AC vs DC charging: what's the difference?

Your car takes a whole night to recharge in your garage, yet recovers a large share of its range during a coffee break on the motorway. Same vehicle, same battery — and yet charging speeds with nothing in common. The difference comes down neither to the brand of the charge point nor to some hidden setting: it comes down to the nature of the current. Understanding the distinction between AC and DC charging means understanding why a 22 kW charge point is useless for certain vehicles, why nobody installs a rapid charger in their home, and how to size a home installation intelligently.

AC and DC: what really happens between the socket and the battery

An electric car battery stores and delivers direct current (DC). The electricity grid, on the other hand, distributes alternating current (AC) — 230 V single-phase, 400 V three-phase. Between the two, a conversion is therefore unavoidable. The whole difference between the two families of charging comes down to where this conversion takes place.

In AC charging, the charge point delivers the alternating current as is, and it is a component in the vehicle — the onboard charger — that converts it into direct current to feed the battery. In DC charging, the conversion is carried out in the charge point itself, which injects direct current straight into the battery, bypassing the onboard charger. The DC charge point is therefore a far more complex machine: it houses high-power converters, their control electronics and their cooling system.

The onboard charger: conductor of AC charging

In AC, the actual charging power is never the one shown on the charge point: it is always the lowest of the three limits in play — the charge point, the site's electricity contract, and above all the vehicle's onboard charger. The latter varies considerably from one model to another: some vehicles accept only single-phase up to 7.4 kW, others three-phase up to 11 kW or 22 kW.

The practical consequence is immediate: plugging in a vehicle whose onboard charger caps at 7.4 kW to a 22 kW charge point will not make it charge any faster. The charge point will offer 22 kW, the vehicle will draw only 7.4. Before choosing your charge point's power, the first question to ask is therefore not "what does the market offer?" but "what does my vehicle accept?" — the information appears in its technical sheet, on the "AC onboard charger" line.

Why home means AC

At home, AC charging is the obvious choice for reasons that are both technical and practical. Technically, your home is supplied with alternating current, single-phase 230 V in most cases, sometimes three-phase 400 V. A wall-mounted AC charge point connects to it naturally, via a dedicated circuit compliant with the NF C 15-100 standard. A DC charge point, by contrast, would require an infrastructure entirely out of step with residential use.

Practically, the decisive factor is time. Your car spends its nights in the garage: charging has long hours ahead of it. A 7.4 kW charge point easily restores the range used up by daily journeys while you sleep. Powers of 11 kW and 22 kW, in three-phase, make sense when the vehicle accepts them and the needs call for it — high-mileage drivers, several vehicles, fast turnaround. Extreme speed simply has no practical value when the vehicle stays plugged in for eight hours.

Why the motorway means DC

On the road, the logic is reversed: the goal is to minimise the length of the stop. This is the territory of DC charging, known as rapid or ultra-rapid. By injecting direct current straight into the battery, the charge point frees itself from the onboard charger's limit and can deliver powers far higher than anything AC allows.

Two realities are worth knowing. First, the cable on DC charge points is always attached to the charge point — thick, sometimes liquid-cooled, it is not meant to travel in your boot. Second, the power shown is a peak power: the battery accepts its maximum charge only within a given window, generally when it is fairly empty and at the right temperature. As it fills up, the vehicle reduces the power to protect the cells. That is why, on a journey, you rarely recharge all the way to the maximum: the last few per cent are the slowest.

Type 2 and Combo CCS: two connectors for two worlds

This electrical distinction can be read directly on your vehicle's charging flap. The Type 2 socket is the European standard for AC charging: it is the one you use at home, at work and on public charge points, in mode 3. The Combo CCS is the European standard for DC charging: it takes the shape of the Type 2 and adds two dedicated power pins for direct current, for mode 4 charging.

The elegance of the system lies in its compatibility: a single flap handles both uses. The upper part receives the Type 2 connector for AC; the full Combo CCS connector slots into it for DC. You need no adapter at all.

"More power is always better": the myth to dismantle

It is the most common reflex — and the most expensive. At home, over-sizing your charge point often brings nothing: if the vehicle's onboard charger caps below it, the extra power will never be used; if the electricity contract can't keep up, the charge point will have to throttle itself anyway or rely on load shedding. Conversely, a properly sized charge point — often 7.4 kW single-phase — covers almost all daily uses without needlessly burdening the installation.

