If your committee is weighing its third EV charger request, the real question is no longer whether to allow charging but whether to keep approving one cable run at a time or build a single shared route once. The answer is a break-even count you can work out on your own figures: divide the cost of the shared backbone by the saving each resident makes by dropping off it instead of pulling a full-length run, and that is the number of adopters at which the shared route becomes the cheaper path. Below that count, keep approving individual runs; at or beyond it, build the backbone.
The choice a committee actually faces
There are two ways to get power from your electrical room to a parking bay. In an individual run, each resident's cable travels the full distance from the board to their bay, in its own conduit, owned by that resident. In a shared route, the society builds one containment backbone — a tray or trunking — along the aisle once, and each resident pays only for a short drop from the backbone to their bay.
Approving one run at a time feels cheaper because no shared money is spent and each resident carries their own bill. That holds for the first request, and often the second. By the tenth it is the problem: a ceiling fills with parallel conduits laid on different days by different contractors, and every later fault trace, addition or inspection has to work around the ones already there.
The break-even sum on your own numbers
The whole decision reduces to one comparison. For a given number of adopters, add up what the individual-run path costs, add up what the shared-route path costs, and see which is lower. The count where the two meet is your break-even. You need four figures, and every one comes off your own building and your own contractor's written quote, not off this page:
- The corridor length from your electrical room to the farthest bay, in metres — measure it.
- The per-metre price to pull one full individual run — from a written quote for one resident's cable, conduit, fixings and labour.
- The per-metre price to build the shared backbone — the supply-and-install figure from the same contractor's quote.
- The length of a short drop from the backbone to a bay, and the number of residents you expect to adopt within a few years.
Now the sum. Suppose your corridor is 60 metres. Suppose the quote for a full individual run reads ₹350 per metre, so one resident's run works out at 60 × ₹350 = ₹21,000 — substitute the figure from your own quote. Suppose the shared backbone reads ₹1,100 per metre, so the backbone works out at 60 × ₹1,100 = ₹66,000. Suppose each drop off the backbone is 5 metres, at the same ₹350 per metre, so one drop is 5 × ₹350 = ₹1,750.
With those assumptions, the individual-run path for a number of adopters is that number × ₹21,000; the shared-route path is the one-time ₹66,000 plus that number × ₹1,750 for the drops. Setting them equal, adopters × 21,000 = 66,000 + adopters × 1,750, giving adopters × 19,250 = 66,000, so the count is about 3.4 — the shared route overtakes individual runs between the third and fourth adopter.
Check it both ways. At three adopters, individual runs cost 3 × ₹21,000 = ₹63,000 against the shared route's ₹66,000 + 3 × ₹1,750 = ₹71,250, so individual runs are still cheaper. At four, ₹84,000 against ₹66,000 + 4 × ₹1,750 = ₹73,000, so the shared route has pulled ahead. This is why the third request is the moment to decide: the fourth resident tips it.
The rule in one line: break-even is the backbone cost divided by the saving per resident of a drop over a full run — here ₹66,000 ÷ (₹21,000 − ₹1,750) ≈ 3.4. Put your own four figures into that line, or into the apartment charger cost calculator. A long corridor and a wide gap between run and drop prices push the break-even down; a short corridor pushes it up.
Score the two paths side by side
The committee also has to live with the choice for years. These are the qualitative differences, kept apart from price.
| What to weigh | Individual run per resident | One shared route |
|---|---|---|
| How cost behaves as each new adopter joins | Rises in a straight line — every resident pays a full run | A large first outlay, then only a small drop per resident |
| Who owns and maintains it | Each resident owns their own cable and conduit | The society owns the backbone; residents own their drops |
| What the committee approves each time | A fresh route, fixings and slab penetrations for every request | The route once; later requests are short drops onto it |
| Effect on the basement over time | Parallel conduits accumulate along the ceiling | One organised path, planned in a single layout |
| Effect on future maintenance and fault tracing | Each addition has to work around the runs already there | Additions and inspections follow one documented route |
| What has to be settled before the third request | Little — but the saving is being lost with every run | Funding, ownership and the electrician's sign-off, once |
When a shared route is not worth building
The same sum can just as easily tell you to keep approving individual runs. Building shared containment ties up society money and committee time, and several common situations never reach the count that would justify it:
- Few likely adopters. If your building has only a handful of bays, or interest is thin, you may never pass three or four adopters. A backbone that three residents ever use is the more expensive path.
