Societies tend to over-count the points and under-build the route that feeds them. A car parked from evening to morning has many hours to absorb what it needs, so one shared point can often cover several vehicles rather than one; the arithmetic below tests that against your own residents' kilometres. The point count is rarely the hard question. The harder ones are how much cable route, conduit, spare breaker space and metering headroom you provide at the first dig, and what measurable trigger releases the next batch of points. Size the backbone once, install points in phases, and write the phasing into your policy.
Why counting today's EVs gives you the wrong number
The first figure anyone reaches for is the number of electric vehicles parked in the compound today. It is easy to collect and close to useless, because it fails in two opposite directions.
It can under-count: some residents may be holding off precisely because there is nowhere to charge, and that demand only surfaces once the first point goes live. It can equally over-count, when a committee reacts to a cluster of purchases and leaps to one point per car, tying up money in hardware that stands idle. The EV count is a stock; what you are sizing is a flow, in units per week spread across the hours cars stand still.
Survey intent instead
A one-page circular, collected flat by flat within a fortnight, gives a far better basis. Keep it short enough that people finish it.
- Do you use an electric vehicle now, and is it a two-wheeler or a car?
- If yes, how many kilometres a week? Read the odometer rather than estimating.
- If no, how likely is a purchase within twelve months, and within twenty-four?
- Would you use a shared point at a society-fixed rate, or want a private one?
Take current owners at face value and discount stated intent. Keep two-wheelers in a separate column, since they draw far less. Repeat the survey each year, so the next phase rests on a trend line rather than an argument, as putting EV charging on the AGM agenda explains.
Simultaneous demand, total demand and dwell time
The figure that alarms committees is the total: households multiplied by charger rating. It is real only if every vehicle plugs in at the same instant and draws full power all night. Cars do not arrive together, and a vehicle stops drawing once it has taken what it needs.
Work it with your own inputs. Suppose a resident's car takes about 10 units on the nights it charges and the point delivers 3.3 kW; substitute the units your owners read from their own displays. That is roughly three hours of draw, after which the bay is occupied but the load has gone. Across a ten-hour parking window, demand exists for under a third of the time.
Staggered starts, a rota or a controller that caps total draw can let several points share capacity that would not carry all at once. What your building can carry is a question for a licensed electrician who has measured existing maximum demand at your board, never one to infer from nameplate ratings. See sanctioned load and EV charging.
Dwell time makes a public site and a society car park opposite problems. An operator sells throughput, so power per point is everything; residents leave cars standing, so the constraint moves elsewhere.
| Design question | Public charging site | Society overnight parking |
|---|---|---|
| Vehicles served per point per cycle | Several, one after another | One, unless someone moves the cable |
| Effect of a slower charger | Fewer vehicles served, less revenue | Often none, if the parking window is long |
| What limits the build | Power available at each point | Route, protection and metering to each bay |
A modest charger left running through the parking window can deliver more energy than a day's driving consumes, so the rating deserves its own arithmetic rather than a default to the largest option, as in 3.3 kW versus 7.2 kW charging for apartment use.
Turning the survey into a point count
Do the sizing in units per week rather than in cars. It runs inside one committee meeting.
- Add the weekly kilometres reported by households that will use the facility.
- Convert to units using the figure each owner reads from their own display, not one you assume.
- Divide the weekly total by the charger power to get charging hours needed per week.
- Count the hours a bay offers per week, less the hours nobody will use.
- Divide, round up, and add one point if the result sits close to a whole number.
An illustration, with every figure one to replace with your own: suppose five households commit, their odometers add to 900 km a week between them, and their displays show about 7 km per unit, which each owner must confirm rather than borrow from a neighbour. That is about 130 units a week. At 3.3 kW that is close to 40 hours over seven nights, under six hours a night. One point covers the energy; a second settles the argument about who plugs in first.
That arithmetic is why one point often stretches across several committed users, and it collapses in cases you should test for: a vehicle used commercially, floating rather than allotted parking, or a cable route reaching few bays. Once the count is defensible, budgeting a society charging station picks up from there.
