Night-rate EV charging means scheduling your car to draw electricity during a cheaper period on your electricity plan. To make it work, match three things: the supplier's exact time window, the electricity your car needs, and the charging schedule that controls the session.
A two-hour cheap period can be enough for a daily top-up. It will not necessarily refill a large battery in one night. The calculations below show the difference without assuming a particular supplier is cheapest.
Night rates and EV boost periods are different
A conventional day/night plan prices electricity in two bands. Some smart EV plans add a shorter, cheaper boost period; others use a charging rate and a rate for the remaining hours. Do not assume the whole night has the advertised EV price.
For example, Electric Ireland's Home Electric+ Night Boost lists a 02:00–04:00 boost within a 23:00–08:00 night period. Energia EV Smart Drive lists a 02:00–06:00 charging window. These supplier pages were checked on 29 September 2026; confirm your own contract's times and prices.
Use our EV electricity-plan comparison guide to compare windows and whole-house bills. A legacy day/night plan may still suit some households; switching to a smart plan is not automatically a saving.
How much energy fits inside the window?
Energy in kWh = charging power in kW × hours. At a steady 7.4 kW, the arithmetic is:
| Charging window | Electricity drawn at 7.4 kW | Battery energy if efficiency is 90% |
|---|---|---|
| 2 hours | 14.8 kWh | 13.3 kWh |
| 3 hours | 22.2 kWh | 20.0 kWh |
| 4 hours | 29.6 kWh | 26.6 kWh |
The 90% figure is an illustrative assumption, not a measured result for your car. At 16 kWh of battery energy per 100 km, that corresponds to about 17.78 kWh drawn from the supply per 100 km; at an example 10c/kWh, about €1.78 per 100 km. Charging losses vary. The table also assumes your vehicle accepts 7.4 kW and charging is not reduced by load management, temperature or other limits. Measure actual sessions to refine the estimate.
Worked example: topping up a 60 kWh battery
Going from 20% to 80% in a battery with 60 kWh usable capacity adds 36 kWh to the battery. At an assumed 90% charging efficiency, that needs 40 kWh from the electricity supply.
- Battery energy: 60 × (0.80 − 0.20) = 36 kWh.
- Metered electricity: 36 ÷ 0.90 = 40 kWh.
- At a constant 7.4 kW: 40 ÷ 7.4 = about 5.4 hours.
A four-hour window cannot complete that example session entirely at the boost rate in one night. You could top up across more than one night or allow some charging at the next rate, depending on when you need the car.
| Illustrative electricity price | Cost of 40 kWh |
|---|---|
| 10c/kWh | €4 |
| 20c/kWh | €8 |
| 30c/kWh | €12 |
These prices are calculation examples, not supplier quotes. If a session crosses tariff bands, multiply the electricity used in each band by its own rate and add the results. See the home-charging cost guide for annual and per-100km examples.
Set up scheduled charging without competing timers
- Confirm the tariff is active. Use the agreed supply start date and current bill or supplier account. A smart meter on the wall does not by itself confirm an EV plan is active.
- Choose which system controls the session. Follow your vehicle and charger instructions. A car timer and a charger timer can prevent charging if their permitted times do not overlap.
- Enter the correct window and departure needs. Check local time settings and any supplier instructions about seasonal clock changes. Do not copy another customer's schedule.
- Set a charge target suitable for your vehicle. Follow the manufacturer's battery guidance and allow enough energy for your next journey.
- Check the first sessions. Review charger history and supplier consumption data. Confirm that charging actually occurred in the intended hours.
Use the scheduled-charging guide and your charger's product and owner information for the controls on your model.
What if the house cannot supply full power overnight?
An EV charger shares the home's available electrical capacity with other equipment. Load management may reduce charging while another large load runs. ESB Networks advises assessing the combined demand when deciding whether the existing connection is sufficient.
If you have a heat pump, electric heating, a home battery or two cars, include those in the property assessment. A longer cheap window can help only if the installation can safely deliver the energy. Read how solar charging and dynamic load balancing interact before assuming a fixed nightly output.
Frequently asked questions
Can I plug in before the cheap period starts?
With a correctly configured compatible schedule, you can connect the car beforehand and let the charging controls wait. Confirm that behaviour for your charger and car during the first session.
Do I need to fill the battery every night?
No. Plan around the energy needed for your journeys and the vehicle manufacturer's guidance. A daily top-up is a different calculation from charging an empty battery to full.
Is daytime solar charging free?
Surplus solar can reduce electricity imports, but using it in the car may mean giving up an export payment. Compare that opportunity cost with your overnight rate; the better choice depends on your tariffs and when the car is home.
What if I do not have a home charger yet?
Compare installed charger prices and the standard-installation scope, then start a property assessment. Check the SEAI grant process before committing eligible expenditure.