How many kW of power does a 5,000-pallet cold store need, and what is the annual electricity bill?

The question "how many kW does a cold store need for a given number of pallets" is usually answered with a rule-of-thumb coefficient. That coefficient is useful for estimating, but it hides what the project owner most needs to know: which part of the cooling load can be reduced through design and operation. This article recalculates for a specific warehouse, separating each heat source, and then converts the result into an electricity cost under the current EVN tariff.

Example inputs

A freezer store at −18 °C with 5,000 pallet positions, selective racking and a 12 m clear height, receiving 150 pallets per day at a product temperature of −12 °C on arrival, with compressors running 60% of the time on average. Assumptions: design outdoor temperature 35 °C, compressor coefficient of performance (COP) 1.6, plus a 30% allowance for ancillary loads (evaporator fans, defrost, lighting, people, forklifts) and a 10% safety margin. Electricity tariff for the manufacturing group, voltage level from 22 kV to below 110 kV, under Decision 1279/QĐ-BCT; time-of-use periods under Decision 963/QĐ-BCT.

Area: about 1,330 m² of cold room

With a 12 m clear height, the racking fits 6 pallet levels, so 5,000 positions need about 833 ground slots, equivalent to 1,333 m² of cold room. Adding about 15% for buffer rooms and the temperature-controlled picking area, the total air-conditioned area is about 1,530 m². With mobile racking, the cold room area drops significantly, in exchange for slower picking.

Cooling load by source: air infiltration is the big variable

Heat transfer through the panel envelope and floor is about 37 kW. Cooling 150 pallets from −12 °C to −18 °C within 24 hours takes about 15 kW. These two components are almost fixed once the envelope and capacity are chosen. The component that varies strongly is the warm, humid air entering each time a door opens: about 26 kW with a buffer room and air curtain, 52 kW at a moderate level, and 104 kW if doors stay open continuously. After adding ancillary loads and the safety margin, the total cooling load is about 111, 149 and 223 kW of refrigeration respectively.

Compressor power: 70 to 140 kW

Dividing by the compressor COP at −18 °C, the corresponding electrical power is about 70 kW, 93 kW and 139 kW. At 60% running time, annual electricity consumption is about 366,000 kWh, 488,000 kWh and 733,000 kWh. For the same warehouse and the same number of pallets, differing only in how doors and vehicle flows are organized, electricity use can differ by a factor of two.

Electricity cost: VND 0.7 to 1.4 billion a year

Running evenly through the day, with an average price of about 1,952 VND/kWh across the three time-of-use periods, annual electricity costs are about VND 714 million, 953 million and 1.43 billion respectively. Two further operating decisions have a large impact: if the store pre-cools and reduces compressor running during the 17:30–22:30 peak period, the average price in the medium scenario falls to about 1,557 VND/kWh and the electricity cost to about VND 761 million (a 20% reduction). Conversely, if the warehouse buys electricity at the commercial tariff instead of the manufacturing tariff, the same consumption costs about VND 1.44 billion (an increase of about 51%). Identifying the correct electricity customer category therefore needs to be done at the project preparation stage.

How does a chilled store differ from a freezer store?

For a 0–4 °C chilled store of the same size, the panels are thinner and the compressors more efficient, but goods usually arrive at ambient temperature. Cooling 150 pallets of produce from 25 °C to 2 °C each day takes about 115 kW of refrigeration, three times the heat transfer through the envelope. In a chilled store, the main issue is pre-cooling incoming goods and limiting the number of pallets received per day for each room, not panel thickness.

What to settle before choosing equipment

Four parameters determine most of the capacity and electricity cost: product temperature on arrival, pallets received per day, door arrangement (buffer room, fast doors, air curtain, number of openings) and the electricity tariff group. The figures in this article are preliminary estimates for comparing options; an actual refrigeration system design must take into account climate conditions, product characteristics and the specific equipment. Readers can enter their own warehouse parameters into the cold storage calculator to see the results, plan and section.

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