Ontario Electricity Cost and Time of Use Rates: How to Calculate What Appliances Cost to Run

Introduction

If you have opened an Ontario electricity bill and wondered why the total is higher than the energy rate multiplied by the energy you used, you are not alone. The bill has several parts, the price of energy changes by time of day for many households, and appliances draw power at very different rates. A small phone charger and a space heater can both be plugged in for an hour, but their costs are far apart.

This guide from Mississippi Maple explains the math in plain language. It shows how to turn watts into kilowatts and kilowatt hours, how Ontario time of use pricing works, and how to estimate the running cost of almost any appliance in your home. It does not give financial advice. It shows how the calculations work so you can check your own bill, compare habits, and use the calculators linked at the end with better inputs.

All examples use metric units first. Where an appliance nameplate or a common household reference uses imperial units, those appear in parentheses to help you match what you see at home.

How an Ontario electricity bill is built

An Ontario residential bill is not a single charge. It is a group of charges that together pay for generating electricity, moving it to your home, and operating the regulated system that keeps it reliable.

The energy charge

The energy charge is the part most people mean when they talk about the price per kilowatt hour. It is based on how many kilowatt hours you used in the billing period and, if you are on time of use pricing, when you used them.

If you use 800 kilowatt hours in a month and all of that use fell in one price period, the energy charge would be 800 multiplied by the rate for that period. In real life, use is spread across off peak, mid peak, and on peak periods, so the bill applies a different rate to the portion used in each period. Your meter records the timing, and the utility totals each bucket separately.

Delivery and regulatory charges are separate

Delivery charges cover the cost of bringing electricity from the generation system through transmission lines and local distribution lines to your home. They can include a fixed monthly component and a variable component linked to use. Regulatory charges cover system operation and other regulated costs.

This separation matters for appliance math. When this guide calculates the cost to run a space heater, it calculates the energy portion only, using the time of use rate. Your actual bill increase from running that heater will be higher because delivery and regulatory charges also apply to the extra kilowatt hours, and some charges do not scale in a simple straight line. Always read the line items on your own bill to see how your utility structures those parts. The energy calculation is still useful. It lets you compare appliances fairly and see how timing changes the energy portion.

Taxes and rebates

Taxes and any applicable provincial rebate or program adjustment appear as separate lines for many customers. Those lines depend on current rules and on whether the account qualifies. This guide does not estimate them, because they are not part of the watts to kilowatt hours formula and they can change without changing how much power an appliance draws. Check your own bill for how they appear on your account.

Ontario time of use pricing explained

Time of use pricing means the energy rate depends on when you use electricity. The idea is straightforward. Demand is lower overnight and on weekends, higher during busy daytime and early evening hours on weekdays, and the price periods reflect that pattern. The exact clock hours for each period change by season and are set by the regulator, so confirm the current schedule on your bill or with the regulator before you shift a major load based on timing alone.

The rates in this guide and in the Mississippi Maple electricity cost calculator are preset defaults from the calculator. They are editable defaults to check against your own bill or the regulator. They are not a promise that your current rate is the same today, because rates are reviewed and can change.

Calculator preset rates used in this guide

The calculator preset used for the worked examples is:

Off peak: 0.098 dollars per kilowatt hour, as an editable default to check against your own bill or the Ontario Energy Board.

Mid peak: 0.157 dollars per kilowatt hour, as an editable default to check against your own bill or the Ontario Energy Board.

On peak: 0.203 dollars per kilowatt hour, as an editable default to check against your own bill or the Ontario Energy Board.

To see why timing matters, compare the same 100 kilowatt hours in each period using only the energy portion. At the off peak preset, 100 multiplied by 0.098 equals 9.80 dollars. At the mid peak preset, 100 multiplied by 0.157 equals 15.70 dollars. At the on peak preset, 100 multiplied by 0.203 equals 20.30 dollars. The appliance did the same work in each case. Only the timing, and therefore the rate bucket, changed.

Who is not on time of use

Not every Ontario customer pays time of use rates. Some customers are on a tiered plan, where the rate changes after a threshold amount of use in the billing period, and some are on other contracts or plans. If your bill shows tiered pricing instead of off peak, mid peak, and on peak buckets, the watts to kilowatt hours math in this guide still applies. You would simply use the tier rate that applies to that portion of your use instead of a time of use rate.

