AC Chargers vs DC Chargers

(Joseph Gottlieb, CTO, Tuesday June 15, 2021)

There are two basic types of chargers: AC chargers and DC chargers (also known as fast chargers). Before you jump to the conclusion that DC fast chargers are always the better choice, wait a second – both types of chargers have their place. In particular, AC chargers (especially Type 2 AC chargers, which run off of 240VAC power with a maximum output of up to roughly 19kW) are great for residential and workplace applications, where there is a significant amount of time to charge the electric vehicle. To put this in context, the average US home daily energy consumption is 28.9kWh. A 19kW charger running for 1-1/2 hours will roughly double the energy consumption of this average US home, but it’s power demands are compatible with those of most US homes. In comparison, DC fast chargers are typically supplied by 480VAC three-phase power. Few homes (if any) have this type of power, and the power consumed by even a small DC fast charger can be 60kW or more – such a charger would consume 2X the power of an average US house in a single hour.

The value of DC fast chargers for the average auto is in two use cases: i) the “filling station” scenario, where you want to put as much power as possible into a vehicle as quickly as possible; and ii) retail scenarios, where a car is parked for an hour or less, and the “circulation” cars through spaces with the DC chargers is high. In both of these use cases, the cost of the DC fast charger can be spread across a large number of quick charging sessions. In both of these scenarios, an AC charger (even a Level 2 charger) will only be able to charge an EV to a small percentage of its total capacity in the time of an hour (or less). The other place that DC fast chargers fit in is for the charging of medium- and heavy-duty vehicles. These vehicles have battery capacities of 1.5X to 6X the capacity of most light-duty (auto/SUV) EVs. Even with a DC fast charger, it can take hours to recharge these vehicles to capacity.

So as new federal grant programs look to expand the number of EV charging stations, making the bulk of these DC fast chargers makes a lot of sense. And if you are looking for made in the USA high-power DC fast charging systems for those EVs, look to Rhombus Energy Solutions. Our market-leading bi-directional EV charging systems (which are designed from the start for the needs of fleet operators) are designed and built in the USA. Rhombus also excels in the design of high-power smart inverters for next-generation renewable energy and energy storage deployments. Our expertise in energy management system (EMS) software is also embedded in our VectorStat EMS controller and software which is embedded in our EV charging systems and smart inverters. We have built over a thousand V2G-capable high-power, high-reliability chargers and bi-directional smart inverters for a variety of different sizes and classes of EVs. Find out how we can help you by contacting us at, or by reading our Vehicle to Grid Solution Brief.