ton above design) | The plant's metered kW/ton has drifted above its own design / commissioned figure by a set margin, sustained and with no load or wet-bulb explanation — the plant is drawing more power per ton of cooling than it should. A monitoring alarm, not a safety fault: it is communicated at cadence, not dispatched out of cycle. | Medium | Essential | Hybrid | Energy savings | Open SOP → |
More alarms in development (single-metric): a load-normalized efficiency-drift trend that separates degradation from load and weather, and a fouling-trend alert that pairs kW/ton with a declining condenser-side ΔT. Composite plant alarms combining efficiency, Cooling ΔT, and operational compliance to attribute the drift to a specific cause will appear in a future release.
The action plan for each alarm lives on its own SOP page in the SOPs catalog — with the diagnostic steps, human role, value drivers, escalation, and prevention specific to that alarm. The list below maps each alarm to its SOP.
Plant efficiency is reported and alarmed on; Keedian does not stage the plant, reset water temperatures, or otherwise command the equipment. When kW/ton drifts, Keedian surfaces the drift with its load and wet-bulb context and a candidate cause, and refers it to the customer's plant-service vendor. Any staging, reset, or mechanical correction is made on the plant side.
The metric depends on plant power metering and chilled-water flow, and on a fixed meter boundary (chiller-only vs full plant). Confirm both are present and record the boundary and the design kW/ton before activating the metric for a plant. Where the flow or power point is missing, the metric is not offered rather than estimated — an estimated kW/ton would produce false drift.
kW/ton rises legitimately at high load and high wet-bulb temperature. Before reporting a plant as degraded, normalize for load and weather over the period; where several plants in a region move together with the weather, present it as expected context in the MBR rather than a finding, and refer only the genuinely plant-specific drift.
Per-alarm escalation criteria live in the Escalation block of each SOP in the SOPs catalog. The patterns below are metric-level — read from the portfolio view, not from any single alarm firing.