Time-of-Use Rates for EV Charging: How They Work

Time-of-use (TOU) rates for EV charging can lower your charging costs when you move most of your charging into lower-price hours. The main catch is that peak and off-peak windows are not the same everywhere. Your savings depend on your utility, rate plan, season, EV efficiency, charger speed, and how much other electricity your home uses during peak hours.

What Are Time-of-Use (TOU) Rates for EV Charging?

Time-of-use rates are electricity plans where your price per kilowatt-hour changes by time of day. Instead of paying one flat rate all day, you may pay more during high-demand hours and less during off-peak hours.

For EV charging, that matters because your car may use more electricity than most single household appliances. The U.S. Department of Energy’s Alternative Fuels Data Center notes that actual residential EV charging costs depend on your electricity cost, vehicle efficiency, equipment, time of day, and charging duration. Some utilities also offer TOU rates or other charging incentives.

A TOU plan does not stop you from charging during peak hours. It simply changes the price. If your EV or charger lets you schedule charging, you can plug in when you get home and delay charging until the cheaper window begins.

How TOU Rates Change EV Charging Costs

The easiest way to understand TOU charging is to calculate your cost per 100 miles. You only need two numbers:

1. Your EV efficiency: Find the vehicle’s kWh per 100 miles on its window sticker, owner information, or FuelEconomy.gov.
2. Your electricity rate: Use the cents-per-kWh price from your utility plan for the hours when the EV charges.

Use this formula:

EV kWh per 100 miles × electricity price per kWh = charging cost per 100 miles.

For example, if your EV uses 30 kWh per 100 miles and your off-peak rate is $0.25/kWh, your cost is $7.50 per 100 miles before charging losses. If the same charging happens at $0.55/kWh, the cost is $16.50 per 100 miles.

For a more realistic estimate, add a small buffer for charging losses. FuelEconomy.gov notes that battery charging efficiency can vary, often around 84% to 93%. That means some electricity is lost as heat or conversion loss before it reaches the battery.

Peak vs. Off-Peak Hours for EV Charging

Peak hours are the high-price periods when the grid is under more demand. Off-peak or super-off-peak hours are lower-price periods when demand is lower or supply is easier to manage.

Do not assume one national schedule. Current utility examples show why:

• PG&E EV2-A: PG&E lists off-peak hours as 12 midnight to 3 p.m., peak hours from 4 to 9 p.m., and partial-peak hours from 3 to 4 p.m. and 9 p.m. to midnight on its EV2-A plan.
• Southern California Edison TOU-D-PRIME: SCE advises EV customers to charge between 8 a.m. and 4 p.m. and avoid using energy between 4 p.m. and 9 p.m.
• San Diego Gas & Electric EV plans: SDG&E lists several EV and electric-home plans with 4 to 9 p.m. on-peak periods, plus off-peak and super-off-peak windows that vary by plan.

These are examples, not rules for every driver. Your local utility may use different hours, seasonal calendars, weekend pricing, holidays, baseline allowances, or a separate EV meter.

Real-World Impact of TOU Rates on EV Charging Costs

TOU rates can lower your EV charging cost, but the real impact depends on how much charging you can move out of peak hours. If you already charge overnight or during a lower-price midday window, a TOU plan may fit your habits. If you often need quick charging during early evening peak hours, the plan may save less or even cost more.

Cost Savings Potential

To estimate monthly savings, calculate the same charging amount under two prices:

1. Estimate your monthly EV energy use. Example: 1,000 miles per month × 30 kWh per 100 miles = 300 kWh per month.
2. Multiply that by your off-peak rate. Example: 300 kWh × $0.25 = $75.
3. Multiply the same kWh by your peak rate. Example: 300 kWh × $0.55 = $165.
4. The difference is your potential charging savings if you can move all that charging from peak to off-peak. In this example, it is $90 per month.

This is only an example. Your actual savings may be much lower if your rate spread is smaller, your EV is efficient, you drive fewer miles, or your charger still runs during peak hours.

Whole-Home Rate Tradeoffs

Some EV TOU plans apply to your whole home. That can be helpful if you can also shift laundry, dishwashing, pre-cooling, and battery charging away from peak hours. But it can backfire if your household uses a lot of electricity during peak periods for air conditioning, cooking, medical equipment, or work-from-home needs.