Another myth: "rapid charging damages the battery". The reality is more nuanced. Modern vehicles manage their charging finely, and occasional DC use on the road poses no particular problem. It is the exclusive, intensive use of rapid charging that places more strain on the battery. The right balance is precisely the one the infrastructure draws out: AC for everyday use, DC for the road.

What this means for sizing your installation

Sizing a residential charge point comes down to aligning four elements: your vehicle's onboard charger (and that of the one that might replace it), your electrical supply (single-phase or three-phase), your contract, and your driving habits. A single-phase household with a vehicle that has a 7.4 kW charger has no reason to aim higher; a three-phase household with an 11 kW-compatible vehicle can find real convenience in it. Dynamic load shedding also makes it possible to install a powerful charge point without over-sizing the contract, by modulating the charge according to the home's consumption.

This is exactly the purpose of the technical study that Volticom carries out free of charge before any quote: an analysis of your electrical panel, your contract and your real needs, then a quote within 48 hours after a complete brief, across France. As a QUALIFELEC IRVE P1·P2·P3 and RGE certified installer, we also help you benefit, depending on your situation, from the reduced VAT rate of 5.5% applicable to homes more than two years old, subject to conditions. To review your project, call 09 55 92 66 32.

Frequently asked questions

Can I install a DC charge point at home?

It is neither relevant nor suited to residential use: a DC charge point requires an electrical infrastructure and an investment out of all proportion to a private individual's needs. AC charging from 7.4 to 22 kW, over the long hours of parking at home, covers everyday use far more simply.

Does a 22 kW charge point recharge three times faster than a 7.4 kW one?

Only if your vehicle's onboard charger accepts 22 kW in three-phase and your installation allows it. Otherwise, it is the onboard charger that sets the actual speed: a 22 kW charge point will not charge a vehicle limited to 7.4 kW in AC any faster.

Do I need to bring my own cable to a rapid charger?

No. DC charge points always have their cable attached, with a Combo CCS connector. Your personal Type 2 cable only concerns AC charging, at home and on public on-street charge points.

Does rapid charging wear out the battery prematurely?

Occasional DC use on a journey poses no problem: vehicles manage their charging to protect the cells. It is the almost exclusive use of rapid charging that places more strain on the battery over time. Charging in AC every day and reserving DC for the road remains the healthiest practice.

How much does installing an AC charge point at home cost?

The price depends on your electrical panel, the cabling distance and the chosen power (7.4, 11 or 22 kW): it is therefore always quoted individually. Volticom draws up a technical study and a free quote within 48 hours after a complete brief, across France, with no commitment, including the ADVENIR scheme (subject to its rules) and subject to eligibility.

Can I install my charge point myself to save money?

No: beyond a simple reinforced socket, fitting a charge point falls under the NF C 15-100 standard and requires a dedicated circuit with a 30 mA Type B residual current device, on pain of danger and loss of insurance cover. The law also reserves installation for QUALIFELEC IRVE qualified professionals, a condition equally necessary to access grants such as ADVENIR.

Why use a QUALIFELEC-qualified IRVE installer rather than a regular electrician?

QUALIFELEC IRVE qualification (P1·P2·P3) attests to specific expertise in charge points: sizing, dynamic load shedding, safety and compliance. At Volticom, it comes with a decennial liability insurance policy with AXA, subject to the declared activities, limits and terms of the current insurance certificate, together with responsive after-sales service — concrete signs of seriousness and peace of mind.

How long does it take to have a charge point fitted?

The fitting itself is generally carried out within a timeframe confirmed after the site assessment, once the technical study has been validated and the charge point chosen. Everything starts with our free quote within 48 hours after a complete brief, across France: you quickly know what to expect, with no nasty surprises or unnecessary delay.

Will a more powerful charge point send my electricity bill or my contract through the roof?

No, because a charge point uses the same amount of energy (in kWh) to recharge your vehicle whatever its maximum power; only the speed changes. To avoid over-sizing your contract, we include load shedding and dynamic management that modulate the charge according to the home's consumption, which our free study costs out precisely.

Does Volticom operate everywhere in France and how do I get a quote?

Yes: from our head office in Paris, we cover the whole of France through a network of certified installer partners, for consistent quality wherever you are. To launch your project, request your free quote within 48 hours, across France on 09 55 92 66 32 or at contact@volticom.fr, with no commitment whatsoever.