What a refrigerator costs to run
Across 4,704 certified models ENERGY STAR currently lists in this category, the median uses 345 kWh/yr. The cheapest certified model to run costs about $8/year; the most expensive costs about $151/year, more than 19x the spread.
Efficient models versus the rest
Of the 4,704 certified refrigerators tracked here, 2,460 use meaningfully less energy than the category average and 1,719 use meaningfully more, the rest are within about 8% of it either way. The most efficient certified model found is the Fisher & Paykel RS2435V2* at 42 kWh/yr; the least efficient is the Jenn-Air JS48PPDUDE** at 805 kWh/yr.
Your state changes this more than you'd think
The figures above use the simple average of all 51 published state electricity rates (18.8¢/kWh). A median-efficiency refrigerator costs about $42/year to run in North Dakota (12.19¢/kWh, the cheapest state rate this site tracks) and about $159/year in Hawaii (45.95¢/kWh, the most expensive), the identical appliance. Every model page on this site lets you pick your own state to see the real number. See the guide to why location matters this much.
Over its lifetime
NAHB's Study of Life Expectancy of Home Components puts a typical refrigerator's service life at 13 years. At that span, a median-efficiency model costs about $843 in electricity over its lifetime; the least efficient certified model costs about $1,967, a $1,124 gap from the choice of model alone. See the guide to when replacing one actually pays off.
Shopping for a new one
Comparing your current refrigerator's age and running cost against a current certified model is the whole decision this category boils down to.
Compare current ENERGY STAR certified refrigerators before buying.