A greenhouse can use the same monthly kilowatt-hours and receive a higher electricity bill if more equipment operates together during the utility’s demand measurement period. Energy charges pay for consumption in kWh. Demand charges, where the applicable tariff includes them, charge for a measured or otherwise defined level of power in kW. The tariff determines the interval, billing rules and price.
For a grower comparing lighting, pumps and climate equipment, this means an annual kWh estimate is only part of the electricity budget. The operating timetable matters too.
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Read the demand line before changing the controls
BC Hydro provides a concrete example: its explanation describes demand measurements using 15-minute intervals, with the highest average in the billing period used to calculate the demand charge. That is a utility-specific example, not a universal interval for greenhouse projects. BC Hydro: Understand your demand
Obtain the current tariff for the actual connection and confirm these items with the utility:
- The customer class and whether demand charges apply.
- How measured demand becomes billed demand, including any minimum or reference to an earlier peak.
- The measurement interval and any time-of-use periods.
- Other bill components, including fixed charges, taxes and any power-factor charges.
BC Hydro’s rate-design explanation distinguishes basic, energy, demand and power-factor charges. Those categories illustrate why dividing the whole bill by kWh can obscure the cause of a change. They do not establish the charges or rates at another site. Understanding rate design
Two operating schedules, one energy total
Consider this hypothetical example. Both schedules consume 30,000 kWh during a month. Assume an energy price of $0.12/kWh and a demand price of $15/kW for that month. These are invented inputs for arithmetic, not a current utility tariff. For simplicity, billed demand equals that month’s measured peak, with no minimum, historical adjustment, time-of-use rate, tax or fixed charge.
| Item | Schedule A | Schedule B |
|---|---|---|
| Monthly consumption | 30,000 kWh | 30,000 kWh |
| Billed peak demand | 180 kW | 120 kW |
| Energy charge | $3,600 | $3,600 |
| Demand charge | $2,700 | $1,800 |
| Subtotal for these two charges | $6,300 | $5,400 |
The difference is $900 for the month. It exists because the assumed billed peak is 60 kW lower. The example does not claim that a particular greenhouse can achieve that reduction, or that moving equipment operation will preserve the crop environment.
As a smaller illustration, two 20 kW loads running together for one hour consume 40 kWh. Running them sequentially for one hour each also consumes 40 kWh. The combined load is lower during the sequential schedule, but the effect on billed demand depends on the rest of the site’s loads and the tariff’s measurement method.
Find the event that created the peak
Download interval data for the billing period and locate the highest intervals. Compare their timestamps with climate-controller logs and the actual work schedule. A peak may coincide with lighting, cooling, water pumping, packing or several functions operating at once. A meter covering a packhouse as well as the greenhouse will include both.
Then ask a narrow operational question: which work can move without compromising the crop, workers or equipment? A flexible charging task may be easier to reschedule than irrigation during a high-demand period. Cooling required to hold an agreed crop limit cannot simply be postponed to improve the bill.
Do not confuse a brief motor-starting current with a billing-period average. Starting current matters for electrical design and voltage stability, while the tariff determines how demand is measured for billing. The electrical load planning guide addresses the service and equipment side of that distinction.
Check the savings against a full season
Ask the controls or energy specialist to test a proposed operating sequence against measured intervals. A change that lowers one summer peak may do little for winter lighting demand. If the tariff retains an earlier peak in its billing calculation, a lower measured peak may not immediately create the expected saving.
For a new facility, model plausible operating schedules and have the utility confirm the applicable rate before comparing annual bills. Nameplate kW alone does not supply either the monthly energy total or the billed peak.
Record the production limits alongside any demand target. After a change, compare the utility bill and interval data with temperature, irrigation and work records. A lower electricity charge is useful only when the operating schedule still performs the job the greenhouse needs.
