The Bureau of Energy Efficiency runs a star-labelling programme for a range of appliances, including chest deep freezers. A label shows a star rating and an energy consumption figure. More stars mean the model uses less electricity than lower-rated models of comparable size in that category.
Star thresholds are revised from time to time as technology improves, so a rating should be read together with the energy figure and the period it applies to. Comparing the actual consumption numbers between two labelled models is more precise than comparing stars alone.
Not every type of commercial refrigeration falls under the labelling programme, so many reach-ins, undercounters and display cases may not carry a BEE label. In those cases, ask for the energy consumption figure and the test conditions behind it. Where a label is present, it is a useful independent check on the manufacturer's efficiency claims.