Charging Station Load Calculator
This calculator estimates the total electrical load a mixed EV charging site places on its service -- across Level 1, Level 2, and DC fast chargers -- and applies a simultaneity/diversity factor to estimate realistic peak demand. Multiply each charger type's count by its typical power rating, sum the connected loads, then scale by the share of capacity actually drawn at once. For a deeper dive into DC fast charger stall count and utilization specifically, see the DC Fast Charger Sizing Calculator; once you know your site peak demand, the Transformer/Substation Sizing Calculator helps size the upstream electrical infrastructure.
Standard 120V outlets, roughly 1.4 kW each -- rarely used for commercial sites but included for completeness.
Typical Level 2 chargers run about 7.2 kW each.
The percentage of total connected charger capacity actually drawn at once during peak usage. Mixed-use sites often run lower simultaneity than DCFC-only sites since Level 2 sessions are longer and less concentrated.
Level 1 chargers × 1.4 kW
Level 2 chargers × 7.2 kW
DC fast chargers × power rating
Level 1 + Level 2 + DC fast
total connected load × simultaneity factor
Results update live as you type. For planning and field-check estimates — always verify against applicable standards and equipment ratings.
How we calculate this →Mixed-use charging sites hide an important asymmetry: two DC fast chargers alone (300 kW) can dwarf ten Level 2 chargers combined (72 kW) in connected load, even though the DCFC stalls serve far fewer vehicles per hour of dwell time. When sizing site electrical service, don't just count chargers -- weight them by power rating. A 50% simultaneity factor is a common planning assumption, but real utilization depends heavily on your specific traffic pattern and should be validated against actual usage data once the site is operating.
How charging station load is calculated
Sizing the electrical service for an EV charging site starts from the connected load of every charger on the property, then applies a simultaneity (diversity) factor to estimate the peak demand the service actually has to deliver. Five quantities tie the calculation together.
Total Connected Load - Level 1 (kW) = Number of Level 1 Chargers × 1.4 kW, using the SAE J1772 standard rating for a 120V Level 1 outlet. Total Connected Load - Level 2 (kW) = Number of Level 2 Chargers × 7.2 kW, the typical 240V Level 2 rating common to workplace and destination charging. Total Connected Load - DC Fast Chargers (kW) = Number of DC Fast Chargers × DC Fast Charger Power Rating (kW), where the power rating reflects the specific DCFC units installed (commonly 50-350+ kW from Tesla Supercharger, Electrify America, EVgo, and others). Total Connected Load (kW) = Level 1 + Level 2 + DC fast connected loads; at the defaults (0 L1, 10 L2 at 7.2 kW, 2 DCFC at 150 kW), that is 0 + 72 + 300 = 372 kW.
Site Peak Electrical Demand (kW) = Total Connected Load × (Simultaneity/Diversity Factor ÷ 100). The simultaneity factor is the percentage of total connected capacity actually drawn at the same moment during peak usage -- not every charger runs at full power simultaneously. At 50%, the 372 kW connected load becomes a 186 kW peak demand, which is what the site's transformer, feeder, and service panel must be sized to deliver. Sites with mostly DC fast chargers often run higher simultaneity (60%+) since sessions are short and concentrated, while mixed sites with many Level 2 chargers (longer, more staggered sessions) often run lower, around 40-50%. Two practical notes: utilities and interconnection studies care about peak coincident demand, not average draw, so size service requests from peak; and the simultaneity factor is a planning assumption that should be validated against real usage data once the site is operating. Data sources: SAE J1772 standard (Level 1/2 power ratings); DCFC charger manufacturer specifications (Tesla Supercharger, Electrify America, EVgo, others); EV charging infrastructure planning guides from DOE and NREL; utility interconnection studies on EV charging load diversity.