How much should a later EV owner pay the neighbour who funded the shared cable? The fair answer is not a fixed fee but a formula: take the shared portion's original cost from the first mover's own invoice, decide how many years you expect it to last, write down its remaining value on the day each new resident connects, and divide that value by the number of residents then sharing it. A cable that is part-way through its life is worth less than a new one, so a resident joining in year four pays less than one who joined in year two. Agree the rule in writing before the first installation, because retrofitting fairness after money is spent is what fails.
Why "just split it equally" breaks down
When one resident pays for a shared backbone so that others can later take a short drop off it, the society owes them a way to be repaid as those others join. The tempting answer is to divide the original cost equally: if it served four in the end, each pays a quarter. That feels fair and is easy to defend at a meeting, but it ignores time. A resident connecting in year six is buying into a cable with most of its life behind it, yet an equal split charges them the same as the first mover paid for a new one. The argument that follows is predictable and bitter, and it is the reason this needs a rule set down in advance.
This page is only about splitting that cost. The physical route, its sizing and its safety belong to a licensed electrician, and who pays for what in the first place is worked through in who pays for apartment EV-charger wiring, which names first-mover-funds-then-others-reimburse as one fair pattern but stops short of the number. This page supplies the number.
Three ways to set a later joiner's share
There are three rules a society can adopt. Score them on what the first mover gets back, what a late joiner pays, what the committee has to track, and the argument each one tends to produce.
| What to weigh | No reimbursement | Equal share, re-split each time | Depreciated share |
|---|---|---|---|
| What the first mover recovers | Nothing — they carry it alone | A large sum, but it keeps changing as each new owner joins | A predictable amount that declines the longer they wait |
| What the fifth joiner pays | Nothing | An equal one-fifth of the original, though the cable is now old | A small sum reflecting the life the cable has left |
| What the committee tracks | Nothing | Every past payment, re-divided at every joining, indefinitely | One invoice and one connection date per resident |
| On a flat sale | Nothing to settle | Hard — past splits must be reopened | The paid-in value transfers with the flat; clean |
| The argument it produces | The first mover feels used | Late joiners feel overcharged for an old cable | The fewest disputes, because age is priced in |
No reimbursement suits a society where the first mover genuinely volunteered to gift the backbone, and nothing more need be said. Where they expect to be repaid, the depreciated share is the rule that survives contact with real dates, and the rest of this page runs it.
The depreciation formula, in plain steps
Straight-line depreciation is the only arithmetic involved, and you can run it on paper. Every figure below is an assumption chosen to show the working — substitute your own.
- Take the shared cost from the invoice. Suppose the first mover's own invoice for the backbone — the part later residents will share, not their private drop — reads ₹80,000. Use the figure on your invoice.
- Choose a useful life. Suppose the society decides the backbone should last 10 years before it is written down to nothing. You choose this number, and you should choose it openly; a longer life makes late joiners pay more, a shorter one less.
- Find the yearly write-down. ₹80,000 ÷ 10 = ₹8,000 a year. After a years, the remaining value is ₹80,000 − (a × ₹8,000).
- Value it on the joining date. When a new resident connects, read off the remaining value for the backbone's age that day.
- Divide by the residents now sharing it. The joiner's buy-in is that remaining value divided by the number of residents connected once they join.
That buy-in is credited back to the residents already on the backbone, so that over time everyone contributes toward the value they actually shared. Routing it through the society's books, rather than resident-to-resident, keeps the record clean and makes a flat sale simple to settle.
