While the electric load is based on the wattage or maximum power draw of each appliance in the house, it also takes into consideration the average amount of time each appliance is used for in a day. Electric load is calculated in watt-hours or kilowatt-hours, which describe the power consumption over the course of an hour. Understanding your house’s electric load helps you identify and control large areas of power consumption. It also points to any modifications that may be required by your electrical system.
Know what you want to calculate. This can seem difficult but it’s really not too hard once you learn the terms. Most electrical appliances are rated with watts, while some use amps. To convert amps to watts, multiply the number of amps by 120. You do this because U.S. home electric outlets use 120 volts, and volts multiplied by amps equal watts. The number you want to find is how many kilowatt hours (kWh) you are using. That is what you meter reads and what you are ultimately billed for.
Create a log of what electrical appliances you use and how long you use them at a time. Keep in mind things that you do not actively (or regularly) control like heating or cooling units, water heaters, freezers, and refrigerators. Make a list for 5 straight days of all the appliances you used, to find a good average on each.
Check the labels on your electrical appliances. This is a start to calculate your electric load and is a good way to get an idea of how much power each appliance uses. One thing to remember is that the number on the label is the maximum watts that appliance will use in an hour, so a refrigerator for instance will only use a small amount of power unless the compressor is running at which time it will use closer to the maximum power.
Estimate the amount of watts you use per appliance a day. If you need help for appliances like heating and cooling units, water heaters or other passive appliances, you can find many estimations on the Interwebs.
Calculate the kWh use for each appliance. The formula for kWh is watts multiplied by hours used and then divided by 1000. For instance, a 100-watt light bulb used for 10 hours would use one kWh.
Add all of the kWh totals from your appliances to get an idea of your electric load that you use every day.
If you want to be incredibly specific you can use a watt-meter to get a better idea of how much electricity individual appliances use. A watt-meter will connect between your appliance’s plug and the wall outlet and it will tell you how much electricity the appliance uses over time.
I would also advise that if you want to convert your findings into actual overhead expense you need to either refer to your electrical provider’s monthly statement of phone them to find out the actual charge for kWh. The rate can vary greatly from zip code to zip code. Your bill might have multiple kWh rates (one for “delivery” and one for “fuel”), and in that case you should to add up them all up to get the total kWh rate. Most rates are tiered, meaning the higher your use, the higher the rate. When we did this for The Bungalow we entered our highest tier into the calculator (yes, we have a tiered system), because I realized the energy we could save would also save us money at the highest tiered rate.
Did You Know?
…an electric clothes dryer uses on average 4400 watts?
…a refrigerator can use upwards of 700 watts?
…a dishwasher can use 3600 watts?…a refrigerator can use upwards of 700 watts?
…a laptop computer uses 40 watts when plugged in?
…a 42″ LCD television uses nearly 236 watts?
…a coffee maker uses 900 peak watts?
I bring all this information to our attention as we here at the r(E)volution continue building and refining our solar power needs. We are looking at a grid-solar combination system but it will help us greatly if we choose appliances and light fixtures and the like with total wattage in mind.