Understand the distinction
Efficiency concerns useful output in relation to input. Total use also depends on the task and how often it happens. Comparing only an efficiency label can miss a change in household size, operating time or the service being delivered.
Put it in your home notes
Write down the intended service before comparing two options. Note operating conditions and use patterns separately from the efficiency claim. A good comparison explains those assumptions; it does not turn an efficient product into a promise of lower consumption under every pattern of use.