9. The Little Things: How Big Are They?
The Little Things: How Big Are They? Most of us these days are concerned about how we use energy. We tend to be aware of a light left on or a cell phone charger left plugged in. So we turn the light off or unplug the charger and tell ourselves we have made a difference. If you have been following our columns you may well guess the next question: HOW MUCH DIFFERENCE? Compared to what? Let's start with some basics on electricity usage. When you buy electricity, it comes in units of kilowatt-hours (kWh). Your electric appliance or device uses energy at a rate determined by its wattage (e.g. a 100 W light bulb). So, wattage is the RATE at which it uses energy. To get the AMOUNT of energy it uses (kWh), divide the wattage by 1000 and multiply it by the hours it is used. If a 100-watt incandescent bulb is left on for 5 hours it uses 100W/1000, or 0.100 kW. Multiplied by 5 hours this comes to the amount of 0.5 kWh. It will cost you ab...