No code or standard fixes a charger count for a 100-space car park — the 100 spaces are almost irrelevant to the answer. The count falls out of three numbers you measure yourself: how many EVs are present at your busiest hour, what share of them will plug in, and how many cars each bay can serve during that busy window. The worked example below labels every assumption, so you can run your own figures through the same arithmetic.
Key Takeaways
- There is no chargers-per-space rule: the count comes from peak EVs, plug-in share and turnover — spaces are not an input.
- Connectors = (peak EVs × plug-in share) ÷ cars per bay in the busy window, rounded up.
- Stay length moves the answer as much as EV numbers do; measure it, do not assume it.
- If the supply cannot carry the worksheet’s count, stage the fit on prepared routes rather than shrinking the method.
The Three Inputs (Spaces Are Not One of Them)
| Input | Where it comes from |
|---|---|
| EVs present at the busiest hour | Your own count on peak days. Simultaneous EVs are the binding figure — a daily total hides the peak |
| Plug-in share | The share of those EVs that actually want a charge — some arrive nearly full or stay ten minutes. Err low: overstating it buys idle hardware |
| Cars per bay in the busy window | Window length divided by average charging stay. A bay in a six-hour window serves two 3-hour stays, but only one car that parks all day |
The formula is then simple: connectors needed = (peak EVs × plug-in share) ÷ cars per bay, rounded up. Connectors, not units — one connector charges one car at a time, so a dual-connector station counts as two.
The Worked Example — Every Assumption Labelled
These inputs are invented for illustration — substitute your own counts; the method is the article. Example assumptions: a six-hour busy window; 12 EVs present at the peak hour; two in three plug in, so 8 cars want a bay; the average charging stay is 3 hours, so each bay serves 2 cars across the window. Result: 8 ÷ 2 = 4 connectors — two dual-connector units.
| Change one assumption | Arithmetic | Connectors needed |
|---|---|---|
| Base case, as above | (12 × ⅔) ÷ 2 | 4 |
| Stays last the whole window (workplace-style parking) | (12 × ⅔) ÷ 1 | 8 |
| Quieter site: 6 EVs at peak, half plug in | (6 × ½) ÷ 2 | 2 (1.5 rounded up) |
Notice what moves the answer: stay length and peak EV presence — not the 100 spaces. Two car parks with identical space counts can land on 2 connectors and 8 connectors.
The Power Check That Can Stage the Answer
The count is also an electrical claim. Your licensed electrician’s load summary tests the total — every circuit sized at 125% of charger current under the NEC continuous-load rule — against the site’s confirmed capacity. If the supply carries fewer connectors than the worksheet asks for, the answer is staging, not a smaller worksheet: fit what the supply supports, on routes prepared for the full count. DOE-cited U.S. figures put public Level 2 at about $3,500 equipment plus $2,500 installation per connector, so staging is a real sum either way — our commercial installation cost guide shows where it goes, and our workplace charging program guide covers the staff-parking case.
Hardware in Units of Two Connectors
Once the worksheet gives a connector count, hardware divides by connectors per unit. The EV-AC03201T dual-connector AC station serves two bays per unit — two Type 2 connectors sharing up to 43 kW (22 kW per connector), OCPP 1.6J, RFID, IP54 — so the base case above is two units on two supply points. For wall-mounted structured bays, the EV-ACT3204PE 22 kW wallbox (three-phase, tethered Type 2 cable, RFID and app, IP66, CE) adds one connector per unit. See the commercial EV charging range for both.
Frequently Asked Questions
Is there a rule like one charger per ten spaces?
There is no general rule of that kind, and this worksheet deliberately produces none. Some local codes set requirements for new construction in their own terms — a question for your local authority and design team, answered from your jurisdiction’s current text, not from a ratio in an article.
Does a 100-space car park mean 100 cars a day?
No — spaces turn over. A retail space may hold several cars a day; a staff space holds one. That turnover is exactly why spaces are not an input: the same 100 spaces can carry very different EV demand.
Should we prepare for more chargers than we fit now?
Yes — capacity, ducting and bay preparation are cheapest while the ground is open once. Fit connectors against counted demand; prepare routes for the count your records may argue for later.
Related Reading
- How to Plan a Workplace EV Charging Program
- How Much Does It Cost to Install a Commercial EV Charging Station?
- How Do Commercial EV Charging Stations Work?
- Where to Install an EV Charging Station: Site Selection Guide
