For a greenhouse, track the dehumidifier’s electricity separately from heating fuel: power is an instantaneous rate, energy is accumulated use, and a rating is a test result.
Power, energy, and the meter
According to the EIA electricity measurements, power describes the rate at which equipment uses electricity. Watts (W) and kilowatts (kW) measure power; 1,000 W equals 1 kW. Energy is power accumulated over time, measured in watt-hours (Wh) or kilowatt-hours (kWh). A greenhouse ledger should therefore pair each reading with the same time interval. A whole-building kWh total does not identify one machine by itself, although some advanced smart-meter systems can provide device-level tracking.
An eight-hour two-power window
For one device and one meter boundary, assume mutually exclusive, constant-power intervals covering an 8-hour window: 6 h at 0.240 kW and 2 h at 0.040 kW. Energy is 0.240 × 6 + 0.040 × 2 = 1.52 kWh. Both power values are assumptions for this example, not product or standby ratings.
At an illustrative electricity rate of $0.12/kWh, that window costs 1.52 × $0.12 = $0.1824. Thirty identical windows would total 45.6 kWh and $5.472, rounded at the end to about $5.47. These are assumed repeated windows; other hours are outside the calculation and are not treated as zero use.
Measured draw versus a constant-power estimate
For a real estimate, use device power or energy records for the same interval and meter boundary. Operating-time proportions alone cannot establish water removal or efficiency. This bookkeeping approach follows Robert Grisso, Martha Walker, and John Ignosh, Virginia Cooperative Extension, Virginia Tech, and Virginia State University, in the VCE energy-use guide.
Capacity and IEF answer different questions
Residential dehumidifier capacity is a water-removal quantity, commonly expressed as pints per 24 hours under specified ambient conditions. The Integrated Energy Factor (IEF) is a residential efficiency ratio in litres per kilowatt-hour; its test weighting can include dehumidification, standby, and off modes. The ENERGY STAR efficiency criteria define those rating concepts. They are controlled residential indicators, so do not divide a greenhouse’s water load by a residential IEF to forecast site electricity. Equipment capacity and the electricity used by a greenhouse installation require their own operating evidence.
Compare like test conditions
Reported residential capacity can change when the test conditions change. A lower number under another test basis is not, by itself, evidence that the machine deteriorated. Use the same test method when comparing labels, and treat the household test temperature as a test condition rather than a greenhouse setpoint. A capacity label alone also does not establish consumption at your crop, climate, controls, or operating interval. See ENERGY STAR testing and capacity for the residential test explanation.
A bounded greenhouse heat-recovery model
A Wageningen study modelled a non-illuminated tomato crop in a Venlo-type greenhouse under typical Dutch weather. Compared with earlier outside-air-exchange humidity-control cases, its heat-pump circuit’s cold surface cooled air, so heating demand rose. This bounded result does not mean every standalone dehumidifier cools its room. See the Wageningen study.
Keep heating, gas, and electricity in separate lines
In that model, recovered heat served part of the heating demand first, while purchased gas supplied the remainder. The heat pump and fans also used electricity. Consequently, lower gas consumption does not automatically mean lower electricity consumption. For that reporting period, the modeled energy charge is gas quantity × gas price plus electricity quantity × electricity price. Keep the scope explicit: add a component’s electricity only when it is not already included in the reported device or system total. Never count the same fan, heat pump, or dehumidifier electricity twice. This charge is not a forecast of ownership cost, a universal greenhouse result, or a saving guarantee.
