The kilowatt-hour defined, and what it means to you

Wake up to the cost of electricity. While a toaster needs a lot of power, it won't cost you much over a year if you use it for only a few minutes a day. Heating, on the other hand, accounts for half the energy costs of the average B.C. home.

Want to cut your home energy use? Start by understanding how you're charged

By definition, a kilowatt-hour is easily understood. But it can be hard to make dollars and sense of what it really means for daily home consumption.

So for those wishing to plug-in to the kWh costs of everything pulling power in your home, BC Hydro Power Smart's Pat Mathot takes you on a tour of an average home.

What is a kilowatt-hour?

When you take a cab, you are charged by the kilometre. However, that doesn't tell you what matters most: for instance, how much it costs to get to your hotel from the airport.

For electric utilities, the kilowatt-hour (kWh) is the most common billing unit for energy delivered to consumers. A kilowatt-hour is a unit of energy equivalent to one kilowatt of power expended for one hour of time.

There are two simple elements to understanding your kilowatt-hour consumption:

  1. How many watts the device draws
  2. How often it's used.

"A toaster is a relatively big power draw at 1,000 to 1,500 watts, but if you only run it three minutes a day, it's only going to cost you $1.25 over the year," says Mathot, residential marketing manager for BC Hydro Power Smart.

To calculate kWh, you take the wattage of the device, multiply that by the number of hours you predict it's used, and divide by 1,000. For example, says Mathot, if you use a 100-watt incandescent bulb for 10 hours, then you have consumed 1 kWh of electricity.

BC Hydro's residential usage charge is a two-tiered rate. You pay 6.80 cents per kWh for the first 1,350 kWh you use over an average two-month billing period. Above that amount, you pay 10.19 cents per kWh — what we call the Conservation Rate — for the balance of the electricity used during the billing period.

This structure is designed to encourage conservation, with what's known as the Step 2 rate significantly higher than the Step 1 rate.

Back to that light bulb. Used 10 hours at the Step 1 rate, it would cost you 6.8 cents for those 10 hours. At the Step 2 rate, it would cost about 10.2 cents.

An easy way to save? Swap that 100-watt incandescent for an equivalent 23-watt compact fluorescent (CFL) and costs would be 1.5 cents at Step 1, 2.5 cents at Step 2.

Heating is the big one

thermostatHomes are like snowflakes: no two are exactly the same. But for the average B.C. household, about 50% of home energy use over the course of a year is for space heating, usually generated by electricity, gas or a combination of both.

"The potential big ticket items in most homes will be anything that heats and cools air space or water," says Mathot. "Big energy consumers in a home can be multiple fridges or freezers, heaters, air conditioners, heavy use of dryers and, if applicable, electric hot-water heaters."

If you have a larger home, particularly one that uses a lot of electric heating, you may find yourself paying BC Hydro's Step 2 Conservation Rate regularly in the winter months. But if you have a smaller or very efficient home, you may be avoiding the higher rate all or most of the time.

Below, Mathot looks at a few things you can keep an eye on in your quest to avoid that Conservation Rate. And we also feature a list of monthly costs for some sample devices and tasks.

Cost culprits

The heat is on: The No. 1 item that residential customers miss in terms of energy usage is electric heaters they didn't know were on.

"Electric heaters can be big draws of up to 1,500 watts each. And if it's on, constantly cycling, that one heater can cost you $150 over a two-month billing period," says Mathot.

Watts cooking?: Your kitchen can be a big eater of energy. A typical 19 cubic foot non-ENERGY STAR top-freezer refrigerator runs at 80 watts, while an average stovetop operates at 1,600 watts while in cook mode. "One fridge is probably 500 to 700 kWh per year and a range is approximately 700-1000 kWh per year, depending how much cooking you do. Combined, that works out to $116 using the low-end charge rate."

However, many homes have a second fridge and/or freezer — so double-up on that cost.

High-def a high draw: The biggest single area of growth in electricity consumption right now is electronics, says Mathot. He estimates his home's one entertainment centre takes up a combined 1,000 kilowatt-hours per year (basic usage charge: $68); almost 20% of his home's consumption.

"My television is 400 watts when it's on. And when I have my TV, PVR and PlayStation all operating, it's pushing 500 watts. Combined, that's more than my fridge draws."

On standby: While you are fast asleep at night, your house remains restless. Without even taking into consideration lights left on, nocturnal life in a home includes running fridges and freezers, time-ticking clocks, cell-phone or battery chargers, and entertainment devices constantly searching for signals.

"There are some statistics that estimate 10% or more of your bill can be attributed to standby mode on assorted devices. On standby, my TV is approximately five watts, but that's running all hours at a cost of $3 per year — and that's just one, lone electronic device."

Most electronics operate at two to five watts in standby mode. Learn more about standby electricity use.