For an Ontario household charging an EV at home, Ultra-Low Overnight almost always beats Time-of-Use and Tiered. The plan exists because the grid needs a price signal that pushes EV charging into the quiet 11pm to 7am window. Use a timer and the savings show up automatically. Charge during the wrong window and the same plan punishes you.
Overnight, weekend off-peak, weekday mid-peak and weekday on-peak. The overnight rate is 3.9¢/kWh from 11pm to 7am every single day, including weekends.
A Level 2 charger pulls a typical daily commute back into the battery in 4 to 5 hours. Set the timer to start at 11pm and the entire session lands at 3.9¢/kWh, about a third of TOU off-peak.
Weekday afternoons cost 39.1¢/kWh, almost twice the TOU on-peak rate. Run a dishwasher or central AC during this window and the savings on the EV start unwinding fast.
The headline number: a typical EV driving 17,000 km/year uses around 7,200 kWh just for the car. ULO at 3.9¢/kWh costs about $281/year in commodity for that. TOU costs $700 to $972. Net savings on the EV alone: usually $400 to $700 per year.
ULO punishes the wrong habits even harder than TOU does. The two patterns we see most often:
Each of these is a one-time setup that pays itself back in months, but most ULO households never do them.
"ULO is just for EV owners."
The name "Ultra-Low Overnight" suggests a plan designed for one specific niche. That framing is half right and almost entirely misleading. ULO is built around a consumption shape, not an appliance. Any household whose load is heavy overnight and on weekends, and light during the 4pm to 9pm weekday window, will save on ULO. That includes electric water heaters on a timer, electric thermal storage heating, freezers and pool pumps on overnight cycles, and households where everyone is out at work or school during late afternoons.
The opposite is also true and far less often discussed. A household where the heaviest hours sit squarely in the weekday 4pm to 9pm window (someone home running the AC, cooking dinner, doing laundry) will lose money on ULO compared to TOU. The 39.1¢/kWh on-peak rate is roughly twice the TOU on-peak rate of 20.3¢/kWh. ULO is not a free upgrade. It is a tool that magnifies whichever consumption habit you already have.
How ULO is engineered, and when it wins
The Ontario Energy Board added Ultra-Low Overnight to the Regulated Price Plan to give the grid a sharper behavioural lever than Time-of-Use. TOU uses three rates and a relatively soft on-peak / off-peak gap (about 2x). ULO uses four rates and an aggressive gap (the on-peak rate is ten times the overnight rate). The deeper trough rewards shifting load into the quiet hours; the higher peak penalises running through the system stress window.
For an EV household, the structural fit is almost perfect. Most home charging happens at night anyway, the battery does not care when the electrons arrive, and a Level 2 charger plus a timer makes the whole thing automatic. Once the timer is set, the savings accrue every single day without any further decision. That is the rare household-level intervention that compounds while you sleep.
Where ULO stops winning is when a household has both significant late-afternoon load and limited flexibility to shift it. Shift workers, families with someone at home running AC through summer afternoons, or homes with electric cooking and laundry that cannot move out of the 4pm to 9pm window will see ULO punish them on the peak side faster than the overnight side rewards them. The math is genuinely asymmetric.
ULO rates and when each one applies
The same four prices apply across every OEB-regulated electricity distributor in Ontario. The schedule is fixed and does not change with the seasons (TOU shifts the on-peak window between winter and summer; ULO does not).
| Period | Hours | Rate | Notes |
|---|---|---|---|
|
Overnight
|
Every day, 11pm to 7am | 3.9¢/kWh | Best window for EV charging, electric water heater on a timer, electric heat overnight, dishwasher delay-start. |
|
Weekend off-peak
|
Sat, Sun and statutory holidays, 7am to 11pm | 9.8¢/kWh | Identical to the TOU off-peak rate. Safe for laundry, cooking and EV top-ups on weekend days. |
|
Mid-peak
|
Weekdays 7am to 4pm and 9pm to 11pm | 15.7¢/kWh | Same as the TOU mid-peak rate. The 9pm to 11pm sliver is when you wait out before the overnight window opens. |
|
On-peak
|
Weekdays 4pm to 9pm | 39.1¢/kWh | The trap. Roughly twice TOU on-peak, ten times the ULO overnight rate. Avoid dishwasher, dryer, AC and EV charging in this window. |
Where ULO households quietly leak money
A ULO bill misbehaves in five recurring ways. None of them are about the EV. They are about everything else that runs through the 4pm to 9pm window without anyone noticing.
The single most expensive mistake on ULO. A 7 kWh/hour charger running from 5pm to 9pm pulls 28 kWh at 39.1¢/kWh. That single evening costs $10.95, vs $1.09 if the same 28 kWh had landed after 11pm.
A typical cycle uses ~1.5 kWh of electricity (mostly heating the water in the unit). At 39.1¢/kWh that is 59¢ per cycle, vs 6¢ at overnight. Multiply by 4 cycles/week and that habit alone is ~$110/year.
