Connectors and charging speed: AC, DC and CCS explained

AC and DC: two kinds of charging

There are basically two ways to move electricity into your EV, and they are different enough to explain almost everything else. AC stands for alternating current and is the slow, everyday charging you find at home and at destination chargers by shopping centres, workplaces and car parks. Here the converter sits inside the car: the car's onboard charger turns the alternating current into direct current before it reaches the battery, and that onboard charger is what sets the ceiling — typically around 11 kW, though some cars can take 22 kW.

DC stands for direct current and is fast charging. Here the converter sits in the charger itself rather than in the car, so the unit can send direct current straight into the battery and bypass the car's slow onboard charger. That is why a fast charger can deliver many times more power than an AC charger, and why you find them along the motorways and at strategic hubs where people are in a hurry. In short: AC is for when the car sits still for hours, DC is for when you need to get moving quickly.

The connector types in Denmark

In practice you will meet three connector types in Denmark, and thankfully you rarely need to think about them day to day — modern EVs use the same connector for the vast majority of situations. Here are the three you may come across:

• Type 2 is the AC standard in Europe. Every new EV sold in the EU has a Type 2 socket, and it is the connector you use for home charging and all ordinary public AC charging.
• CCS (Combined Charging System, also called Combo) is the DC standard in Europe. It builds on the Type 2 connector with two extra power pins for direct current, and it is the connector type used by the vast majority of Danish fast chargers.
• CHAdeMO is an older Japanese DC standard you still see on some of the first EV models, such as the early Nissan Leaf. It is on its way out: new cars no longer ship with it, and fewer and fewer fast chargers offer the connector.

How fast do you charge?

Charging speed is measured in kilowatts (kW), and the more kW, the faster the battery fills. But the numbers on the charger only tell half the story, because speed is decided by the weakest link. An 11 kW AC charger typically fills a battery in 5–8 hours — perfectly fine overnight or while the car is parked anyway. A 50 kW DC fast charger often takes you from nearly empty to around 80 percent in about an hour, while the most powerful fast chargers at 150–350 kW can manage the same 80 percent in about 20–40 minutes.

The important caveat is that the car's own maximum charging power sets the ceiling, not just the charger's. If you plug into a 350 kW fast charger but your car can only take 100 kW, you charge at 100 kW. The charger's figure is a maximum you only benefit from if the car can keep up — so check your car's specifications when judging how fast you can really charge.

The charging curve and the last 20 percent

Charging does not happen at the same pace all the way through. The battery charges fastest when it is nearly empty, and the speed drops gradually as it fills. Above around 80 percent the car slows charging markedly to protect the battery, and the final few percent can take almost as long as the entire first half. This curve is the reason behind the rule of thumb that a fast charge is measured to 80 percent and not to full.

In practice this means the last 20 percent is expensive in time at a fast charger — you stand there charging slowly for relatively little extra range. That is why it is often smarter to charge to 80 percent and drive on, saving the full charge for the slow AC charging at home or at your destination, where time does not cost the same.

What does it mean for the price?

Speed costs. As a rule, the fastest power tiers are also the most expensive per kWh: slow AC charging typically sits lowest, while the most powerful fast chargers sit highest. It is the same trade-off that recurs throughout charging economics — you pay a premium to get moving quickly. If you have time, the cheapest electricity is usually the slow kind.

That makes connector type and power two of the most important filters when you are looking for a charger. On the map here on the site you can filter both by connector type and by power, so you only see the chargers that suit your car and your need — if you want cheap overnight charging, look for AC; if you are in a hurry on a road trip, filter for the high kW figures. Once you understand the link between speed and price, you can deliberately choose the charging pace the situation calls for.