EV Charging Infrastructure Load Planner
Charger Type
A
Voltage
60%
Diversity Factor
Energy Management System
Diversified Demand53.9 kW / 224.6 A
Total Connected Load77.0 kW
Connected Load (Amps)320.8 A
Diversity Factor Applied70%
Existing Load240.0 A
Total Demand464.6 A
Service Upgrade RequiredYes
Recommended Service600 A
Transformer Impact59.9 kVA
Estimated Infrastructure Cost$12,000.00
NEC 625.42 Compliance Notes
- --NEC 625.42 diversity factor applied: 70%
- --Service upgrade required: existing 400A insufficient for 465A demand
Adding electric-vehicle chargers to a building rarely means simply summing every charger at full power. NEC 625.42 lets you apply a diversity factor because not every charger runs at maximum at the same moment. This planner totals the connected load, applies the code diversity factor (and an optional energy-management reduction), adds your existing building load, and tells you whether a service upgrade is required.
Formula
Itotal = Iexisting + (Pconnected × Dfactor × EMS) → amps
- Pconnected
- Total connected charger load (number of chargers × kW per charger)
- Dfactor
- NEC 625.42 diversity factor based on charger count (or a custom value)
- EMS
- Energy-management factor: 0.75 if an EMS is present, otherwise 1.0
- Iexisting
- Existing building load in amps (service rating × existing-load percent)
- Itotal
- Total demand in amps, compared against the service rating
How it works
- Choose the charger type (Level 1 at 1.4 kW, Level 2 at 7.7 or 19.2 kW, or 50 kW DCFC) and the number of chargers to get the total connected load in kW and amps at your service voltage.
- A diversity factor from NEC 625.42 is selected from the charger count (ranging from 1.0 for a single charger down to 0.40 for very large banks); an energy-management system applies an additional 25% reduction. You can override the factor manually.
- The diversified charger demand is added to the existing load (a percentage of the service rating) to get total demand. If that exceeds the service, the tool flags an upgrade and recommends the next standard service size with 25% headroom.
Worked example
Six 7.7 kW Level 2 chargers on a 400 A, 208 V three-phase service that is already at 50% load, using the NEC default diversity factor and no EMS.
- Connected load: 6 × 7.7 kW = 46.2 kW.
- Diversity factor for 6 chargers (NEC 625.42, ≤8 row): 0.80. Diversified demand: 46.2 × 0.80 = 36.96 kW.
- Convert to amps (three-phase, 208 V): 36,960 ÷ (208 × √3) ≈ 177.69 A.
- Existing load: 400 A × 50% = 200 A. Total demand: 200 + 177.69 = 377.69 A.
Total demand ≈ 377.69 A, below the 400 A service, so no upgrade is required (transformer impact ≈ 41.07 kVA).
Frequently asked questions
- What is a diversity factor and why does NEC 625.42 allow one?
- A diversity factor is the fraction of the total connected charger load expected to draw simultaneously. Because vehicles charge at staggered times and taper as batteries fill, NEC 625.42 permits sizing the service for this realistic peak rather than every charger running flat-out at once.
- How does an energy management system reduce the required service?
- An EMS actively limits aggregate charger current so the combined load never exceeds a set ceiling. NEC 625.42 recognizes this by allowing an additional reduction, modeled here as a 25% factor on top of the diversity factor, often avoiding an expensive service upgrade.
- Why are DCFC chargers usually 480 V three-phase?
- DC fast chargers draw very high power (50 kW and up), which would require impractically large conductors at 208 or 240 V. A 480 V three-phase feed lowers the current for the same power, so the tool warns when a DCFC is placed on a lower-voltage service.
- Is the infrastructure cost estimate a real quote?
- No. It is a rough per-charger planning figure to compare scenarios. Actual installed cost depends heavily on trenching, panel work, utility fees, and local labor, so always obtain contractor and utility quotes before budgeting.