A worked recovery curve as owners join
Keep the ₹80,000 backbone and the 10-year life, so the remaining value falls by ₹8,000 each year. Suppose owners join in years 2, 4, 6 and 8.
| Who joins | Backbone age | Remaining value | Residents after they join | Their buy-in (value ÷ residents) |
|---|---|---|---|---|
| 1st (funds it) | 0 | ₹80,000 | 1 | pays the full ₹80,000 |
| 2nd | 2 years | ₹64,000 | 2 | ₹64,000 ÷ 2 = ₹32,000 |
| 3rd | 4 years | ₹48,000 | 3 | ₹48,000 ÷ 3 = ₹16,000 |
| 4th | 6 years | ₹32,000 | 4 | ₹32,000 ÷ 4 = ₹8,000 |
| 5th | 8 years | ₹16,000 | 5 | ₹16,000 ÷ 5 = ₹3,200 |
Now trace what the first mover gets back. Each buy-in is credited equally among the residents already connected before that joiner. The second owner's ₹32,000 goes to the first mover alone. The third owner's ₹16,000 splits between the two before them, ₹8,000 each. The fourth owner's ₹8,000 splits three ways, about ₹2,667 each. The fifth owner's ₹3,200 splits four ways, ₹800 each. The first mover therefore recovers ₹32,000 + ₹8,000 + ₹2,667 + ₹800 = ₹43,467 by the time the fifth connects, leaving a net cost of ₹80,000 − ₹43,467 = ₹36,533 for the years they had sole or near-sole use.
The curve tells the honest story the flat split hides: the first mover recovers most from the earliest joiner and less from each one after, because the cable they are all buying into is worth less every year. A resident who waits until year eight to connect contributes little, and that is correct — there is little value left to buy. Run the same table with your own invoice figure and your own chosen life; the shape does not change.
What has to be written down before the first installation
The formula only holds if the inputs are recorded when they are known, not reconstructed years later from memory and a group chat. Put these into the society's EV policy before anyone digs:
- The shared cost. A copy of the first mover's invoice, with the shared backbone separated from their private drop, filed with the society.
- The useful life. The number of years the general body agreed, and the yearly write-down that follows from it.
- The connection register. Each resident's connection date, the backbone's age that day, the value used, and the buy-in they paid — one line per resident, held by the treasurer.
- The credit rule. That buy-ins are credited to residents already connected, and that the register is published to the members who are party to it.
- The sale rule. That a resident's paid-in position transfers to the buyer of their flat, so nothing is reopened when someone moves.
Draft this alongside the wider scheme with the society EV-charging policy draft and the RWA EV policy generator, and keep it with the capital plan in budgeting a society charging station. Settling it in advance is the single thing that prevents the dispute in resolving EV charging billing disputes from starting.
Common questions
What is a fair basis for setting a later joiner's share?
The remaining value of the shared cable on the day they connect, divided by the number of residents then sharing it. This prices in age: a joiner buying into a part-worn cable pays less than an early joiner bought into a new one. It is fairer than an equal split of the original cost, which charges a late joiner as if the cable were new, and fairer than charging nothing, which leaves the first mover carrying a shared asset alone.
How do we apply depreciation when nobody knows how long the cable will last?
You do not need to know exactly; you need the general body to agree a figure and apply it consistently. Pick a plausible service life, write the value down in equal yearly steps to zero, and record the choice so it is not re-argued each time. A longer life shifts more cost onto late joiners, a shorter one onto the first mover, so choose it openly with both in the room.
Should the money go to the first mover directly, or to the society?
Route it through the society's books. The society receives each buy-in and credits it to the residents already connected, keeping one register everyone can see. Resident-to-resident payments leave no shared record and become impossible to audit once a flat changes hands. A single ledger line also makes the sale rule enforceable.
What happens to the arrangement when the first mover sells the flat?
Their paid-in position should transfer with the flat to the buyer, who steps into the same place in the register. Because the value is recorded against the flat rather than the person, nothing has to be reopened or recalculated on a sale. Write this into the policy at the start; it is the clause that stops a change of ownership unravelling the whole scheme.
What has to be agreed before the very first installation?
The shared cost from the invoice, the useful life and yearly write-down, the connection register, the credit rule and the sale rule — all recorded in the society's EV policy before any cable is laid. Retrofitting fairness after the money is spent is the thing that fails, because the people who would have to agree to it are the ones it now costs.