Is Ultra-Low Overnight Worth It? ULO vs TOU Math for Ontario Homes

Ultra-Low Overnight (ULO) is worth it for Ontario households that can move a lot of electricity use, typically EV charging, into the 11 p.m. to 7 a.m. window at 3.7¢/kWh while keeping weekday use from 4 to 9 p.m. low. For a typical 700 kWh home that changes nothing, our estimate shows ULO costing about $22 a month more than Time-of-Use (TOU), because the 37.7¢ on-peak price outweighs the cheap overnight hours.

ULO is one of three Regulated Price Plan options set by the Ontario Energy Board, alongside TOU and Tiered. Most local distribution companies (LDCs) have offered it since 2023. Here is how the numbers work.

ULO and TOU prices side by side

Prices in effect 1 November 2026 to 31 October 2027:

ULO period	Hours	Price	TOU equivalent at that time (winter)
Ultra-low overnight	11 p.m.–7 a.m. every day	3.7¢	Off-peak 9.1¢
Weekend off-peak	7 a.m.–11 p.m. weekends and holidays	9.1¢	Off-peak 9.1¢
Mid-peak	Weekdays 7 a.m.–4 p.m. and 9–11 p.m.	14.6¢	Mix of on-peak, mid-peak and off-peak
On-peak	Weekdays 4–9 p.m.	37.7¢	Mid-peak 4–5 p.m., on-peak 5–7 p.m. (18.9¢), off-peak 7–9 p.m.

ULO is cheaper than TOU for 8 hours a night and the same on weekend days. It is more expensive for most of the weekday, and roughly double TOU's highest price during the five-hour evening peak.

Is Ultra-Low Overnight worth it? Three example homes

These are commodity-only estimates for a winter month. Delivery and regulatory charges are largely the same on either plan. The usage splits are our assumptions for illustration; your own split will differ.

Home A: typical 700 kWh, gas heat, no changes. On TOU, we assume 64% off-peak, 18% mid-peak and 18% on-peak. On ULO, we assume 28% overnight, 20% weekend daytime, 32% mid-peak and 20% in the 4–9 p.m. peak.

Plan	Calculation	Commodity cost
TOU	448 × 9.1¢ + 126 × 14.6¢ + 126 × 18.9¢	$82.98
ULO	196 × 3.7¢ + 140 × 9.1¢ + 224 × 14.6¢ + 140 × 37.7¢	$105.48
Difference		ULO costs about $22.50 more

Home B: same home plus an EV charging 400 kWh a month after 11 p.m., and 50 kWh of dishwasher and laundry moved out of the evening peak to overnight. That is about 2,000–2,500 km of driving a month at 16–20 kWh/100 km.

Plan	Calculation	Commodity cost
TOU	$82.98 + 400 × 9.1¢	$119.38
ULO	646 × 3.7¢ + 140 × 9.1¢ + 224 × 14.6¢ + 90 × 37.7¢	$103.28
Difference		ULO saves about $16 a month, or about $190 a year

Home C: heat pump home, 1,800 kWh in a cold month, with heating running through the evening. Same percentage splits as Home A.

Plan	Calculation	Commodity cost
TOU	1,152 × 9.1¢ + 324 × 14.6¢ + 324 × 18.9¢	$213.37
ULO	540 × 3.7¢ + 360 × 9.1¢ + 540 × 14.6¢ + 360 × 37.7¢	$267.30
Difference		ULO costs about $54 more

The break-even rule of thumb

Two numbers do most of the work:

• Every kWh moved from the 4–9 p.m. weekday peak to overnight saves 34¢ on ULO (37.7¢ − 3.7¢).
• Every kWh of overnight EV charging saves 5.4¢ on ULO compared with TOU off-peak (9.1¢ − 3.7¢).

In Home A, the ULO penalty was about $22.50. To make that up with EV charging alone, you would need roughly 22.50 ÷ 0.054 = about 415 kWh of overnight charging a month, or around 2,300 km of driving. Moving just 66 kWh a month out of the evening peak would cover the same gap (22.50 ÷ 0.34). In practice, the households that do best on ULO do both.

Who should consider ULO

Good candidates:

• EV owners who charge overnight with a scheduled Level 2 charger. See EV charging cost in Ontario.
• Households who are out from 4 to 9 p.m. on weekdays, or can push cooking, laundry and dishwashing later.
• Homes with a battery that can be charged overnight and discharged in the evening.

Poor candidates:

• Electric baseboard and heat pump homes that heat through winter evenings.
• Families who cook, bathe and do laundry between 4 and 9 p.m. on weekdays with an electric water heater or range.
• Anyone who works from home in a space heated or cooled electrically and cannot shift that load.

Caution: Air conditioning on hot summer weekday afternoons and evenings runs straight into the ULO on-peak. Pre-cooling the house before 4 p.m. helps, but a heat wave can quickly cancel a month of overnight savings.

How to decide

1. Download 12 months of hourly data from your LDC account (often through Green Button).
2. Add up use by ULO period, or use our electricity price plan calculator.
3. Ask your LDC whether it offers ULO, how switching works, how soon it takes effect and how easily you can switch back.
4. Set timers before you switch, so the EV, dishwasher and laundry already run at the right times. See the best time to run the dishwasher and laundry.

For a fuller comparison of all three plans, read our guide to Ontario electricity price plans. All figures here are estimates; confirm prices at oeb.ca (opens in a new tab).