Energy monitoring guide
What is an energy monitoring system? How it works in a factory, part by part.
An energy monitoring system reads the meters in your plant every few seconds and turns them into live readings, history, alerts and bill figures. Here is what each part does, how a reading travels from the cable to your phone, what the system measures, and what to check before you choose one.
What an energy monitoring system is
An energy monitoring system measures how much electricity a site uses, when it uses it and where. It reads meters on the supply and on each panel, keeps every reading as history, and shows the result on a dashboard.
The DISCOM meter gives you a total for the month. A monitoring system gives you the story behind that total: which interval set the peak, which panel kept running at night, and what each of those cost on your bill.
Meters measure, a gateway collects, software explains, and your team acts.
You will also hear it called an electricity monitoring system or a power monitoring system. In data centres and hospitals the usual term is EPMS, electrical power monitoring system. The parts are much the same. What changes is what each one records and who reads it.
The parts of an energy monitoring system
| Part | What it does | Where it sits |
|---|---|---|
| Current transformers (CTs) | Step the load current down to a small current, usually 5 A or 1 A at full rating, that the meter can measure | Around the cables or busbars of each feeder |
| Multifunction meter (MFM) | Measures voltage, current, power, power factor and energy, and keeps running totals | On the panel door, one per feeder |
| RS-485 network | Carries the readings of many meters over one twisted-pair cable, using the Modbus RTU protocol | Run from meter to meter, and panel to panel |
| Gateway | Reads each meter in turn, records the history and raises alerts | Inside the plant, usually in a panel |
| Software and dashboard | Turns readings into demand, power factor, bill and savings figures | In a browser on any phone or laptop |
| Actions | Alerts to the right person, reports, and automatic control where it is set up | On phones, and through I/O cards in the panel |
On an HT supply, potential transformers (PTs) step the voltage down for the incomer meter as well. On LT panels the meter usually reads the voltage directly.
How it works, step by step
- The CT senses the current. A CT on each phase gives the meter a small current in proportion to the load. The CT ratio, such as 400/5, is set in the meter so it shows the real current.
- The meter does the maths. The MFM measures voltage and current on every phase and works out kW, kVA, kVAr, power factor and frequency. It keeps adding up kWh and kVAh, much like the DISCOM meter.
- The gateway asks each meter. Every meter on the RS-485 cable has its own address, called a slave ID. The gateway asks each one for its readings, every few seconds, and stores the answers with the time.
- The software builds intervals. Readings are grouped into 15- or 30-minute intervals, the way your DISCOM works out Maximum Demand, and into hourly, daily and monthly totals.
- Your tariff turns units into rupees. Demand, power factor, TOD zones and energy are priced on your own tariff, so you can see what each panel and each hour cost.
- Alerts and action follow. When a reading crosses a limit you set, the right person is told. Where control is part of the project, the system can also hold back chosen loads on its own.
What it measures
| Reading | Unit | Why it matters |
|---|---|---|
| Active power | kW | The power doing useful work right now |
| Apparent power | kVA | What the supply carries, and what kVA Maximum Demand is billed on |
| Reactive power | kVAr | The part that does no work and drags power factor down |
| Power factor | PF | Below the limit it brings a surcharge, and on a kVAh bill every unit costs more |
| Voltage and current per phase | V, A | Loading on cables and breakers, and whether the phases share the load |
| Frequency | Hz | Supply stability, and when the plant is running on DG |
| Energy | kWh, kVAh | The units you are billed for, and the units each panel used |
| Harmonics | THD % | Distortion from drives and UPS that heats transformers and shortens capacitor life |
From those readings the software works out the figures your bill is really made of:
- Maximum Demand: the highest 15- or 30-minute average in the month, and the interval running right now. See MD penalty.
- Load factor: average demand divided by Maximum Demand. Try the load factor calculator.
- TOD split: units used in peak, normal and off-peak hours. See TOD tariff.
- Idle load: power drawn while nothing is being made. See machine running and idle time.
- Energy per unit made: kWh per tonne, piece or batch, once production is entered. See specific energy consumption.
