Time-of-Use Rates & Overnight EV Charging

An electric car is close to the perfect time-of-use customer. It needs a large amount of electricity, it needs it regularly, and — crucially — it does not care whenit gets it, as long as the car is full by morning. Almost nothing else in your house has that property. That combination is why the single biggest lever on what home charging costs you is usually not the charger, the car or even the efficiency — it is the hour you buy the electricity in.

Why time-of-use rates exist

Electricity is not equally expensive to produce at all hours, and the EIA is straightforward about this: the cost to supply electricity changes minute by minute, prices are usually highest in summer when total demand is high and more expensive generation is brought online, and demand — and therefore cost — is highest in the afternoon and early evening.

Most customers never see that. As the EIA puts it, most consumers pay prices based on the seasonal average cost of providing electricity, so they don’t experience the daily fluctuations. A time-of-use tariff is the option to see them instead: some utilities offer time-of-day pricing specifically to encourage conservation and reduce peak demand. You pay more during the expensive hours and less during the cheap ones.

For context on the baseline, the EIA reports that residential electricity averaged 17.30 cents per kWh in 2025. That is a national average across a country where rates vary enormously by state and utility, so treat it as an anchor rather than your number — yours is on your bill.

What a TOU tariff typically looks like

Structures vary by utility, but most share the same shape:

• Peak— the expensive window, usually late afternoon into evening on weekdays, when everyone comes home and turns things on.
• Off-peak— the cheap window, typically overnight, often starting somewhere around 9pm to midnight and running to early morning.
• Mid-peak or shoulder— an in-between band that some tariffs include.
• Seasonal variation— summer peak periods are frequently longer and more expensive, which follows directly from summer being when demand peaks.
• Weekend and holiday differences— many tariffs treat these as off-peak all day.

Some utilities also offer a dedicated EV rate, sometimes on a separate meter for the charger circuit. That can be attractive because it isolates the car from the rest of your household’s consumption — but it usually involves a metering installation, so weigh that cost against the saving. Your utility’s tariff sheet is the authority for all of this, and it is a genuinely worthwhile twenty minutes.

Working out what it’s worth to you

There is no national answer here, because peak-to-off-peak spreads differ several-fold between utilities. But the arithmetic is simple and you can do it with your own numbers.

Step one: how many kilowatt-hours does your driving need?Take your monthly mileage and divide by your car’s real efficiency in miles per kWh. A car doing 3.5 miles per kWh driven 1,000 miles a month needs roughly 286 kWh. Add a little for charging losses — the DOE and EPA note that AC charging losses are accounted for in the EPA label figures, and the energy that leaves your meter is always slightly more than what reaches the battery.

Step two: price those kilowatt-hours twice.Once at your utility’s peak rate, once at its off-peak rate. The difference is what scheduling is worth per month, before you change anything else about your household.

Step three: check the rest of the house. This is the step people skip and then regret. A TOU tariff makes allyour peak-hour consumption more expensive, not just the car’s — cooking, air conditioning, laundry, the dishwasher. If your household is home and active from 4pm to 9pm every day, the car’s saving may be partly eaten by everything else. Most utilities will run a comparison against your last twelve months of actual usage; ask them to.

Run it once at your peak rate and once at your off-peak rate. The gap between the two numbers is the whole argument on this page.

How to actually schedule it

Two places can hold the schedule, and it is worth understanding why we usually recommend the car.

From the car (recommended for most people).Nearly every modern EV lets you set a departure time, a charge limit and a scheduled start in the vehicle’s own app or dashboard. Two advantages over the charger: it knows the state of charge, so it can decide how long it actually needs; and the schedule follows the car everywhere, including a relative’s house or a workplace charger. Setting a departure time rather than a start time is the better pattern in winter too, because it lets the car finish close to when you leave and preheat on shore power.

From the charger.A smart charger schedules the circuit rather than the car, which matters if you have two vehicles sharing one unit, if you need to meter or bill the charging separately, or if your car’s scheduler is unreliable. It also gives you per-session energy and cost data, which is how an abstract tariff becomes a number you can check. Our best smart chargers covers the field, and smart vs dumb chargers works through whether you need one at all.

A practical warning about doing both: if the car and the charger each hold a schedule, they can conflict — the classic failure is a car that waits for its window while the charger has already closed the circuit, and you wake up to an empty battery. Pick one place for the schedule and leave the other permanently open.

Getting the most out of an off-peak window

• Check the window is long enough.At 40 amps you add roughly 34 miles of range per hour; at 48 amps about 40. A six-hour off-peak window at 40 amps is about 200 miles of range — ample for nearly everyone. If your window is short and your mileage is high, that is one of the few genuinely good arguments for 48 amps.
• Set a charge limit, not just a schedule.Follow your manufacturer’s daily charge-limit guidance for your specific car; cheap electricity is not a reason to override it.
• Move the other big loads too. Dishwasher and laundry overnight compound the saving on a TOU tariff, and cost nothing to shift.
• Look for ENERGY STAR on the charger.Certified chargers use about 40% less energy in standby than non-certified ones — a small, permanent saving that applies at every hour of the day.
• Re-check after a tariff change. Utilities revise TOU windows and rates. A schedule set two years ago may now start an hour before the cheap window does.

The bigger picture

Even without a TOU rate, charging at home is typically far cheaper per mile than public fast charging or gasoline — the comparison we work through in EV charging vs gas. A time-of-use tariff is a second, independent saving stacked on top: same car, same charger, same kilowatt-hours, bought at a different hour.

It is also the one saving that requires no hardware. Before you spend money on a faster charger or a smarter one, spend twenty minutes on your utility’s tariff page and your car’s charging schedule. That is frequently the highest-return twenty minutes in the whole process. When you are ready to price the rest, our installation cost guide and incentives guide cover the one-off side of the ledger.