There is no universal best setup for a 20-unit building — there is a sequence that finds yours. Count the households that actually drive EVs, have the building’s spare capacity confirmed by a licensed electrician, start with a small shared pool of Level 2 chargers under access control, and run the cable routes and capacity for the expansion at the same time. The worked example below shows the sequence end to end.
Key Takeaways
- Sequence first: survey the EV households, confirm capacity in writing, then choose the layout.
- Overnight dwell makes Level 2 pace ample; the binding constraint is cars charging at once, not speed.
- A shared pool under access control is usually the right stage one at 20 units; prepare conduit and capacity for more.
- Every example number here is invented — your survey count is the only figure that should size the install.
Step 1 and 2: Count Drivers, Then Capacity
- Survey the building, not the market. List the households with an EV today and those who say they will buy one within the lease or ownership horizon. In a 20-unit building that list is short enough to be exact — it, not a national adoption figure, sets the first charger count.
- Confirm capacity in writing. A licensed electrician checks the service and panel for spare capacity. Charging is a continuous load under the NEC, so each circuit is sized at 125% of the charger’s current: a 32 A charger sits on a 40 A circuit, a 48 A charger on a 60 A circuit.
- Match power to the dwell. Residents park overnight, and Level 2 at 7–19 kW (U.S. DOT) adds roughly 10–20 miles of range per hour — overnight refills a daily commute many times over. Speed is not the constraint in a residential garage; simultaneous cars are.
Our guide to load calculation basics for buildings walks through how the capacity check is done.
Step 3: Choose the Layout
| Layout | How it works | Fit at 20 units |
|---|---|---|
| Shared pool | A few chargers in common bays; any resident with access can use them, sessions recorded per user | Usually the right start — the chargers work every night instead of sitting at one household’s space |
| Assigned per household | A charger at each EV household’s own space | Clean cost attribution, but chargers idle when that household travels, and every new EV means a new install |
| Hybrid | A shared pool now, with capacity and conduit prepared so assigned units can be added | The phased answer — pool first, assignment later where demand proves permanent |
Worked example — all figures invented for illustration. Say the survey finds 5 EV households today and 3 more likely within two years, in a building with 20 spaces. A defensible stage one: two dual-connector stations giving 4 shared bays, RFID access so each session is recorded to a household, and conduit plus panel capacity prepared for 4 more bays. If the survey had found 12 EV households instead, the same sequence argues for fitting more bays at once — the method is the content, not the numbers.
Hardware for the 20-Unit Scale
For shared bays, the EV-AC03201T dual-connector AC station puts two Type 2 connectors on one wallbox per bay, the EV-ACT3204PE is a 22 kW three-phase Type 2 wallbox with RFID and app control, IP66, CE. EVDANCE is a Shenzhen manufacturer founded in 2011, exports to 30+ countries, and carries a 3-year standard warranty. Building teams can start from the residential charging page.
Frequently Asked Questions
How many chargers should a 20-unit building start with?
As many as the survey of actual EV households supports as a shared pool — the worked example above starts with 4 bays for 5 EV households, but those figures are invented to show the method. Count your own drivers first; a ratio copied from another building sizes the wrong thing.
What if the panel cannot feed every charger at full power?
That is a design question for the project’s licensed electrician: circuits can be planned so the installed chargers run within the confirmed capacity — through charger ratings chosen for the supply, and staged fitting as capacity allows. Never solve it by oversizing breakers; the 125% continuous-load rule is not negotiable.
How do residents pay in a shared pool?
Sessions are recorded per user through RFID or the app, and the building settles them under its own written rule — per kWh where local rules allow, or as a periodic fee. Our guide to charging in shared apartment and condo parking covers the arrangements.
Related Reading
- Adding EV Chargers to a Building: Load Calculation Basics
- Apartment and Condo EV Charging: Solutions for Shared Parking
- RFID and User Management for Shared EV Chargers
- How to Charge an EV When You Live in an Apartment
