Time of Use (TOU) Calculator

Estimate your monthly electricity bill and potential savings on a Time of Use plan.

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Standard / Flat-Rate Plan

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Time of Use (TOU) Plan Details

Usage Distribution (%)

The sum of percentages must be 100%.

What is a Time of Use Calculator?

A time of use calculator is a specialized tool designed to help electricity consumers compare the cost of their energy usage between a traditional flat-rate plan and a Time of Use (TOU) plan. Instead of charging a single price for every kilowatt-hour (kWh) consumed, TOU plans have different rates depending on the time of day, day of the week, and sometimes the season. This calculator allows you to input your usage patterns and the specific rates for different time periods (on-peak, off-peak, etc.) to see which plan is more financially advantageous for your household.

The primary goal of a time of use calculator is to provide clarity on potential savings. By understanding how shifting energy-intensive activities—like running the dishwasher, doing laundry, or charging an electric vehicle—to off-peak hours can impact your monthly bill, you can make informed decisions about your electricity plan and consumption habits.

The Time of Use Formula and Explanation

The calculation is straightforward but requires breaking down your energy usage into the different rate periods defined by your utility provider. The calculator applies the standard cost formula: Cost = Energy Usage (kWh) × Rate ($/kWh) for each period.

Formulas Used:

1. Flat-Rate Cost Calculation:

Total Flat Cost = Total Monthly Usage (kWh) × Flat Rate ($/kWh)

2. Time of Use (TOU) Cost Calculation:

• On-Peak Cost = (Total Usage × % On-Peak) × On-Peak Rate
• Mid-Peak Cost = (Total Usage × % Mid-Peak) × Mid-Peak Rate
• Off-Peak Cost = (Total Usage × % Off-Peak) × Off-Peak Rate
• Total TOU Cost = On-Peak Cost + Mid-Peak Cost + Off-Peak Cost

3. Potential Savings Calculation:

Savings = Total Flat Cost - Total TOU Cost

The time of use calculator performs these calculations to give you a direct comparison. For a more accurate analysis, check your utility provider’s website for the exact hours and rates of each period.

Variables Table

Variable	Meaning	Unit	Typical Range
Total Monthly Usage	The total electricity consumed in a month.	kWh	300 – 2500 kWh
Flat Rate	A single, constant price for electricity.	$/kWh	$0.10 – $0.25
On-Peak Rate	The highest price for electricity during peak demand.	$/kWh	$0.20 – $0.50
Mid-Peak Rate	An intermediate price for electricity.	$/kWh	$0.12 – $0.30
Off-Peak Rate	The lowest price for electricity during low demand.	$/kWh	$0.05 – $0.15
Usage Percentage	The portion of energy used in each rate period.	%	0 – 100%

Practical Examples

Example 1: The Night Owl

A user who works from home during the day but consciously shifts heavy appliance usage to late at night.

• Inputs:
  • Total Usage: 1000 kWh/month
  • Flat Rate: $0.18/kWh
  • On-Peak Rate (4pm-9pm): $0.30/kWh | Usage: 15%
  • Mid-Peak Rate (7am-4pm): $0.20/kWh | Usage: 40%
  • Off-Peak Rate (9pm-7am): $0.10/kWh | Usage: 45%
• Results:
  • Flat-Rate Cost: 1000 kWh * $0.18 = $180.00
  • TOU Cost: (150 kWh * $0.30) + (400 kWh * $0.20) + (450 kWh * $0.10) = $45 + $80 + $45 = $170.00
  • Monthly Savings: $10.00

Example 2: The 9-to-5 Family

A family that is away during the day and does most of its cooking, cleaning, and entertainment during peak evening hours.

• Inputs:
  • Total Usage: 1200 kWh/month
  • Flat Rate: $0.18/kWh
  • On-Peak Rate (4pm-9pm): $0.30/kWh | Usage: 50%
  • Mid-Peak Rate (7am-4pm): $0.20/kWh | Usage: 20%
  • Off-Peak Rate (9pm-7am): $0.10/kWh | Usage: 30%
• Results:
  • Flat-Rate Cost: 1200 kWh * $0.18 = $216.00
  • TOU Cost: (600 kWh * $0.30) + (240 kWh * $0.20) + (360 kWh * $0.10) = $180 + $48 + $36 = $264.00
  • Monthly Loss: $48.00 (This family would be better off on a flat-rate plan).

These examples highlight why a time of use calculator is essential. Understanding your energy consumption patterns is key to saving money.