Build the backbone now, install the points in phases
The cheapest capacity you will ever buy is what you provided for while the trench was open. Hardware on the wall is replaceable; the route through the building is disruptive to redo. Ask your electrician to design for the end state and install for the first phase.
- Conduit with spare capacity and a draw wire left in place for later cables.
- A cable route and cross-section chosen for the eventual number of points, not the first two.
- Spare ways in the distribution board, and room to extend or add an enclosure.
- A metering arrangement that can accept more sub-meters without rewiring.
- Earthing designed around the final layout of bays, not the first bay served.
- An as-built drawing, dated and signed, kept with society records.
Every item there touches wiring, protection or earthing, and each must be specified for your site by a licensed electrician who has inspected it. Nothing here replaces that visit; our notes on what an electrician checks in a site assessment and cable routing in apartment buildings only help you ask better questions.
Trigger points for the next phase
A phase should be released by recorded data, not by whoever raises their voice. Log usage from the day the first point is energised: sessions, units, which bay, and every occasion a resident wanted a slot and could not get one. Then set triggers the committee can verify from it, at thresholds your general body agrees.
- Occupancy above an agreed share of usable night hours over a rolling quarter.
- A waiting list of a stated size that has not cleared within one month.
- Residents unable to obtain a slot more than an agreed number of times a month.
- A new EV that the existing rota demonstrably cannot accommodate.
Pair every trigger with a graded response. The first is often not hardware: a better rota, agreed windows, or a norm about unplugging a finished car buys capacity for nothing, which is why the conventions in shared charging etiquette repay early adoption.
Writing the phasing into the policy so you do not refight it
The expensive part of phase two is rarely hardware. It is the second round of persuasion, before residents who thought the matter settled. Decide the sequence once and record it.
- State the approved end state: how many bays are eventually served, and which.
- Separate the infrastructure funded now from the points installed now.
- Define each trigger in measurable terms, naming the usage log as the source of truth.
- Name who verifies a trigger, and the period within which they must act on it.
- Cap what the committee may spend per phase, and name the fund it comes from.
- Require a fresh written assessment from a licensed electrician before each phase.
That is delegation within a stated limit rather than a blank cheque, which is usually what carries the vote. How far you may delegate, and what majority the resolution needs, depend on your society's own by-laws and the practice your general body accepts, so read them and take advice from an appropriate local professional before drafting. For wording, see our clause-by-clause walkthrough of a society EV policy, and for the proposal, how to propose a common EV-charging station.
Common questions
How many EV charging points does a housing society need?
No fixed ratio applies everywhere. It depends on how far your residents drive and how long their cars stand still. Total the weekly kilometres of the households that will really use the facility, convert to units using each vehicle's own display, and divide by the charger power. Run it with your own figures: the answer often lands on one point serving several committed users rather than one per car, but a compound with long-distance drivers will not behave like its neighbour.
Is one charging point enough for a society with 100 flats?
The flat count is not the input that matters; the number of committed users is. One point can be adequate for the first few EV owners in a large society and inadequate in a small one where four residents drive long distances daily. Add a second when the log shows the first is genuinely constrained, or for redundancy against a fault.
Should we install a charging point at every parking bay?
Rarely, and the reason is money rather than principle. Points are the cheap, replaceable part and date quickly, so buying them ahead of demand irritates residents who funded idle equipment. Provide instead for the route at every bay you may one day serve: conduit, spare capacity, board space and metering that can grow. Each later point is then a short job, not a fresh excavation.
What if more residents buy EVs than we planned for?
That is what the phased design protects against, provided the backbone was built for the end state. Try the cheaper responses first: a rota, agreed windows, or a convention that a finished vehicle is unplugged. If the log still meets your trigger, the policy should already let the committee add points within a capped budget, after a fresh electrician's assessment.
Can we start with one point and add more later?
Yes, and it is usually the sensible route, on two conditions. The route, conduit, earthing and board capacity must be designed for the eventual number of points, because retrofitting those is what makes later phases painful. And the trigger for the next phase, with the authority to spend, must sit in the policy from the outset.