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

Updated: April 1, 2016

Woman looking in a fridge
An older spare refrigerator could be costing you as much as $90 a year to operate.

Want to cut your home energy use? First, understand how you're charged

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

To figure out how much it costs to run each electrical device in your home, from appliances to heaters to hair dryers, we turned to BC Hydro's Pat Mathot.

What is a kilowatt-hour?

First, a reminder: 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:

  • How many watts the device draws
  • How much or how often it's used.

To calculate kWh, you take the wattage of the device, multiply that by the number of hours that 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.

Our residential usage charge is a two-tiered Conservation Rate. You pay 8.29 cents per kWh for the first 1,350 kWh you use over an average two-month billing period. Above that amount, you pay 12.43 cents per kWh — what we call Step 2 — 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.

So if you're trying to avoid hitting that Step 2 rate, keep an eye on the biggest electricity draws in your home to help reduce your usage.

Heating is the big one

For the average B.C. household, about 50 per cent of home energy use over the 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 relies on electric heating, you may find yourself paying the Step 2 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 shares a few things to keep an eye on in your quest to avoid that Step 2 rate.

Cost culprits

The heat is on: The No. 1 item that residential customers miss in terms of energy usage is electric heaters that 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 step 1 rate."

However, many homes have a second fridge and/or freezer — so if you do, 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 per cent 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: Most homes still use considerable energy while you're asleep, including 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 per cent 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."


Household devices: Annual costs

While your experience with devices below may vary, here's a look at the approximate annual costs of operating various devices and appliances, using the lower Step 1 rate of 8.29 cents per kilowatt hour:

  • Clothes dryer (6,200W, 8 cycles/week): $78
  • Toaster (1,100W toaster, 5 minutes/day): $3.19
  • Coffee maker (1,500W, brewing 10 minutes/day, warming 1 hour/day): $9.62
  • Old refrigerator (380W, 24 hours/day): $118
  • 15 incandescent light bulbs (600W, 3 hours/day): $68
  • TV 42" LCD (132W, 5 hours/day): $20
  • Clothes washer (700W, 35 loads/month): $32
  • Computer & 17" LCD Monitor (24 hours/day, no power management): $73
  • Dishwasher (1,200W, using heat dry cycle 20 hour/month): $30

Cooling & Heating: Monthly costs

Because heating and cooling costs tend to be seasonal, the numbers below reflect monthly costs for operating these devices.

Your costs may be different, depending on the device, how much you use it and whether you use it during periods when your consumption has taken you into the higher Step 2 rate. Numbers below reflect Step 1 rate costs.

  • Floor fan (75W, 10 hours/day): $1.60
  • Window unit air conditioner (1,00W, 10 hours/day): $13.90
  • Electric space heater (1,400W, 4 hours/day): $13.90