How to Use This Time of Use Calculator

1. Enter Total Monthly Usage: Find the total kWh from a recent electricity bill and enter it in the first field.
2. Input Your Flat Rate: If you know your current flat rate per kWh, enter it. This is the baseline for comparison.
3. Enter TOU Rates: Fill in the specific rates your utility charges for on-peak, mid-peak (if applicable), and off-peak periods. You can find these on your utility’s website.
4. Estimate Usage Distribution: This is the most critical step. Estimate what percentage of your electricity is used during each TOU period. If you’re unsure, start with a rough guess and adjust. For example, if you do laundry and run the dishwasher at night, your off-peak percentage will be higher.
5. Calculate and Analyze: Click “Calculate Savings.” The tool will display your estimated monthly cost on both plans and the difference. A positive number indicates savings on the TOU plan.
6. Interpret the Results: The results show whether your current habits are a good fit for a TOU plan. The bar chart provides a quick visual comparison of the two costs. Consider if you can shift more usage to off-peak times to increase savings.

Key Factors That Affect Time of Use Savings

• Lifestyle Flexibility: The ability to shift when you use major appliances is the single biggest factor. If you can do laundry, run the dishwasher, or charge your EV overnight, you’ll benefit most.
• Appliance Types: High-consumption appliances like HVAC systems, electric water heaters, clothes dryers, and electric vehicle chargers have the largest impact on your bill.
• Utility Rate Spreads: The difference between on-peak and off-peak rates is crucial. The larger the spread, the greater the potential for savings. A plan with a $0.25/kWh difference offers more opportunity than one with a $0.05/kWh difference.
• Peak Hour Timing: Your utility defines when peak hours occur. If their peak hours are 4 PM to 9 PM, but you do most of your cooking from 6 PM to 7 PM, it will be challenging to avoid higher costs without changing habits.
• Seasonal Changes: Energy use for heating and cooling changes dramatically between summer and winter, which can alter your usage patterns and savings. Some utilities have different TOU rates for different seasons.
• Smart Home Technology: Using smart thermostats, appliance timers, or a home energy management system can automate the process of shifting usage to off-peak hours, maximizing your savings effortlessly.

Frequently Asked Questions (FAQ)

1. When are peak and off-peak hours?

This varies by utility and region, but generally, on-peak hours are late afternoon to early evening on weekdays (e.g., 4 PM – 9 PM) when demand is highest. Off-peak hours are typically late at night, early morning, and all day on weekends and holidays. Always check with your specific provider.

2. Can a time of use plan make me pay more?

Yes. If your lifestyle requires significant energy use during on-peak hours and you cannot shift it, a TOU plan could increase your monthly bill. This is why using a time of use calculator before switching is so important.

3. What is the main benefit of TOU plans?

The main benefit is the potential for significant cost savings if you can align your energy use with off-peak hours. It also helps reduce strain on the electrical grid, which can improve reliability for everyone and support the integration of renewable energy.

4. How do I find my home’s energy usage data?

Your monthly utility bill is the best source. Many providers also offer online portals with detailed hourly or daily usage data, which is perfect for accurately filling out a time of use calculator.

5. Is a TOU plan good for electric vehicle (EV) owners?

Absolutely. TOU plans are often very beneficial for EV owners, as they can schedule their vehicle to charge overnight during the cheapest off-peak hours, leading to substantial savings compared to a flat-rate plan.

6. What’s the difference between TOU and Tiered rates?

TOU rates are based on *when* you use energy. Tiered rates are based on *how much* energy you use in a month. With tiered rates, your per-kWh price increases after you exceed certain usage thresholds, regardless of the time of day.

7. Does solar panel ownership affect TOU savings?

Yes. Solar panels generate the most power during the day, which can coincide with mid-peak or even on-peak hours, reducing the amount of expensive grid power you need to buy. Pairing solar with battery storage allows you to store that solar energy to use during peak evening hours, maximizing savings even further. Our solar ROI calculator can help estimate this.

8. How accurate is this calculator?

This calculator provides a reliable estimate based on the data you provide. Accuracy depends on how correctly you input your total usage, rates, and especially your usage distribution across the different time periods. For a perfect calculation, you’d need precise hourly data from your utility.

Related Tools and Internal Resources

Explore other calculators and resources to take full control of your energy and finances:

• Appliance Electricity Cost Calculator: Find out how much a specific appliance costs to run.
• EV Charging Cost Calculator: Estimate the cost to charge your electric vehicle at home.
• Renewable Energy Guide: Learn about different green energy options for your home.