A 3 kW AC unit running 4 hours through the on-peak window costs $4.69/day at ULO on-peak, vs $0.47 if shifted to run overnight. Pre-cooling the house before 4pm and letting it drift is the workaround.
A heat-pump dryer uses ~2 kWh per load; a vented dryer ~3 kWh. Running it from 7pm to 8:30pm costs $1.17 vs $0.12 if delayed to 11pm. The delay-start button pays for itself in three loads.
Roasting a meal in an electric oven for 90 minutes uses ~3 kWh. At ULO on-peak that is $1.17 vs $0.30 at TOU off-peak. Not life-changing per meal but it adds up.
ULO savings calculator for EVs
Pick your monthly consumption, the share that goes to EV charging, and when you actually charge. The calculator compares the same household on TOU and on ULO with current OEB regulated rates.
EV + ULO calculator
Three quick choices. See your annual difference vs TOU.
The math works. Keep the timer set and avoid the weekday 4pm to 9pm window for dishwashers, dryers and AC.
Charging in the wrong window is the problem. Install a Level 2 charger with a timer set to start at 11pm. The same EV consumption shifted overnight flips this calculation by hundreds of dollars per year.
Close call. Auditing your weekday 4pm to 9pm habits would push ULO into clear-win territory.
Make the three selections to see your TOU vs ULO comparison.
Commodity rates only; delivery, regulatory and HST add separately, and the OER 23.5% discount applies before HST. Assumes the same non-EV load shape on both plans; actual mileage varies by household.
A timer pays for itself faster than the EV does
A typical electric vehicle uses around 20 kWh per 100 km. At 17,000 km/year, that is roughly 7,200 kWh just to keep the car moving. On the ULO overnight rate (3.9¢/kWh), that energy costs about $281/year in commodity. On the TOU off-peak rate (9.8¢/kWh), the same energy costs about $706. If half the charging spills into mid-peak, TOU climbs to roughly $972. The gap between disciplined ULO and average TOU is somewhere between $400 and $700 per year on the EV alone.
The non-obvious bit is what happens to that math when ULO is run badly. The 39.1¢/kWh on-peak rate is not just a number on a rate card; it is roughly ten times the overnight rate. A single 28 kWh EV charge done by mistake between 5pm and 9pm costs about $11 in commodity. The same 28 kWh charge done after 11pm costs about $1.09. One week of evening charging unawares can erase a month of overnight savings.
A Level 2 charger installed for $500 to $1,200 with a timer set to start at 11pm pays itself back in 12 to 18 months for a typical Ontario EV household. The timer itself adds maybe $50 to the install. It is the cheapest single piece of equipment in the entire EV setup, and the one piece that most directly decides whether ULO works.
What to actually do, in order
- Confirm you have a smart (interval) meter. Almost every Ontario home does; the meter has a small digital display and your bill shows hour-by-hour usage if you log into the LDC portal. ULO requires interval data to bill the four periods correctly.
- Install a Level 2 charger. 240-volt, 30-amp circuit, typically $500 to $1,200 for the parts and a licensed electrician. Some LDCs run annual Level 2 rebate programs worth checking before booking the work.
- Set the charger or the car timer for 11pm to 7am. Either the wall charger has a built-in delay-start, or the car does. Both work. The point is that you never have to think about it again.
- Audit your 4pm to 9pm weekday habits. Use the delay-start on the dishwasher and the dryer. Pre-cool the house with the AC before 4pm, then let it drift. Move evening cooking earlier or onto the weekend.
- Request the switch from your LDC. Call, email or use the online portal. The change is free and takes effect on the next meter read. You can switch back twice in a 12-month window if it does not fit your household after all.
- Check your bill 60 days in. Your portal will show how many kWh landed in each ULO period. The healthy split is heavy overnight, light on-peak. If on-peak is more than 15% of your monthly kWh, audit the weekday 4pm to 9pm window again.
The only province with an ultra-low overnight rate, at exactly the right time
Ontario is the only Canadian province with a dedicated ultra-low overnight regulated rate. Quebec has a low base price but no overnight tier worth the name. Alberta is fully deregulated and a fixed retailer contract has to be hand-shopped. The Atlantic provinces and the Prairies use simpler flat or tiered rates without an overnight differential. The structural opportunity sitting inside ULO is genuinely a provincial feature.
EV adoption in Ontario is climbing, and overnight load is climbing with it. The grid needs the price signal to flatten the curve and avoid building expensive peaking capacity. That is the design intent behind ULO and the reason the on-peak rate is set deliberately high. The plan is a behavioural tool, not a tariff accident.
ULO uptake is still well under 10% of Regulated Price Plan customers, even among EV owners. Most EV households default to TOU when their smart meter is installed and never revisit the choice. That gap (between the EV households that switched and the ones that did not) is hundreds of dollars per year per household, year after year. Closing it is one of the cleanest single decisions an Ontario EV owner can make.