If you are not sure which plan you are on, look for the labels on the electricity line of your bill. They will say time of use or tiered, and they will show the kilowatt hours charged in each bucket.

The core formula: watts to kilowatts to kilowatt hours

Every appliance cost estimate in this guide uses the same three step formula. Once you learn it, you can estimate a kettle, a dryer, a dehumidifier, a hot tub heater, or a gaming computer with the same method.

Step 1: Find the watts

Watts measure the rate at which an appliance draws power while it is running. Look for a label on the appliance, on its power supply, or in its manual. It may say W for watts, or it may list volts and amps. If it lists volts and amps, multiply volts by amps to get an approximate watts figure. For example, 120 volts multiplied by 10 amps equals 1,200 watts.

Some appliances cycle on and off, such as fridges, furnaces, and hot tubs. Their label watts describe the draw while the motor or heater is active, not a constant draw for every minute of the day. For those, you need to estimate active hours, not just plugged in hours. That is why hot tub and heating estimates ask for hours of active heating or filtering rather than assuming 24 hours at full power.

Step 2: Convert watts to kilowatts

There are 1,000 watts in one kilowatt. Divide watts by 1,000 to get kilowatts.

For example, 1,500 watts divided by 1,000 equals 1.5 kilowatts. A 100 watt bulb is 100 divided by 1,000, which equals 0.1 kilowatts. A 9 watt LED bulb is 9 divided by 1,000, which equals 0.009 kilowatts.

Step 3: Multiply kilowatts by hours to get kilowatt hours

A kilowatt hour is one kilowatt used for one hour. Multiply kilowatts by the number of hours the appliance runs at that power level to get kilowatt hours.

For example, 1.5 kilowatts multiplied by 2 hours equals 3 kilowatt hours. That is the energy used.

Step 4: Multiply kilowatt hours by the rate

Multiply kilowatt hours by the dollars per kilowatt hour rate that applies at that time to get the energy cost.

For example, 3 kilowatt hours multiplied by 0.157 dollars per kilowatt hour, the mid peak preset listed above as an editable default to check against your own bill or the Ontario Energy Board, equals 0.471 dollars, or about 47 cents, for the energy portion of those two hours.

Written as one line, the formula is: cost equals watts divided by 1,000, multiplied by hours, multiplied by rate in dollars per kilowatt hour.

How to estimate any appliance in your home

Start with a short list of the appliances you run most often or the ones with the highest watts. Heating and cooling appliances usually dominate because they draw 1,000 watts or more and run for hours. Lighting used to be a larger share, but LED bulbs use so much less power that a whole room of LEDs can cost less to run than a single older bulb.

For each appliance, write down four numbers: watts, hours per day, days per month you use it, and the price period it usually runs in. Then apply the formula. If an appliance runs across price periods, split it. For example, a dishwasher run in the evening might start in one period and finish in another. For a first estimate, most people assign the whole run to the period when it starts and note that the estimate is approximate.

Portable heaters, block heaters, and pool or hot tub heaters deserve special care because small changes in hours make a large difference. Adding one extra hour per day to a 1,500 watt heater adds 1.5 kilowatt hours per day. Over 30 days, that is 45 extra kilowatt hours before you apply any rate.

For electronics that stay plugged in, check whether the watts figure is for active use, standby, or charging. A laptop might draw far less while you type than its power supply maximum suggests. Using the maximum gives you a ceiling estimate, which is useful for comparison but may overstate daily use. When a calculator lets you edit watts and hours, try both a typical case and a high case to see the range.

Worked example

The two examples below show every step, so you can copy the method for your own appliances. Both use the calculator preset rates already labelled in this guide as editable defaults to check against your own bill or the Ontario Energy Board.

Example 1: A 1,500 watt space heater at mid peak

Question: How much is the energy cost to run a 1,500 watt space heater for 6 hours a day for 30 days, if all of that use is at mid peak?

Step 1: Convert watts to kilowatts. 1,500 divided by 1,000 equals 1.5 kilowatts.

