When faced with buying an electric car or planning the installation of charging infrastructure, we quickly encounter two concepts: AC and DC. Although both abbreviations mean replenishing energy in the battery, the technology behind them differs fundamentally. Understanding these differences is crucial so as not to overpay for equipment that will not meet our expectations, or to block office work due to charging that is too slow.
What is the difference between alternating current and direct current, and which solution will work well at home, in a company, and on a long route?
AC vs. DC: Where is the main difference?
Simply put, the difference lies in where the current conversion takes place from alternating current (flowing from the grid) to direct current (required by the car battery).
- AC charging (alternating current, e.g., home wallboxes): Current from the grid goes to the on-board charger in the car, which converts it into direct current used to charge the battery. Because the power of the car’s on-board charger is limited (usually to 11 kW or 22 kW), this process takes longer.
- DC charging (direct current, so-called “fast stations”): Current conversion takes place inside the charging station itself, which is a powerful appliance the size of a wardrobe. The station sends direct current directly to the car’s battery, bypassing the car’s limitations. As a result, power can range from 50 kW to even 300 kW and more.
What to choose for the home and housing association?
In home conditions and multi-family housing, AC stations (wallboxes) with a power of 11 kW are unbeatable.
Why? Home electrical installations rarely allow for more without expensive connection upgrades. Moreover, the car remains parked all night (often 8–10 hours), which at 11 kW is entirely sufficient to fully charge almost any battery from zero to one hundred percent.
- Costs and requirements: Purchasing a good wallbox is an expense of several thousand PLN. It requires a three-phase connection, appropriate protections, and in the case of housing associations Dynamic Load Balancing so that charging a car does not cut off power in the entire residential vertical stack.
What to choose for a company?
The choice for enterprises depends on the fleet’s activity profile and who will use the chargers:
- Employee parking (AC): If employees leave cars for 8 hours while working, smart AC wallboxes (11 kW / 22 kW) are completely sufficient. They are cheaper to purchase, put less strain on the grid, and allow for a calm replenishment of energy during the day.
- Delivery vans in continuous motion / customer visits (DC): If a company employs couriers or sales representatives whose cars must hit the road after an hour of stopping, or if it wants to offer fast charging to guests, a smaller DC station (e.g., 30–50 kW power) is necessary. However, one must expect a much higher equipment cost and the requirement of having a strong power connection.
What to choose on the road?
During long trips, time is crucial. No one wants to stand by a hotel or gas station for 6 hours.
Roadside charging hubs consist almost exclusively of powerful DC chargers. They allow you to top up the car from 10% to 80% in 20–40 minutes (depending on the maximum power accepted by a given car model). This is the ideal moment to grab a coffee and stretch your legs.
In summary, the choice between AC and DC technology depends primarily on the time you have and your infrastructure capabilities.
AC stations (wallboxes) with 11 kW power are an economic foundation for the home, housing association, and companies where cars remain parked for many hours. They work slower because they use the car’s on-board charger, but they are cheaper to buy and safe for the home network.
In turn, DC stations are powerful devices created for fast travel and intensive commercial fleets. By bypassing the car’s limitations and transferring direct current directly to the battery, they allow energy to be replenished in a dozen or several dozen minutes, although they require powerful connections and a significantly larger investment budget.