A 5 GH/s Bitcoin Miner is running at around 270 Watt. I tested it with an Wattmeter. Is that a reasonable amount of Watt? In the comparison list on Bitcoin.it it says that those devices are running at 30 Watts! What is wrong with this miner?
If you can hold your hand on the Bitcoin Miner for an extended period of time without burning it, I doubt the cube is consuming 270 Watts. What does your mining software indicate the temperature is? My two cubes run at temperatures between upper 30s and low 50s Celsius. (These cubes do make nice winter hand warmers for cold typing hands:-)
Once you rule out the cube is not sucking the power, the question then becomes what about the associated power brick or the integrity of the meter. Again, imagine the heat a sixty Watt indecent light bulb puts out. If your brick can't be held for an extended period of time without burning your hand, you got a bad brick that mightbe a fire hazard. Otherwise, you got a bad meter or your house may need capacitive power factor (PF) correction where you plug your cube into an outlet.