How do we estimate a motor's electricity use from its horsepower rating?
Convert horsepower to kilowatts (1 hp is 0.746 kW), multiply by how loaded the motor runs, divide by its efficiency, then multiply by running hours. It is an estimate; a meter or the electricity bill beats it. Use it to split a bill between machines, not to replace the bill.
Inputs
- Nameplate rating in hp or kW (this is output power).
- Typical load as a share of rating.
- Efficiency from the nameplate.
- Running hours from a log.
When to use it
To allocate a known bill across machines or to size a saving. Your reported Scope 2 still comes from the bill.
Worked example (illustrative)
- 15 hp × 0.746 = 11.19 kW output
- At 75% load and 90% efficiency: 11.19 × 0.75 ÷ 0.90 = 9.33 kW input
- 3,000 hours: about 27,975 kWh × 0.710 = 19.9 t CO2
What Senseible does here
Senseible reads electricity bills (CEA grid factor 0.710 kg CO2 per kWh, CO2 Baseline Database version 21.0) and diesel, LPG and gas invoices (IPCC 2006 defaults) into a dated, fingerprinted Scope 1 and 2 record for each site, and labels estimates as estimates.
Sources: CEA CO2 Baseline Database, version 21.0, GHG Protocol Scope 2 Guidance
Last reviewed 2026-10-23.