I have a builder-grade 12 year old 24 cu.ft. Freezer up top refrigerator. I've been looking at the power consumption of various things in our house with a new Belkin real-time wattage meter. I plugged it into our refrigerator. When the compressor is off, it reads zero. When you open the door, it reads 42 watts... the light bulb. When the compressor is running, it reads 156 watts. Open the door and it reads 208 watts... compressor plus light bulb. I walked past just now and it read 480 watts! I opened the door and it jumped to 520... whatever plus light bulb. I did not hear the compressor. It stayed that way for about 10 minutes. Then the compressor came on and it read 156 again.

What would cause the refrigerator to pull that much electricity?

The higher reading could be the load of the electric defrost heater.

30 ohms resistance on defrost heater = 4 amps 4 amps x 120 volts = 480 watts

It's the defrost heater. They are rated at 450-500 watts. Yours is working perfectly.