Introduction

 Fig. 1: Switchable Power Strip. (Source: Wikimedia Commons)

Devices and appliances consistently use energy in our homes when plugged into outlets. Even when they're turned off or on standby, small amounts of current run through the circuits and the electrical energy is converted into wasted heat. This is the concept of Phantom loads; devices, seemingly turned off, using up power and ringing up the power bill. Almost all of us can see something similar to Fig.1 in our homes and offices, unaware of how much energy just 'disappears'. But how significant is this energy sink?

Analysis of the Energy Wasted

To understand the amount of energy wasted, I'll be estimating the amount of energy my desktop computer at home consumes while it is in low-power (sleep) mode. I will estimate the energy use of the CPU and two LCD monitors. A desktop CPU consumes 9W of power on average and an LCD Monitor consumes an average of 2W of power on average. [1]

 E = (9 + 2 + 2) W1000 W/kW × 22 hours1 day × 365 days1 year = 104.4 kWh/year

Estimating that I use the computer for ~2 hours per day and it is in sleep mode the rest of the time, we calculate 104.4 kWh of energy wasted by the computer per year. This is equivalent to the energy required to drive 372.8 miles on a freeway (with an efficiency of 0.28 kWh/mi). [2] Given an average of 12 cents paid per kW of electricity, we calculate an approximate of \$12.53 per year for energy from which I derive no use. [3]

While this may seem a small amount for me personally, it will result in a significant amount of energy being wasted when summed up to include all the computers in all households across the country.