Typical plant efficiencies
The working figures for first-pass estimates, consistent with the worked examples across the courses. Real plant varies with age, load and maintenance; treat these as the starting point an audit then measures against.
Last reviewed July 2026. Figures are indicative working values for first-pass estimates; confirm anything compliance- or design-critical against the cited source.
Heat generation
| Plant | Typical figure | Notes |
|---|---|---|
| Shell (fire-tube) boiler, good order | 80–85% | Falls with fouling and excess air |
| Condensing boiler, actually condensing | 90–92% | Needs return water below ~55 °C |
| Condensing boiler on a hot circuit | ≈ standard boiler | Never reaches dew point |
| Electric resistance heating | 100% (COP 1) | Efficient but expensive per kWh of heat |
| Air-source heat pump (space heating) | SCOP ≈ 2.8–3.5 | Depends heavily on flow temperature |
| Ground-source heat pump | SCOP ≈ 3.5–4.5 | Steadier source, smaller lift |
| CHP (gas engine), overall | 80–90% | Only with the heat genuinely used |
| CHP electrical share | 35–42% | Reciprocating engine |
Cooling
| Plant | Typical figure | Notes |
|---|---|---|
| Air-cooled chiller | COP 2.5–3.5 | Worse on hot days, exactly when loaded |
| Water-cooled chiller (tower) | COP 4–6 | Wet-bulb rejection buys the difference |
| Condensing-temperature rule | ≈ 2–3% per °C | Every degree of lift avoided saves this |
| Heat-recovery ventilation (MVHR) | 70–90% effectiveness | Sensible heat recovered from exhaust air |
Motive power & compressed air
| Plant | Typical figure | Notes |
|---|---|---|
| Electric motor (IE3, full load) | ≈ 93% | See the motor reference page |
| Compressed air, wire to tool | 10–15% | Most input becomes recoverable heat |
| Compressed air specific energy | 0.10–0.13 kWh/m³ | At 7 bar g; trend it monthly |
| Compressor heat recoverable | 70–90% of input | As warm air or hot water |
| Pressure rule of thumb | ≈ 7% per bar | Generation energy per bar of setpoint |
Lighting
| Source | Efficacy (lm/W) | Notes |
|---|---|---|
| Incandescent | 10–15 | Phased out |
| Halogen | 15–25 | Phased out for general lighting |
| Compact fluorescent | 50–70 | Legacy |
| Linear fluorescent (T5) | 90–100 | Plus ballast losses |
| LED | 100–180 | The default; quality varies |