Ontario electricity guide
TOU vs Tiered vs ULO Calculator
Updated 2026‑04‑22
This calculator compares Time‑of‑Use (TOU), Tiered, and Ultra‑Low Overnight (ULO) pricing using your estimated monthly usage and how your kWh are spread across time periods. Enter your assumptions and see which plan is likely cheapest for your household.
Your usage
TOU usage split (percent)
If your split doesn’t add to 100, it will normalize automatically.Tiered pricing
Rates (enter your assumptions)
TOU rates
ULO rates
ULO usage split (percent)
ULO adds an ultra‑low overnight period. If unsure, start with a guess and adjust.Other bill components (estimates)
Tip: If you charge an EV or run large appliances overnight, increase your ULO “ultra‑low overnight %” and see how the result changes.
How to use this tool
- Use your monthly kWh from your bill.
- Estimate your time‑period split. If unsure, start with a rough guess.
- Enter rates you want to test — these change over time.
- Keep delivery/GA close to your typical bill so totals feel realistic.
Educational estimator only. For official rate periods and current prices, consult your utility or the Ontario Energy Board.
What is the difference between TOU, Tiered, and ULO?
Ontario households can choose from three electricity pricing structures, and each one rewards different usage patterns. Time‑of‑Use (TOU) pricing changes the electricity rate depending on the time of day. Tiered pricing keeps things simpler by charging one rate up to a monthly usage threshold and a higher rate above it. Ultra‑Low Overnight (ULO) pricing adds a deeply discounted overnight period, which can be helpful for households that can shift meaningful usage into late‑night hours.
This means the “best” plan depends less on the size of your home and more on when you use electricity. A household that charges an electric vehicle overnight may benefit from ULO, while a household with steady daytime usage may prefer Tiered or TOU depending on its patterns.
Why timing matters as much as total usage
Two households may use the same total kWh in a month and still pay different amounts if one runs major appliances during on‑peak periods and the other shifts more usage into off‑peak or overnight periods. Timing can influence the energy portion of the bill almost as much as total consumption.
This calculator helps you test different assumptions and see whether shifting flexible loads — such as laundry, dishwashing, or EV charging — could change which pricing plan is cheapest.
What this calculator does and does not show
This calculator is designed as an educational planning tool. It helps compare likely monthly totals under TOU, Tiered, and ULO assumptions using estimated rates, usage splits, delivery charges, and Other amount shown separately on your bill values.
It does not replace a real utility bill. Actual Ontario electricity bills depend on current rate schedules, seasonal thresholds, local utility delivery structures, and regulatory adjustments that can change over time. Use this tool to compare scenarios, not to predict an exact invoice amount to the penny.
When ULO pricing may make sense
ULO pricing is often most attractive for households that can consistently use electricity during ultra‑low overnight periods. This may include homes with electric vehicles, programmable water heating, or appliances that can be scheduled late at night. If overnight usage is only a small share of the household total, ULO may not outperform TOU or Tiered pricing.
A good way to test this is to increase the overnight percentage in the calculator and compare the results. If the gap remains small, the added complexity of changing habits may not be worth it. If the savings become meaningful, the pricing change may deserve closer consideration.
Related Ontario electricity guides
- TOU vs Tiered pricing explained
- How Ontario electricity billing works
- Why delivery charges can be high
- Other amount shown separately on your bill explained
- Ontario Electricity Ultimate Guide