TOU vs ULO Ontario — Rate Plan Comparison
Compare Time-of-Use and Ultra-Low Overnight rate plans for solar panel and battery storage systems. Find out which plan saves you more.
Rate Plan Comparison
| Feature | Time-of-Use (TOU) | Ultra-Low Overnight (ULO) |
|---|---|---|
| Off-Peak Rate | 9.8¢/kWh (7PM-7AM + weekends) | 9.8¢/kWh (weekends/holidays only) |
| Ultra-Low Rate | N/A | 3.9¢/kWh (11PM-7AM daily) |
| Mid-Peak Rate | 15.7¢/kWh (11AM-5PM) | 15.7¢/kWh (7AM-4PM, 9-11PM) |
| On-Peak Rate | 20.3¢/kWh (7-11AM, 5-7PM) | 39.1¢/kWh (4-9PM weekdays) |
| Peak-to-Low Ratio | 2.1x (20.3¢ ÷ 9.8¢) | 10.0x (39.1¢ ÷ 3.9¢) |
| Best For (No Solar) | Average households | EV owners, night shift workers |
| Best For (Solar Only) | Better export value during peaks | Higher savings during peak offset |
| Best For (Solar + Battery) | Moderate arbitrage savings | Maximum arbitrage (10x spread) |
| Battery Payback | 7-10 years | 3-5 years |
Hourly Rate Breakdown (Weekdays)
Compare rates hour-by-hour to understand the best battery strategy for each plan.
| Time | TOU Rate | ULO Rate | Battery Strategy |
|---|---|---|---|
| 12AM-7AM | 9.8¢ (Off-Peak) | 3.9¢ (Ultra-Low) | Charge battery on ULO |
| 7AM-11AM | 20.3¢ (On-Peak) | 15.7¢ (Mid-Peak) | Solar production starts |
| 11AM-4PM | 15.7¢ (Mid-Peak) | 15.7¢ (Mid-Peak) | Peak solar production |
| 4PM-5PM | 15.7¢ (Mid-Peak) | 39.1¢ (On-Peak) | ULO: Discharge battery! |
| 5PM-7PM | 20.3¢ (On-Peak) | 39.1¢ (On-Peak) | Both: High value period |
| 7PM-9PM | 9.8¢ (Off-Peak) | 39.1¢ (On-Peak) | ULO: Keep discharging |
| 9PM-11PM | 9.8¢ (Off-Peak) | 15.7¢ (Mid-Peak) | Prepare for overnight |
| 11PM-12AM | 9.8¢ (Off-Peak) | 3.9¢ (Ultra-Low) | ULO: Start charging |
Annual Savings Comparison
Scenario 1: No Solar, No Battery
Average household using 10,000 kWh/year with typical usage patterns.
TOU cost: ~$1,400/yr
ULO cost: ~$1,350/yr
ULO saves ~$50/yr
Scenario 2: Solar + Battery (16 kWh)
8 kW solar system + 16 kWh battery with peak shaving strategy.
TOU savings: ~$1,800/yr
ULO savings: ~$2,600/yr
ULO saves ~$800/yr more
Scenario 3: Battery Only (No Solar)
16 kWh battery for pure arbitrage (no solar panels).
TOU savings: ~$400/yr
ULO savings: ~$1,800/yr
ULO saves ~$1,400/yr more
Which Plan Should You Choose?
Choose TOU if:
- You don't have a battery or EV
- You use most electricity during daytime
- You have solar panels with net metering
- You can't shift major usage to overnight
Choose ULO if:
- You have a battery for peak shaving
- You own an EV that charges overnight
- You can shift laundry/dishwasher to night
- You want maximum solar + battery savings
Model Your Savings on Both Plans
Our peak shaving calculator compares TOU and ULO savings with your specific system and usage.
Try Peak Shaving CalculatorFrequently Asked Questions
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