What Size Generator Do I Need to Run a Cold Room or Freezer

Compressors are the problem, not the running power

• A cold room compressor may run at 1-2 kW but draw 3-4 times that current for a few seconds at start.
• If the generator cannot deliver that surge, the compressor stalls and the overload trips the breaker.
• Rule of thumb: generator starting capacity should be at least 3 times the compressor running power.

Recommended sizes

• Chest freezer and fridge in a shop: 5-6 kW.
• Small cold room up to 5 cubic metres: 9-12 kW.
• Cold room with two or three compressors: 15-18 kW, or start compressors one by one.

What to tell us when ordering

• How many compressors, their power in kW or HP, and whether they start at the same time.
• Whether the site is in a residential area (choose silent type) or an industrial yard (open frame is enough).
• Ambient temperature, because high temperature reduces alternator output by about 5-10 percent.

Extra margin for hot climates

• In 40 degrees Celsius ambient, derate the generator by around 10 percent.
• Add one step up in model rather than running a smaller set at full load all day.