- Short runs from a nearby board. Where the board sits close to the bays and each run is a few metres, the full-run price and the drop price are almost the same, the saving per resident nearly vanishes, and the break-even climbs out of reach.
- Open stilt parking. Where bays sit in open stilt or surface parking rather than a long enclosed aisle, there may be no single corridor a backbone would follow, and short direct runs can be the simpler answer.
- A short corridor. The maths turns on length. A fifteen-metre route rarely justifies a shared backbone the way a sixty-metre one does, because the full run it would replace is so much shorter.
For a single resident weighing how their own cable should reach their bay — rather than a committee weighing shared infrastructure — the route choice is covered in cable routing options for apartment buildings. If you are still sizing the demand, work through how many charging points your society actually needs first, because that count feeds straight into the break-even.
What to put in writing to your electrician and fire consultant
A shared route carries several circuits, and none of its safety questions are the committee's to answer. Put these to a licensed electrician, and to your fire consultant where the route crosses fire-rated construction:
- Which containment type they will design and certify for your basement, and why that one.
- What clearance they need between the route and sprinkler heads, water lines and drainage.
- How they will firestop each slab or wall penetration the route makes.
- What grouping correction factor they apply, since bundled cables run hotter than one cable in free air, and how that changes conductor sizes.
- Whether the containment needs bonding and earthing, and how it ties into the building's existing earth.
That fourth point is real physics: bundled conductors run hotter, so a shared route's sizing differs from a lone cable's, and it is the electrician's calculation, not a number to read off a website. For the questions specific to running cable through a basement, see basement parking checks for EV charging and, for the bonding question, earthing basics for apartment EV charging.
Should you lay spare capacity now?
Once a committee decides to build the backbone, the next question is how much of it to build. Laying extra capacity while the route is open — space for residents without an EV yet — is cheaper per future connection than reopening the ceiling later, since the labour and disruption are paid for once. Against that, unused capacity is idle money, and the more you provision, the larger the first outlay the break-even must justify.
Treat it as its own small sum. Suppose the backbone for today's adopters is quoted at ₹66,000 and a larger one sized for future demand adds ₹20,000 — substitute your own quote. Divide that ₹20,000 by the number of future residents you genuinely expect, and compare the per-head figure against what a fresh individual run would cost each of them later. If it is clearly cheaper per future adopter, do it; if demand is thin, do not.
How the first outlay and any spare capacity are funded, and how residents who join later buy in, is a fairness question to settle in the same meeting — who pays for apartment EV wiring and how to split shared charging costs set out the options, and the wider capital picture sits in budgeting a society charging station.
Common questions
At how many EV owners does a shared route become cheaper than individual runs?
At the count where the one-time backbone cost is covered by the saving each resident makes by taking a short drop instead of a full run. Work it out as backbone cost divided by (one full run minus one drop), using figures from your own contractor's quote and your own corridor length. It is a number for your building, not a fixed threshold, and it moves with length and the gap between run and drop prices.
When is a shared route not worth building?
When your building is unlikely to pass that break-even count. Few likely adopters, a board sitting close to the bays so runs are short, open stilt parking with no single corridor to follow, or a short route where a full run is not much longer than a drop can each keep individual runs the cheaper choice. Run the sum on your own numbers before committing shared money.
Who funds the shared route, and how is it recovered from residents who join later?
That is a decision for the committee, and there is more than one workable answer — a common reserve, a joining contribution, or a buy-in from each resident as they connect. Whichever you choose, agree it in writing before building, including how a later joiner pays their share of a backbone that earlier residents funded.
What should the committee ask its electrician and fire consultant to confirm in writing?
Which containment they will design and certify and why, what clearance they need from sprinkler heads and water lines, how they will firestop each penetration, what grouping correction factor they apply to the bundled cables, and how the route is bonded and earthed. Get these in writing before money is committed; the answers are theirs to give, not the committee's to assume.
Should we lay spare capacity for residents who do not own an EV yet?
Sometimes. Building spare capacity while the route is open is cheaper per future connection than reopening the ceiling later, but capacity nobody uses is idle money and it enlarges the first outlay. Treat it as its own small sum: the extra cost divided by the number of future adopters you genuinely expect, against what a fresh run would cost each of them. Provision ahead only when that comparison clearly favours it.