Before switching, review at least three months of bills if your utility provides hourly usage data. A full year is better because summer and winter rates can differ.

Separate EV Meter vs. Whole-Home TOU

Some utilities offer a separate EV meter option. This can separate vehicle charging costs from household electricity use, but it may require meter work, extra equipment, and a different monthly charge. A whole-home plan is simpler, but all household electricity may be billed under the TOU schedule.

Compare both options if your utility offers them. The best plan is not always the one with the lowest off-peak EV rate. It is the one with the lowest total bill after your home and vehicle usage are included.

Benefits of Charging During Off-Peak Times

Lower Electricity Costs

The biggest benefit is cost control. EV charging is flexible because your vehicle often sits parked for hours. When your charger can wait until the low-price period, you may reduce your cost per mile without changing how far you drive.

Better Grid Timing

Off-peak charging can also help reduce strain during high-demand hours. ENERGY STAR explains that some connected EV chargers can support remote monitoring and control, and some smart-grid-ready products may help households or property managers participate in utility savings programs.

More Predictable Home Charging

Once your schedule is set, home charging becomes easier. You can plug in when you park, let the car wait, and wake up with the battery level you need.

Smart Charging Strategies for Maximizing Savings

Smart charging means using your vehicle app, charger app, or utility program to control when the car charges. Many EVs and home chargers let you set a start time, departure time, charge limit, or preferred charging window.

1. Set the off-peak window. Enter your utility’s cheapest hours into your vehicle or charger app.
2. Use a departure time. Tell the car when you need to leave so it can finish charging before then.
3. Set a daily charge limit. Many drivers do not need 100% every day. Follow your vehicle manufacturer’s battery guidance.
4. Check the first few sessions. Review your utility usage or charger history to confirm charging started during the right window.
5. Update settings when seasons change. Some TOU plans change rates or hours in summer and winter.

Level 1 vs. Level 2 Charging on TOU Rates

Your charger speed affects how well TOU scheduling works.

Level 1 charging uses a standard 120-volt outlet. ENERGY STAR says Level 1 charging often adds about 2 to 5 miles of range per hour. It may work if you drive short distances and have a long off-peak window.

Level 2 charging uses 240 volts and usually adds range much faster. ENERGY STAR lists Level 2 charging at about 10 to 20 miles of range per hour, with some higher-output units charging faster. Level 2 can fit more charging inside a limited off-peak window and is often better for long commutes or larger EV batteries.

Level 2 charging is not automatically cheaper per kWh, but it may help you avoid peak hours because the car can finish charging sooner inside the low-price window.

How to Calculate Your Charging Costs With TOU Rates

Use this step-by-step method before you switch plans or change your charger schedule:

1. Find your EV efficiency. Use kWh per 100 miles, not MPGe, for cost math.
2. Estimate monthly miles. Use your commute and weekend driving, or check your odometer history.
3. Convert miles to kWh. Monthly miles ÷ 100 × kWh per 100 miles = estimated battery energy.
4. Add a charging-loss buffer. Add about 10% as a planning estimate unless your charger or vehicle reports wall energy directly.
5. Apply each rate period. Multiply the kWh charged in each window by that window’s cents-per-kWh rate.
6. Compare against your current bill. Include household peak usage if the plan applies to your whole home.

Example: You drive 900 miles per month in an EV rated at 30 kWh per 100 miles. That is 270 kWh before losses. Add 10% for charging losses, and your wall energy is about 297 kWh. At $0.25/kWh, the monthly charging cost is about $74.25. At $0.55/kWh, it is about $163.35.

Challenges With TOU Rates for EV Charging

TOU rates are useful, but they are not perfect for every EV owner.

1. Short off-peak windows: A slow charger may not add enough range before the peak window returns.
2. Evening driving needs: If you arrive home low on battery and need to leave again soon, you may have to charge during peak hours.
3. Whole-home peak usage: Air conditioning, cooking, laundry, or electric heating during peak hours can offset EV savings.
4. Seasonal rate changes: A schedule that works in winter may not be cheapest in summer.
5. App or charger settings: A wrong time zone, daylight saving issue, or missed departure setting can cause the charger to run at the wrong time.
6. Renters and multifamily homes: You may not control the charger, meter, or rate plan.

What Next Steps Should You Take for TOU Implementation?

