One electricity bill. Many residents. A fair share for every one of them.
When a building buys power in bulk and re-bills the people living inside it, dividing that bill fairly is genuinely hard — because people move in and out. I built Wattey to measure what each person actually used, for the exact time they were there, and to put a photograph behind every number.
One bulk bill → fair per-resident bills
The parts add up to the whole — to the paisa. Illustrative; no real resident data.
- 265 beds
- ~160 sub-meters, billed as one fair bill each
- To the paisa
- books reconcile across mid-month move-ins and move-outs
- Measured
- not estimated — from real readings and real time present
The bill is easy. The people are the hard part.
A hostel, a student residence, a co-living space pays the utility one large bill each month and has to recover that money fairly from everyone inside. That would be simple if everyone stayed all month. They don’t.
the 12th
Someone moves in mid-month — they shouldn’t pay for the first 11 days.
the 20th
Someone leaves — and needs their final bill that day, not at month end.
3 occupants
One room, three people across the month — who owes what?
half in a week
At term start, half the building turns over in days.
Spreadsheets
Slow, error-prone, and impossible to defend when a figure is disputed.
Estimates (RUBS)
Dividing by room size or headcount is a guess — the resident who was away all month pays like the one who ran the AC every night, and nobody can prove it’s fair.
Measured, not estimated.
I built Wattey to divide the bill the only way that’s actually fair — by what each person used and how long they were there, from real meter readings, with a photograph behind every one.
Fair to the day
Each resident’s bill starts the day they move in and ends the day they leave. Present nine days, billed nine days.
Backed by evidence
Every reading is captured with a photo of the meter, filed against the resident it concerns. Disputes are settled by the picture.
Settled on the day they leave
A mover-out’s exact final bill is ready immediately, so dues clear at the door — not at month end.
The books always balance
Everything billed across the month, leavers and stayers alike, adds up to exactly what the building consumed. To the paisa.
Reconciled to the utility bill
Each month, what was billed out versus what the utility charged — clearly, side by side.
Records you can defend
Once bills and payments are made, the figures are locked. Corrections happen on the record, with a trail — never a silent edit.
A bill that explains itself.
Each resident’s bill shows the days they were present, the meter readings behind it, and a photograph of every meter — so it settles a dispute by evidence, not argument.
Electricity bill
Room 204 · Bed B · demo month
| Meter | Start | End | Units |
|---|---|---|---|
| Room · main | 04 812 | 04 941 | 129 |
| Room · AC | 11 306 | 11 494 | 188 |
A photograph stands behind every reading. Illustrative — no real resident, amount or meter.
Proven before it billed a rupee
An automated proof suite walks a full month — arrivals, mid-month departures, settlements, payments and reversals — and asserts the books close every time.
300+
automated database & security proofs
70+
billing test cases
Independently stress-tested for correctness andsecurity — from an outsider’s and a low-privilege staff member’s position — before it handled real money.
Where the real work went.
Anyone can divide a number by a headcount. The difficulty — and where I spent the engineering — is getting it right under real-world mess, and proving it.
Time-accurate splitting
The month divides at each meter reading, and each segment is shared only among who was actually present in it — so a mid-month arrival never pays for electricity burned before they showed up.
Every resident’s own evidence
Each person’s reading is captured and filed against their name, with a photograph — turning “trust me” into “look at the meter.”
Books that provably close
Interim bills for leavers plus month-end bills for the rest sum to exactly what the building consumed — checked by an automated proof suite that walks a full month of arrivals, departures, payments and reversals every time.
A tamper-evident money ledger
Bills and payments can’t be silently changed; a reversal is recorded, not erased — which is what lets an operator defend a figure a year later.
Built for the messy cases
Rooms with two meters, one, or none; a commercial unit on its own rate; residents on negotiated rates; and fair rounding rotated rather than always landing on the same person — all handled, not assumed away.
Verified before it billed a rupee
Engineered and independently stress-tested for correctness and security — from an outsider’s and a low-privilege staff member’s position — so a resident’s data can’t leak and the money records can’t be tampered with.
Built for a real building, not a demo.
- 7
- floors
- 94
- rooms
- 265
- beds
- ~160
- sub-meters
Shared rooms, self-contained apartments, offices, common areas metered but never billed to a resident, and a commercial unit on its own rate — all under one roof, all billed correctly. Most rooms have two meters, some have one, a few have none; each case is handled rather than assumed away.
A management dashboard
For the office — rooms, residents, readings, bills, collection, and the monthly reconciliation.
A field app that works offline
Photograph each meter, read the number from the picture, sync when back in range — a basement with no signal is not a blocker.
One connection, many changing residents — the pattern repeats.
Anywhere a single bulk electricity connection serves people who come and go, the same problem appears — and residents who see a measured bill run the AC with one eye on what they’ll owe.
Built, verified, entering production.
The management dashboard runs end to end; the field app captures readings with photo evidence and offline sync; the billing engine is proven to balance across a full month of turnover before it touches real money. It is not yet a multi-building platform with live payment volume — the honest, stronger story is depth and correctness on a real 265-bed property.
Need something like this built?
I build production systems where correctness matters — energy platforms, billing, anything where the numbers have to be exactly right and defensible. If you’ve got a hard problem like this, let’s talk.
Start a conversationQuestions about Wattey — Fair electricity sub-billing
How is this different from dividing the bill by number of occupants?
That is an estimate. Wattey Sub-Billing measures each person’s actual share from real meter readings and the exact time they were present — not a RUBS-style formula based on room size or headcount. The resident who was away all month does not pay like the one who ran the AC every night.
What happens when someone moves in or out mid-month?
Their bill starts or ends on the exact day. A leaver’s final bill is ready the day they go, with the meter reading of that day behind it, so dues clear at the door rather than waiting for month end. Everything billed across the month still reconciles to exactly what the building consumed.
What if a resident disputes their bill?
Every reading has a photograph of the meter, filed against that resident, and the bill shows its own working — the days present, the readings behind it, and the photographs. Disputes are settled by evidence, not argument.
Does it work if a room has more than one meter?
Yes. Each meter is read on its own and the room’s real consumption is combined correctly. Rooms with two meters, one, or none, and commercial units on their own rate, are all handled rather than assumed away.
What kinds of buildings is it for?
Any building on one bulk electricity connection with residents who come and go — hostels, student housing and PBSA, co-living, serviced apartments, short-let and Airbnb portfolios, apartment blocks on a master meter, and worker accommodation.
Is it live yet?
It is built, independently stress-tested for correctness and security, and entering production for its first building — a 265-bed residential property in Lahore. The dashboard and field app run end to end; the billing engine is proven to balance across a full month of turnover before it handles real money. It is not yet a multi-building platform with live payment volume.