Start with the Australian Energy Rating Label, comparing the star rating and estimated annual energy use with similar-sized models. A higher star rating can indicate better efficiency, but the kilowatt-hours per year figure is often more useful for estimating running costs. Multiply that figure by your electricity usage rate to get an approximate annual cost, remembering that actual costs depend on how you use the appliance and your energy plan. Check the official Energy Rating website or ask the retailer for current product details before buying.