With a dynamic energy contract, the price per kWh follows the wholesale price on the energy market. It changes from hour to hour, and on some contracts every quarter of an hour. If you have your own charge point, you can use that: the car sits parked for hours anyway and does not need to charge at a fixed time.
How does it work?
The price is low when supply is plentiful, for example on windy nights or sunny afternoons. It climbs when demand is high, such as on cold winter evenings. You pay the rate of the moment you draw the electricity.
Only the energy part of the bill follows the market. Network costs, taxes and your supplier’s fixed fee come on top. How big those parts are and how they are calculated differs per contract and changes over time. Always ask for the full price formula.
A worked example
Say you drive 1,000 km a month in a car that uses 18 kWh per 100 km. That is 10 x 18 = 180 kWh, before charging losses. Assume the energy part costs 0.10 euro per kWh on average at night and 0.30 euro in the busy evening hours. These are assumptions to calculate with, not real tariffs.
- Everything in the expensive hours: 180 x 0.30 = 54 euro.
- Everything in the cheap hours: 180 x 0.10 = 18 euro.
- Half and half: 180 x 0.20 = 36 euro.
So there is 36 euro a month between the two extremes. In reality that gap shifts with the season and the day, and you still have to compare it with what a fixed contract would cost you. Calculate with your own consumption and the prices in your quote.
Does a charging session fit in the cheap window? A car adding 30 kWh needs a little over four hours at 7.4 kW (30 divided by 7.4 is about 4.05) and nearly three hours at 11 kW. Charging losses come on top, so allow some extra time.
Take someone who gets home at 6 pm and leaves at 7 am. That is 13 hours for a four-hour session, so there is plenty of room to pick exactly the cheapest hours.
What do you need to sort out?
- Check your meter. A dynamic contract needs a digital meter that records consumption every quarter of an hour. If you do not have one yet, ask your network operator about the procedure.
- Compare contracts. Look at the price formula, the fixed monthly costs and the cancellation terms. Also ask how early you know the prices for the next day.
- Set up the schedule. You can do this in your car’s app or your wallbox’s app. Some smart wallboxes and energy apps read the hourly prices themselves and charge in the cheapest hours.
- Enter your departure time. Tell the car or wallbox when you need to leave and how full the battery should be. The schedule then picks the cheapest hours before you go.
- Check after the first month. Look at your bill to see what you paid per kWh and compare it with what a fixed contract would have cost.
Common mistakes
The biggest mistake is looking only at the energy price. The cheapest hour may be the same moment your heat pump or tumble dryer is running. Your quarter-hour peak then rises, and so does your capacity tariff, which can eat the saving. Let your wallbox cut its charging power when the rest of the house draws a lot, or choose a lower power. You can read more in our article on home charging.
A second mistake: charging the car to full every day when you only drive 20 km. Charge what you need, and do it in the cheap hours.
A third: setting the schedule and never checking it again. After a software update or with a new car, the setting sometimes goes back to default. After an update, check that your schedule is still there.
When does it not pay off?
- You mostly charge on the road or at work. The price at that charge point then decides your costs, and your home contract matters little.
- You cannot charge at home at night, for example because you park on the street. You can read more about that situation in charging without a driveway.
- Your consumption is low. With few kWh a month, the saving quickly disappears against the fixed costs.
- You want to know in advance what you will pay. A dynamic contract can turn out expensive in cold, still weeks, and you have little control over that.
If you have solar panels, you would rather charge in the daytime with your own electricity. What you feed back into the grid is paid differently from what you draw, so calculate that combination separately. How to approach it is covered in charging with solar panels.
Estimate your charging costs with the charging calculator and set quotes from several suppliers against your own consumption. Prices and terms change regularly, so go by the supplier’s current figures.