Follow this checklist before enrolling in a new TOU plan:

1. Download recent bills. Review at least three months of usage. A full year is better if you use heavy summer cooling or winter heating.
2. Find your hourly usage. Many utilities show hourly or daily usage in your account portal.
3. Check your utility’s EV plans. Compare whole-home TOU, EV-specific TOU, and separate-meter EV options if available.
4. Calculate EV-only cost. Use your kWh per 100 miles and monthly mileage.
5. Calculate whole-home impact. Include your peak-hour home usage if the plan changes your entire bill.
6. Set charger scheduling. Use your vehicle app, charger app, or utility program.
7. Verify after the first week. Check that charging actually happened during the lower-price window.

If your first month does not show savings, review whether the car charged during peak hours, whether your home peak usage increased, or whether the rate plan has fixed charges that reduce the benefit.

Troubleshooting TOU EV Charging Problems

My Car Started Charging During Peak Hours

Check whether the vehicle or the charger controls the schedule. If both have schedules, they may conflict. Use one main schedule and confirm the time zone in the app.

My Car Was Not Ready by Morning

Your charger may be too slow for the off-peak window. Lower your daily target only if your range needs allow it, start charging earlier if the rate is still affordable, or consider a properly installed Level 2 charger.

My Bill Went Up After Switching to TOU

Look at whole-home peak usage. If air conditioning, cooking, laundry, or electric heat runs during peak hours, those costs may outweigh cheaper EV charging.

My Utility Changed the Rate Window

Update your vehicle and charger schedules. Some plans change by season, and some utilities revise rates after regulatory approval.

Frequently Asked Questions

How is EV charging time calculated?

EV charging time is based on how much energy the battery needs and how much power the charger can deliver. A simple estimate is: needed kWh ÷ charger kW = hours. Real charging can take longer because charging slows near full battery, and some energy is lost during charging.

What is the cheapest time to charge my EV?

The cheapest time is the lowest-price window on your own utility rate plan. It may be overnight, midday, weekends, or a super-off-peak period. Check your rate schedule and then set your vehicle or charger app to charge inside that window.

What is the 80/20 rule for EV charging?

In EV ownership, the 80/20 rule usually refers to keeping the battery between about 20% and 80% for routine daily use when your vehicle maker recommends it. It is a battery-care habit, not a TOU billing rule. For TOU savings, focus on when charging happens and how many kWh you use.

What drains an EV battery the most?

High speeds, hard acceleration, cabin heating, air conditioning, cold weather, roof racks, heavy loads, and steep climbs can increase energy use. Better route planning, moderate speeds, preconditioning while plugged in, and proper tire pressure can help improve efficiency.

Does a TOU plan always save EV owners money?

No. A TOU plan works best when you can move most charging and other high-energy tasks away from peak hours. If your home uses a lot of power during peak periods, or if you often need evening charging, the savings may be smaller.

Can I use Level 1 charging with TOU rates?

Yes, if your daily mileage is low and your off-peak window is long enough. Level 1 is slower, so it may not finish charging before peak rates return. Level 2 charging can be better when you need more range inside a shorter low-price window.

Conclusion

Time-of-use rates can make EV charging cheaper, but they are not a one-size-fits-all solution. Start with your own utility schedule, your EV’s kWh per 100 miles, and your monthly driving. Then compare off-peak and peak costs before switching plans. If the math works, a smart charging schedule can help you plug in normally while your EV waits for the lowest-price hours.

Sources

1. U.S. Department of Energy Alternative Fuels Data Center: Charging Electric Vehicles at Home — backs home charging basics, cost calculation factors, and utility TOU incentives.
2. ENERGY STAR: Electric Vehicle Chargers — backs Level 1 and Level 2 charging rates, smart charger features, safety certification, and efficiency notes.
3. FuelEconomy.gov: All-Electric Vehicles — backs EV efficiency, kWh use, charging efficiency, and general EV performance information.
4. PG&E: Electric Vehicle Rate Plans — example of current EV TOU plan windows and rate-plan structure.
5. Southern California Edison: Electric Vehicle Rate Plan — example of EV TOU charging windows and seasonal rates.
6. San Diego Gas & Electric: Pricing Plans — example of EV and electric-home TOU plans with peak, off-peak, and super-off-peak windows.