Smart Energy Meter Case Study: 640-Unit Tower Sub-Metering

The owner of a 640-apartment tower was reading meters by hand once a month and chasing arrears afterwards. Two readers needed three days for one cycle, and disputes over estimated bills were routine. We supplied 658 smart energy meter points, wired to gateways that report over the mobile network. Manual reading has stopped, and tenants now pay before they consume.

Project Snapshot

The Problem: A Building Full of Meters Nobody Wants to Enter

Sub-metering in a large residential block creates a set of problems that have nothing to do with measuring electricity.

Access came first. Readers needed to enter 14 riser rooms and, in a third of the cases, to knock on a door to reach a meter inside an apartment. Every missed visit became an estimate, and every estimate became a dispute at the end of the quarter.

Arrears came second. When supply is billed after use, the owner carries the debt. In a building with short tenancies, a tenant can leave owing two months of electricity that nobody recovers.

The owner wanted three outcomes at once: no more keys and no more visits, payment before consumption, and one dashboard that shows the whole building.

Why We Chose Prepaid DIN Rail Meters Over Manual Reading

Four routes were compared.

Keep manual reading and improve the paperwork. Excluded. Better forms do not solve access, and the arrears problem stays with the owner.

A third-party billing service using its own meters. Excluded. It moves the problem to a supplier, but the owner loses control of the gateway, the data and the tenant-facing app, and switching later means replacing hardware.

Token vending machines in the lobby. Excluded. Vending machines solve payment but not reading.

Prepaid meters with a private data path. Selected. Per-apartment fee-control meters cut supply at a set credit level, and the data travels through the owner's own gateways, so the building keeps control of its metering assets.

The Smart Energy Meter System We Supplied

The system is built from three parts, and each was chosen for the building rather than from a catalogue.

At the apartment level we supplied fee-control single-phase meters. They sit on DIN rail inside the consumer unit, measure consumption, and cut supply when credit runs out. Residents top up through the operator's payment channel and the credit appears at the meter.

At the retail level we supplied the 4G DIN rail three-phase smart meter. Shop units have different loads, different hours, so they needed a three-phase device in the same rail format.

For collection we used our power data gateway. Meters report to the gateway over LoRa, which covers a riser stack well and needs no per-apartment SIM, and the gateway uploads over the mobile network. That split matters in a tower: one data plan per riser instead of 658 of them. The software layer records consumption by unit, flags tamper events and produces the monthly statement the office already sends.

Installation: How the Work Ran

Work moved riser by riser, with the building fully occupied.

Each riser was isolated for a morning only. The electrician removed the old metering, fitted the DIN rail units and the sealing covers, then re-energised and verified polarity, phase rotation on three-phase points and load direction. The gateway went into the top cabinet of the riser, and the LoRa signal was checked from the lowest and the furthest meter, which are the two points that fail first in a concrete riser shaft.

Two steps happened after the hardware. First, the office imported the tenant list with apartment numbers, meter numbers and opening readings, so the first invoice reconciled against the old register. Second, residents were given a short briefing on topping up, because a prepaid meter with no explanation produces a call at midnight.

The whole building was converted in 21 days, with no apartment off supply for more than half a day.

Testing and Quality Control

At the factory, every meter was calibrated and checked against a reference source before packing, and the results were recorded against the unit serial number. We also verified the nameplate, the tariff parameters and the firmware version for this project, since a wrong parameter table shows up later as an unexplained bill.

On site we ran three checks per riser. We compared each meter against a portable reference at a known load. We confirmed that every unit reported to the gateway with the right apartment number. And we tested the credit cut-off on a sample of apartments, because that is the function residents notice first.

The building's own electrical contractor then repeated the loop with our engineer present and signed the riser sheets.

Results: What the Numbers Show

All 658 points are live on the gateway. Monthly manual reading has stopped, which removed three days of work per cycle and the estimated bills that came with it, and the office now works from one statement generated by the platform rather than from 640 paper slips.

Arrears fell sharply, because credit is collected before consumption. Where a tenant leaves owing money, the balance is limited to the last top-up rather than to two months of usage. Tamper and reverse-flow events are flagged automatically, which the old system simply could not see.

The DIN electric meter installation notes from a comparable project cover the same commissioning sequence.

What This Case Means for Your Project

Sub-metering is a data project with a hardware component, not the other way round. Decide first who owns the gateway and the tenant data, then choose meters that fit the existing consumer unit, then design the collection path around the building's real geometry.

We build single-phase and three-phase smart meters, fee-control units, DIN rail meters and gateway terminals, and we supply them under OEM and private label terms for utilities, distributors and contractors. Send us your single-line diagram and unit count, and contact the team for a metering layout, a communication plan and a quotation.