Step 2: Find kilowatt hours per day. 1.5 kilowatts multiplied by 6 hours equals 9 kilowatt hours per day.

Step 3: Find kilowatt hours for the month. 9 kilowatt hours per day multiplied by 30 days equals 270 kilowatt hours.

Step 4: Apply the mid peak preset rate. The mid peak preset is 0.157 dollars per kilowatt hour, an editable default to check against your own bill or the Ontario Energy Board. 270 multiplied by 0.157 equals 42.39 dollars.

Answer: The energy portion is 42.39 dollars for that month of use at that preset rate. Delivery, regulatory charges, and any taxes or adjustments on your bill are separate and would add to the bill total.

For comparison, the same 270 kilowatt hours at the off peak preset of 0.098 dollars per kilowatt hour, an editable default to check against your own bill or the Ontario Energy Board, would be 270 multiplied by 0.098, which equals 26.46 dollars for the energy portion. At the on peak preset of 0.203 dollars per kilowatt hour, an editable default to check against your own bill or the Ontario Energy Board, it would be 270 multiplied by 0.203, which equals 54.81 dollars. The heater used the same energy in each case. Timing changed the energy cost.

Example 2: Swapping ten bulbs from 60 watts to 9 watt LEDs

Question: How much energy do you save in a year by swapping ten 60 watt bulbs for ten 9 watt LED bulbs, if the lights are on for 5 hours a day?

Step 1: Find the old total watts. 10 bulbs multiplied by 60 watts equals 600 watts. 600 divided by 1,000 equals 0.6 kilowatts.

Step 2: Find the old daily energy. 0.6 kilowatts multiplied by 5 hours equals 3 kilowatt hours per day.

Step 3: Find the old yearly energy. 3 kilowatt hours per day multiplied by 365 days equals 1,095 kilowatt hours per year.

Step 4: Find the new total watts. 10 bulbs multiplied by 9 watts equals 90 watts. 90 divided by 1,000 equals 0.09 kilowatts.

Step 5: Find the new daily energy. 0.09 kilowatts multiplied by 5 hours equals 0.45 kilowatt hours per day.

Step 6: Find the new yearly energy. 0.45 kilowatt hours per day multiplied by 365 days equals 164.25 kilowatt hours per year.

Step 7: Find the yearly saving in energy. 1,095 minus 164.25 equals 930.75 kilowatt hours saved per year.

Step 8: Turn the energy saving into a dollar illustration. Using the mid peak preset of 0.157 dollars per kilowatt hour, an editable default to check against your own bill or the Ontario Energy Board, 930.75 multiplied by 0.157 equals 146.13 dollars, rounded to the nearest cent, for the energy portion in a year. If your lights are mostly on in off peak hours, use the off peak preset instead and the dollar figure will be lower. If they are mostly on in on peak hours, it will be higher.

This example shows why watt difference and hours both matter. A saving of 51 watts per bulb sounds small. Multiplied by ten bulbs, five hours a day, and 365 days, it becomes more than 900 kilowatt hours.

A note on what these examples leave out

Neither example includes delivery charges, regulatory charges, fixed monthly charges, taxes, or rebates, and neither assumes a heater or a set of lights runs exactly the same hours every day. Real use varies with weather, daylight, and routine. Treat every result as an estimate for comparison and planning, then confirm it against the kilowatt hours and line items on your next bill.

Practical ways to use this math at home

You do not need to audit every device. Focus on the largest draws and the longest run times. Make a short list, estimate each one for a typical week, and add them up. If the total is far below the kilowatt hours on your bill, you are missing a load, often space heating, water heating, a hot tub, an electric vehicle, or a dehumidifier that runs for many hours.

Timing shifts help only if the appliance can actually move. Laundry, dishwashing, and electric vehicle charging are often flexible. Cooking dinner and heating a room you are sitting in usually are not. The value of a shift is the kilowatt hours moved multiplied by the difference between the two rates. Using the presets in this guide, moving 10 kilowatt hours from on peak to off peak changes the energy portion by 10 multiplied by the difference between 0.203 and 0.098, which is 10 multiplied by 0.105, or 1.05 dollars. That helps you judge whether a routine change is worth it for your household.

