Start with the laundry you actually do
Think about your usual loads and the largest item you wash regularly. Compare washers with enough drum capacity for those loads. Check the dimensions and installation instructions for each model. Make sure there is room for the door or lid to open fully and for the clearances the manufacturer calls for.
Put two yellow labels side by side
Find the EnergyGuide label for the exact model on the appliance or on the seller's or manufacturer's site. Compare similar models and look for estimated annual electricity use, usually shown in kilowatt-hours per year, or kWh per year. Compare costs using the same water heater type. The FTC explains that the label estimates use typical usage and a national average energy price.
Put the price difference beside the energy estimate
Suppose two washers cost $600 and $720 in total. Both totals include delivery and installation. On the same label basis, their annual energy cost estimates are $35 and $15. The $120 price difference divided by the $20 yearly difference gives six years using those estimates. Your use and rates can change the result. Keep differences in water use, repairs and other costs separate from this calculation.
Check water use separately
For ENERGY STAR certified models, look up the exact model in the program's Product Finder. The Integrated Water Factor compares water use in relation to drum capacity. A lower value means greater water efficiency on that measure. Use it alongside the EnergyGuide figures and the delivered price.