A 22 kW Level 2 charger at a hotel beats a 50 kW DC fast at the same site — and the math isn't even close. How to size against vehicle dwell time, not headline output.
Most charger sizing conversations start in the wrong place. Buyers ask “what's the fastest charger I can get?” when the question they should be asking is “how long are vehicles parked at this site, and what energy do they actually need?” Get the dwell time right and the kW answer falls out of it.
Here's the framework we use with every site that walks in the door, with the math worked.
Every dollar spent on charging speed above what the dwell time can absorb is a wasted dollar. A 150 kW DC fast charger at a hotel where guests stay 14 hours overnight delivers exactly the same energy as a 7.7 kW Level 2 charger over the same period — about 100 kWh, which is a full charge for almost any EV on the market. The DC fast charger costs 8 to 12 times as much, draws far more service capacity, requires a far more expensive utility connection, and ends up sitting idle for most of those 14 hours because the vehicle finishes early.
The framework: match dispenser power to the energy the vehicle needs divided by the time the vehicle is there. Anything faster than that is overcapacity you're paying for and underutilizing.
The arithmetic is straightforward. To deliver E kWh of energy in T hours, you need at least E/T kW of charger power. With a roughly 90% charging efficiency factor, the practical sizing rule is:
Required charger kW = (Energy needed in kWh) / (Dwell time in hours) / 0.9
Run that for a few common scenarios:
| Site type | Typical dwell | Energy per session | Required power | Right-sized charger |
|---|---|---|---|---|
| Hotel overnight | 10–14 hrs | 40–80 kWh | 3–9 kW | Level 2 (7.7 kW) |
| Workplace daytime | 6–9 hrs | 20–40 kWh | 3–7 kW | Level 2 (7.7 kW) |
| Mall / shopping | 2–4 hrs | 10–25 kWh | 3–14 kW | Level 2 (11–19.2 kW) |
| Restaurant / dinner | 1–2 hrs | 10–20 kWh | 6–22 kW | Level 2 (19.2 kW) or low DC |
| Highway corridor | 20–40 min | 30–60 kWh | 50–180 kW | DC fast (50–180 kW) |
| Fleet quick-turn | 15–30 min | 40–80 kWh | 100–320 kW | DC fast (180–360 kW) |
The pattern is unambiguous. Most non-corridor sites are Level 2 sites. The exceptions are exactly the cases where dwell time is short and energy demand is high — corridor stops, fleet quick-turn depots, and a narrow band of urban use cases.
Here's where the math gets stark. A typical project budget per port, including hardware, installation, and permits:
(Ranges vary widely by region, utility, and site complexity. These are ballpark for a typical US commercial site without major utility upgrade work.)
For a hotel with 20 parking spaces and overnight dwell times: 20 Level 2 ports at $4,000 each = $80,000 total. Two DC fast ports at $80,000 each = $160,000 for one-tenth the simultaneous coverage. The Level 2 build serves 20 guests at once with no waiting; the DC fast build serves 2 at a time and creates queue dynamics that hotels generally find unacceptable.
Three scenarios where the math flips:
The dwell time is 20 to 40 minutes and the driver expects to be back on the road. Level 2 cannot deliver enough energy in that window. DC fast (typically 150 kW or higher) is the only option.
Vehicles need to be back in service within 30 minutes between routes. Same logic as corridor stops: dwell is short, energy demand is high, only DC fast works.
Drivers paying a premium for fast top-ups during a 30-minute coffee or shopping stop. The economics depend on session pricing supporting the higher capex.
Many sites benefit from a mix. A hotel with 50 spaces might do 40 Level 2 ports for guests and 2 DC fast ports for through-travelers who aren't staying. A fleet depot might do 20 Level 2 ports for overnight charging and 2 DC fast ports for emergency turn-arounds. The mix-ratio is set by the utilization profile, not by the headline kW.
This framework assumes typical battery sizes (60–100 kWh) and typical charging behavior (drivers don't deplete to zero). As fleet vehicles trend toward larger batteries and as drivers continue to charge opportunistically rather than to empty, the dwell-time logic gets stronger, not weaker. A vehicle with a 120 kWh battery doesn't need DC fast charging at a workplace any more than a vehicle with a 60 kWh battery does — arguably less, because the reserve buffer is larger.
Size for the dwell time you have, not the kW your vendor wants to sell you. If you're not sure which side of the line your site falls on, our product team will walk through your specific case — no charge for a sizing review.
Send your site type, parking count, and expected utilization. We'll size the build — mix of L2 and DC fast, port count, service requirement — before you commit to anything.