If it's an older refrigerator or a dusty house, check the refrigerator coils. In particular if it's set to a pretty cool setting but doesn't seem very cool or is running frequently it may be time for replacement.

You can also get any of a variety of temperature sensors (I like SensorPush) and stick one in the fridge to get a pretty good idea of how much it's running the compressor.

Another thing to look at if there's central forced-air heating/cooling may be whether it's set to have the fan always running. That can be useful in balancing temperatures between floors, but it's still a fan using electricity to move air.