Season matters too. A home that heats with electricity will use far more kilowatt hours in January than in June, even if daily habits do not change. Comparing a winter bill to a summer bill without noting the season can make it look like an appliance suddenly became expensive, when the real change was run time.

FAQ

How do I convert watts to kilowatt hours?

Divide watts by 1,000 to get kilowatts, then multiply kilowatts by the number of hours the appliance runs. For example, 1,000 watts is 1 kilowatt, and 1 kilowatt running for 3 hours uses 3 kilowatt hours. Multiply those kilowatt hours by your applicable rate to get the energy cost.

What is the difference between a kilowatt and a kilowatt hour?

A kilowatt measures power at a moment, how fast an appliance draws electricity while it is on. A kilowatt hour measures energy over time, how much was used in total. A 2 kilowatt heater running for half an hour uses 1 kilowatt hour, and a 1 kilowatt appliance running for a full hour also uses 1 kilowatt hour.

Why is my bill higher than kilowatt hours multiplied by the energy rate?

Because the energy rate is only one part of the bill. Delivery charges, regulatory charges, fixed monthly charges, taxes, and any applicable adjustments are added separately. Appliance calculators that use only the energy rate give you the energy portion, which is the right figure for comparing appliances and timing, but it will always be lower than the full bill impact.

Which time of use period is cheapest in Ontario?

In the calculator preset used in this guide, off peak is the lowest rate at 0.098 dollars per kilowatt hour, followed by mid peak at 0.157 dollars per kilowatt hour, and on peak at 0.203 dollars per kilowatt hour. These are editable defaults to check against your own bill or the Ontario Energy Board, and the clock hours for each period vary by season, so confirm both the rate and the schedule for your account.

How much does it cost to run a space heater for one hour?

At full power, a 1,500 watt heater is 1.5 kilowatts, so one hour uses 1.5 kilowatt hours. At the mid peak preset of 0.157 dollars per kilowatt hour, labelled as an editable default to check against your own bill or the Ontario Energy Board, the energy portion is 1.5 multiplied by 0.157, which equals about 24 cents for that hour, before delivery and other bill charges.

Do LED bulbs really save that much compared with older bulbs?

The saving comes from the watt difference multiplied by hours and by the number of bulbs. A single bulb swapped from 60 watts to 9 watts saves 51 watts while it is on. Over a few hours a day for one bulb, the saving is modest. Over ten bulbs, five hours a day, and a full year, the worked example in this guide shows a saving of 930.75 kilowatt hours, which is why whole home swaps show up on bills more clearly than a single bulb change.

Calculators and next steps

Use the Electricity Cost Calculator to enter your own watts, hours, and rate and test off peak, mid peak, and on peak cases side by side: https://mississippimaple.ca/tools/electricity-cost.html

Use the LED Savings Calculator to model a bulb swap for your own bulb count, wattages, and hours: https://mississippimaple.ca/tools/led-savings.html

Use the Hot Tub Running Cost Calculator if a heater and pump that cycle through the day are a large part of your bill: https://mississippimaple.ca/tools/hot-tub.html

Use the EV Charging Cost Calculator to estimate charging energy from distance, efficiency, and your rate: https://mississippimaple.ca/tools/ev-cost.html

Start with one appliance you are curious about, run the numbers with the rate from your own bill, and then check the result against your next bill. That single loop, estimate, run, and verify, teaches the method faster than estimating everything at once.

Sources and figures

Sources and figures note: Time of use structure and regulated rates are governed by the Ontario Energy Board. Distribution and delivery line items are set through your local utility under Ontario Energy Board oversight. Preset rates in this guide, off peak 0.098, mid peak 0.157, and on peak 0.203 dollars per kilowatt hour, are the Mississippi Maple calculator preset defaults, labelled throughout as editable defaults to check against your own bill or the Ontario Energy Board. No other prices, statistics, or rates are claimed in this guide. Appliance wattages in the examples are the stated example inputs, not averages for all homes.

Estimates only, verify before you buy materials. This guide plans quantities and costs; it does not replace local building codes, manufacturer instructions, or professional advice.