Refrigerated container electricity costs: measure, calculate and compare

Electrical power, energy and cooling capacity are different

Electrical power in kilowatts (kW) is the rate at which equipment uses electricity. Energy in kilowatt-hours (kWh) is the amount used over time. An average electrical demand of 2 kW over 3 hours represents 6 kWh; a brief 2 kW reading does not establish that the equipment averaged 2 kW for the whole period.

Cooling capacity may also be stated in kW, but it describes heat removal rather than electricity drawn from the supply. A cooling-capacity figure cannot be entered as electrical consumption. Similarly, a maximum connection rating or a starting current is not the unit’s average running demand.

Collect a representative measurement

Ask the supplier which controller logs or metering options are available. If readings come from a separate meter, confirm its units and which equipment it measures. Use the difference between the start and end readings, not the final cumulative number alone. Have suitable metering installed or checked by a competent person where required; this is not a reason to open electrical equipment yourself.

Record the observation’s duration in hours and the circumstances: model, setpoint, ambient conditions, stored goods and their arrival temperature, door-opening routine and any unusual event. Include normal operating cycles. A short observation during initial cooling can differ from steady storage, while a quiet empty period can understate a busy loading day.

Keep the scope consistent. If one meter supplies three containers, its reading is already for that group. Either project the same group’s consumption or obtain a justified allocation; multiplying the group reading by three again would overcount. Do not subtract other equipment’s use unless you can support that adjustment.

• Equipment model and the exact container or group measured.
• Meter units, start reading, end reading and elapsed hours.
• Required temperature and representative ambient conditions.
• Stock loading, door use, initial cooling and defrost or unusual events.
• The evidence date and whether future operation is expected to match it.

Choose measured data or an explicit assumption

With a measurement, the calculator divides observed kWh by observation hours, then multiplies that average by your projected days and powered hours per day. The measurement remains historical evidence; the forward total is still a projection that assumes comparable operation.

If you have no measurement, select the assumption method and enter an average electrical kW value you can explain. It might come from a supplier’s documented test under stated conditions or your own labelled planning scenario. Do not copy the cooling capacity or maximum rated input into this field and call the result normal consumption.

Powered hours describe the period represented by the average, not just the minutes when a compressor is audibly running. If the average already includes cycling and standby, applying a further duty-cycle discount would count the same adjustment twice. The calculator does not recommend switching refrigeration off; the operating schedule must meet the needs of your stock.

Worked example: a hypothetical 14-day project

These figures are invented to demonstrate arithmetic, not market tariffs or expected consumption. Suppose a clearly identified unit uses 240 kWh over a representative 72-hour observation. You want to project 14 days at 24 powered hours per day, using an assumed tariff of £0.2375/kWh and £14 of other supply charges for that project.

The observed average is 240 ÷ 72 kW. The projection is 240 ÷ 72 × 14 × 24 = 1,120 kWh. At the assumed tariff, the energy charge is £266. Adding the £14 supply charge gives £280 on the entered tax basis. If both inputs exclude VAT and the hypothetical confirmed rate is 20%, the total becomes £336 including VAT.

Changing only the assumed unit price to £0.30/kWh gives £336 for energy, £350 with the same other charges, and £420 with that same hypothetical VAT rate. Consumption has not changed. This separates tariff sensitivity from equipment performance. Use your actual bill and applicable rate for a real project.

Read the tariff and keep the cost boundaries clear

The unit-price input uses pounds per kWh: enter 0.25 for 25p. It accepts four decimal places so a quoted fractional-penny rate can be represented. Use the same tax basis for the unit price and the other charges. If different tax treatments apply, obtain appropriate inclusive figures before using one combined calculation.

If prices vary by time of day, calculate each consumption band using its own measured kWh and price, or obtain a supported weighted average. A simple unweighted average of two rates is only appropriate when the consumption weights justify it. The single-rate calculator cannot reconstruct tariff bands from one total meter reading.

Add only supply charges attributable to the project that are not already in the unit price. A pre-existing site standing charge may not be an extra consequence of renting a container; keep your allocation explicit. Delivery, hire, installation, monitoring, service and collection belong in the wider project budget, not silently inside the electricity figure.

Prepare the complete refrigerated-container brief →Build the equipment hire budget →

Compare equipment on the same operating duty

Ask each supplier for the model, the test or observation conditions and what was included in any energy figure. Match the required temperature, stock conditions, usable capacity, access routine and ambient conditions. A more efficient result from a different test is not automatically a saving at your site.

Age and container length alone do not settle the comparison. Condition, controls, insulation, seals, loading and maintenance can affect operation. Ask how the supplier will investigate an unexpected increase and what service response is included. A pre-delivery test does not guarantee one electricity bill for every use.

For an operational improvement, keep the stock’s required conditions unchanged and compare suitable measurements before and after. Door routines, airflow and maintenance deserve attention, but there is no universal percentage saving to apply. Do not change product temperature requirements simply to make a calculator result smaller.

Confirm the connection and the response to a power failure

An electricity-cost estimate does not approve the supply. Give the actual unit specification to the supplier and a competent electrician, including the intended location and cable route. Confirm the connection, protection, isolation and commissioning responsibilities before delivery; a generic socket rating cannot answer all of those questions.

Average kW also cannot size a generator by itself. Starting behaviour, other connected loads and the equipment’s electrical requirements need a separate assessment. If backup operation matters, agree a suitable plan and its costs instead of assuming a portable generator can be connected when a problem occurs.

Agree who receives alarms, who acts outside normal hours and where stock can go if the unit cannot maintain conditions. Keep response-time commitments distinct from a telephone line described as available 24/7. Ask about monitoring, call-outs, exclusions and any stock-loss arrangements in the contract.

Turn the result into a supplier question

Save the scenario with its evidence and assumptions. Include the unit or group, operating requirement, observation conditions, projected period and tariff basis. A useful question is whether the supplier can support or improve that scenario for the same duty, not whether it can guarantee a generic low daily electricity price.

The summary can be copied, downloaded or added to an editable quote request. Keep the full meter log and technical specification separately. The tool’s compact summary is a starting brief, not an electrical design, a cold-chain protocol or a supplier quotation.

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