TOU vs ultra-low overnight vs tiered in Ontario: which plan is cheaper for you?

Which Ontario RPP plan is cheapest depends on when you use electricity and how much. With prices from 1 November 2026, tiered costs 11.2¢ per kWh up to the threshold; time-of-use averages close to that for a typical household; and ultra-low overnight (ULO) only wins if a large share of your use falls between 11 p.m. and 7 a.m. while little falls in the 4–9 p.m. weekday window at 37.7¢. As a rule of thumb from the arithmetic below: if your TOU average is above 11.2¢ and you stay under the tier threshold, tiered is cheaper; and ULO only comes out ahead when your overnight use is several times your weekday 4–9 p.m. use, because compared with tiered each kWh in that window costs as much extra as about 3.5 overnight kWh save.

This guide is part of comparing electricity plans with worked examples. Prices are explained in Ontario RPP prices from 1 November 2026.

The prices you are comparing (from 1 November 2026)

Tier threshold for homes: 1,000 kWh/month in winter, 600 kWh/month in summer.

Step 1: find your split

Your distributor's online account shows kWh by TOU period. For ULO, the periods are different, so you need hourly data: most distributors provide it through Green Button downloads or the usage charts. Roughly sort your use into:

• overnight 11 p.m.–7 a.m. (all days);
• weekend and holiday daytime 7 a.m.–11 p.m.;
• weekday 4–9 p.m.;
• weekday other hours (7 a.m.–4 p.m. and 9–11 p.m.).

Step 2: compute an average price for each plan

TOU average = off% × 9.1 + mid% × 14.6 + on% × 18.9

ULO average = overnight% × 3.7 + weekend day% × 9.1 + weekday other% × 14.6 + weekday 4–9 p.m.% × 37.7

Tiered average = 11.2¢ if you stay under the threshold; otherwise (threshold × 11.2 + excess × 13.2) ÷ total kWh.

Then use the plan comparison tool to turn averages into dollars.

Worked examples (illustrative households)

Household A: works from home, no EV, 750 kWh in January

Split on TOU: 60% off-peak, 22% mid-peak, 18% on-peak. TOU = 0.60 × 9.1 + 0.22 × 14.6 + 0.18 × 18.9 = 5.46 + 3.21 + 3.40 = 12.07¢.

ULO split: 28% overnight, 16% weekend day, 40% weekday other, 16% weekday 4–9 p.m. ULO = 1.04 + 1.46 + 5.84 + 6.03 = 14.36¢.

Tiered: 750 kWh is under 1,000 → 11.2¢.

Tiered wins by about $6.56 a month over TOU.

Household B: EV charged overnight, 1,100 kWh in January

The EV adds about 350 kWh, all after 11 p.m. ULO split: 50% overnight, 12% weekend day, 28% weekday other, 10% weekday 4–9 p.m. ULO = 1.85 + 1.09 + 4.09 + 3.77 = 10.80¢.

TOU split: 72% off-peak, 14% mid-peak, 14% on-peak. TOU = 6.55 + 2.04 + 2.65 = 11.24¢.

Tiered: 1,000 × 11.2¢ + 100 × 13.2¢ = $125.20, average 11.38¢.

ULO wins by about $4.86 over TOU. If the household also moved the dishwasher and laundry out of 4–9 p.m. and pushed the on-peak share down to 6%, ULO would drop to about 9.9¢ and save more.

Household C: retired, home all day, high evening use, 520 kWh in July

Summer TOU: on-peak is 11 a.m.–5 p.m. weekdays. Split: 58% off, 20% mid, 22% on. TOU = 5.28 + 2.92 + 4.16 = 12.36¢ → $64.27. Tiered: 520 kWh is under the summer 600 kWh threshold → $58.24. ULO with 22% weekday 4–9 p.m. use would cost even more. Tiered wins.

The break-even logic in one paragraph

Compared with tiered at 11.2¢, TOU saves 2.1¢ on each off-peak kWh but costs 3.4¢ more on each mid-peak and 7.7¢ more on each on-peak kWh. ULO saves 7.5¢ per overnight kWh against tiered but costs 26.5¢ more on each weekday 4–9 p.m. kWh. So every kWh moved out of 4–9 p.m. on ULO is worth about 3.5 overnight kWh. That ratio is the key fact to remember when you think about ULO.

When to switch, and how

• Switch requests go to your local distributor; many have an online form. Changes apply from a future meter read.
• Re-check each season: the TOU on-peak window and the tier threshold change on 1 May and 1 November.
• Re-check when your household changes: an EV, a heat pump, a new baby, retirement.

Mistakes to avoid

• Moving to ULO for "cheap nights" without data. Evening cooking and laundry at 37.7¢ add up fast.
• Ignoring the tier threshold. A summer month at 900 kWh puts 300 kWh at 13.2¢.
• Comparing with a retailer offer. Retail contracts are a different decision: see fixed contracts vs the default.

If you are adding an EV, read home EV charging costs by plan; to rebuild a whole bill around your choice, use estimating a monthly bill from kWh.

FAQ

Can I switch back if the new plan costs more?

Yes. You can switch between TOU, ULO and tiered by asking your distributor; check how soon changes take effect.

Is the OEB's bill calculator better than doing this myself?

It uses your inputs and current prices and is a good cross-check; the method here lets you test what-if scenarios.

Do delivery charges change between plans?

No. Only the energy line changes.

Does the plan affect the Ontario Electricity Rebate?

Only indirectly: the rebate is 15.7% of the pre-tax subtotal, which is slightly larger when the energy cost is higher.

Sources

• Ontario Energy Board — RPP prices, periods and bill calculator
• Hydro One — posted prices and periods effective 1 November 2026
• Independent Electricity System Operator — why prices vary by time of day