The question that I am asked at least three times a week is: Should I use DC or AC fast charging stations for my project? And my answer is always the same: it depends on what your customers do with their cars while they’re at your station. A vague answer, you might say? Not really. Honestly, if you make the wrong choice, you’ll either waste your money on oversized equipment or annoy your customers with slow chargers that don’t meet their needs.
I had one customer in Lyon who had spent a fortune on six 120 kW DC fast charging stations, which he had installed in his hotel parking lot. What a disaster! His customers were parking their cars in his hotel parking lot for one night only, which meant that they did not need fast charging at all. They needed slow charging. He could have installed thirty AC charging stations for the same money and satisfied all his customers. Instead, he had to pay an astronomical electricity bill, and half of his charging stations were never used. Don’t make the same mistake. Let’s analyze this in more detail.
The Basic Difference and Why It Really Matters
What most people don’t bother to explain is that the difference between AC and DC charging is not just about charging time. The difference is really in location. In my opinion, people tend to overcomplicate things. In AC charging, alternating current is simply connected from the charging station to the vehicle. From there, the current is converted to direct current to charge the battery. The limiting factor in charging time is not your charging station, but your vehicle’s onboard charger. In fact, most electric passenger vehicles have onboard vehicle chargers with a maximum power output ranging from 7 kW to 22 kW. So, with a state-of-the-art 22 kW AC charging station, you can only charge your vehicle to the maximum speed that your vehicle is capable of.
For DC charging, direct current is simply injected into the battery, bypassing your vehicle’s onboard charger entirely. That is why DC charging stations have maximum power outputs ranging from 40 kW, 120 kW, to 240 kW.
Charging Speed: The Numbers That Really Matter
I’ll give you real numbers, not promises. A standard EV battery will have a capacity of 60-80 kWh. Let’s use a 75 kWh battery as an example.
- 7 kW AC charger: 10 to 11 hours to full charge, 2.5 hours to add 100 km
- 22 kW AC charger: 3.5 to 4 hours to full charge, 45 minutes to add 100 km
- 60 kW DC charger: 75 to 90 minutes to full charge, 15 minutes to add 100 km
- 120 kW DC charger: 40 to 50 minutes to full charge, 8 minutes to add 100 km
- 240 kW DC charger: 20 to 25 minutes to full charge, 4 minutes to add 100 km
But here’s the catch. These numbers are based on an EV being able to draw that much power. In reality, many private electric vehicles will draw a maximum of 50-150 kW even if the charger can supply more. If you’re in a business of running a fleet of trucks or buses, then a 240 kW or more charger starts to make economic sense because those large batteries will be able to draw that much power.
The Key Question: What Do Your Customers Do?
That’s the only question I ask each customer before making a recommendation. Honestly, it’s the only question that really matters.
Scenario A: Hotel, office building, residential complex. Your customer is parking for at least 4 to 8 hours. Your customer doesn’t care about speed. Your customer just wants their battery fully charged when they wake up or finish work for the day. A 7 kW AC charger is just right for these types of customers. In these types of scenarios, DC fast chargers are not necessary at all. You’d be spending 5 to 8 times more on equipment to solve a problem that doesn’t even exist.
Scenario B: Shopping mall, supermarket, restaurant. The time spent in this scenario is 45 minutes to 2 hours. This is the grey area. A 22 kW AC charger can charge the battery for 30 to 50 km. That is good, but nobody is going to save their life with that. But a 60-120 kW DC fast charger is a different story altogether. A customer comes in with 15 percent battery charge and goes out with 80 percent battery charge after a leisurely lunch. That is a good reason for them to come to your shopping mall instead of the one across the road.
Scenario C: Highway rest area, service station, charging station. In this scenario, time is of the essence. The customer is stopping to charge his or her battery. If your charging station does not have at least 60 kW, you will have queues and frustrated people waiting to charge their cars. The future is 150-350 kW charging points. If you are not at that level, forget about it.
Scenario D: Fleet depot, logistics, delivery, municipality. Fleets are a different ball game altogether. I had to work with a logistics manager in Berlin who thought he needed forty AC charging points for his delivery fleet. We did the math, and he did not have space or the capacity for forty charging points. We changed his forty AC charging points to eight 40 kW DC charging points, and his delivery vans were charged in rotation.
Cost Comparison: Equipment, Installation, Cost of Ownership
Okay, let’s move on to the financial side. AC versus DC is like comparing a bicycle to a truck.
- 7 kW AC: $800 to $2,500
- 22 kW AC: $2,000 to $6,000
- 60 kW DC: $8,000 to $18,000
- 120 kW DC: $18,000 to $35,000
- 240 kW DC: $40,000 to $80,000
If you are offered a 120 kW DC charger for $7,000, run. Either they are lying about their certifications, or their product is junk. Or both.
Installation: AC is a snap — $500 to $2,000 per connection. DC is a nightmare. High voltage, transformer changes. For a 120 kW charger, you might be looking at $15,000 to $50,000 in hidden costs. Yes, you read that right.
Revenue and ROI
AC is a money pit. DC is a money generator. You cannot charge people extra for AC at a hotel because AC is a service, like Wi-Fi. With DC, you charge people for every kilowatt-hour or every minute. A 120 kW charger at $0.35 per kilowatt-hour means you make $28 per hour. In a high-traffic area, you’ll pay for yourself in less than 18 months. You’ll never get that kind of return on investment with a slow AC charger.
Grid Capacity
I see many projects fail at the permitting stage because nobody thought about the grid. A single charger of 120 kW consumes more electricity than an office building. Try to install three without thinking about the grid, and you will blow the local transformer.
The solution is dynamic load management. Our chargers in Hongjiali have this capability. If four cars charge at the same time, the output power is slightly reduced not to exceed the grid capacity.
For enterprises, there is a trend towards a solution that includes solar, solar, and charging: a microgrid. Although costly to implement, it gives you the opportunity to install a fast charging station anywhere you want without waiting for years for permission from the electricity provider.
My Practical Guide
If users stay for more than 3 hours, if your budget is tight, if you don’t plan to make any profit from selling electricity, or if the grid is not reliable, then you should consider a 7-22 kW AC charger.
If users stay for 30 to 90 minutes, if you do plan to make some profit from selling electricity, or if you have a fleet, then you should consider a 40-120 kW DC charger.
If you’re charging on a highway, if you’re building a dedicated charging station, or if you’re charging trucks and buses, then you should consider a 150 kW DC charger or above.
What Hongjiali Offers
We provide AC chargers with capacities of 7 kW to 22 kW. We provide DC fast chargers with capacities of 40 kW to 480 kW. We provide V2G bidirectional chargers. We provide solar charging and storage stations.
If you’re planning a charging station but you’re not sure where to start, send us the details: number of vehicles, average parking time, electrical panel capacity. We’ll do the calculations. No obligation.