Types of energy monitoring systems
| Type | How it measures | Good for |
|---|---|---|
| Home and plug monitors | A clamp or smart plug in a home or small shop, usually over Wi-Fi to an app | Seeing which appliance uses what |
| Building monitoring | Meters on the main panels of offices, malls, hotels and hospitals, often next to a BMS | Air conditioning, lighting and tenant energy |
| Industrial monitoring | Panel MFMs in factories and process plants, on a wired RS-485 network | Demand, power factor, TOD, idle load and cost per unit made |
This guide is about the industrial kind. A factory needs wired meters that keep reading through heat, dust and electrical noise, and figures in the same terms as its HT or LT bill. For buildings, see commercial buildings and campuses.
Energy monitoring, power monitoring and energy management
These terms overlap, and vendors use them loosely. This is what each one usually means:
| Term | What it usually means |
|---|---|
| Energy monitoring | Energy and cost over time: units, demand and the bill, panel by panel |
| Power monitoring | The supply itself: voltage, unbalance, harmonics, sags and swells. See power quality. |
| EPMS | Power monitoring for critical sites such as data centres and hospitals, often with breaker status and event records |
| Energy management | Monitoring plus targets, alerts, action and proof of the saving. See energy management system. |
| EMS in SCADA | In power utilities, the software in a grid control centre that uses SCADA data to balance generation and load. A different product from a factory EMS. |
For how an EMS sits next to plant automation, see EMS vs SCADA vs BMS.
What it catches in one month
Take a sample HT bill: Contract Demand 500 kVA, 1,87,000 kWh and a month-end power factor of 0.87. The bill gives the totals. Monitoring shows the time and the load behind each avoidable charge.
| Charge | What monitoring shows | Avoidable |
|---|---|---|
| Excess demand | Demand reached 560 kVA against 500 kVA when heavy motors started together at 11:42 on Day 24. Day 15 had already touched 96%. | ₹46,800 |
| Peak-hour surcharge | At 19:30 the plant was close to full load inside the peak window, when every unit costs 15% more. | ₹31,200 |
| Idle load | Hidden inside energy charges. At 02:20 Machine 2 drew 6.2 kW with production at zero, and four shut Sundays used 856 kWh. | ₹22,900 |
| Power factor surcharge | Motors pulled PF down to 0.84 at 14:30, under the 0.90 limit. The month closed at 0.87. | ₹18,400 |
| Total | Out of ₹16,99,845 payable: four causes, each with a time and a load behind it | ₹1,19,300 |
Illustrative figures from a sample HT bill. Rates, limits and surcharges differ by state and DISCOM.
None of these four shows up as a cause on the bill itself. The free bill check shows which of them is on yours.
Common mistakes
- Watching kW on a kVA-billed connection. If Maximum Demand is billed in kVA, a dashboard in kW hides the power factor gap. See kVAh billing.
- Keeping only hourly data. Maximum Demand is set by one 15- or 30-minute interval. An hourly average can hide the spike that set the bill.
- Panel meters with no incomer meter. Without the incomer, nobody knows whether the panels add up. A wrong CT ratio, or a CT fitted the wrong way round, makes it worse. See sub-metering.
- Readings with no rupees. Teams act on cost. A dashboard that shows only kW and kWh is soon ignored.
- Alerts with no owner. An alert sent to everyone is acted on by no one. Each alert needs a limit and a named person.
- History you cannot take out. Audits, finance reviews and bill disputes need the raw history. Check that it exports to Excel or CSV.
Where to start
Start where the money is. On most HT bills that is the incomer, because demand and power factor are billed there.
- Incomer. One meter on the main supply gives bill, Maximum Demand, power factor and penalty alerts from day one.
- Main panels. Feeder meters show where the energy goes, panel by panel.
- Every machine. Idle load, shift-wise use and cost per unit made, machine by machine.
- Every plant. Plants in other cities join one dashboard and one combined report.
For what to meter after the incomer, and how to keep the totals honest, see sub-metering and load monitoring. Before choosing a system, go through the buying guide.
Cloud or on-premises
Many systems send every reading to the vendor’s cloud. An on-premises system keeps the meters, history and dashboard inside the plant, and carries on recording and alerting when the Internet is down. Owners can still open it from anywhere over an encrypted private network. More in on-premises energy monitoring, and cost, security and outages side by side in cloud vs on-premises.
What decides the cost
Every plant is different, so every quote is too. These are the things that move it:
- How many panels already have meters with an RS-485 port, and how many need new meters and CTs.
- The cable runs between panels, and how many gateways the meter count needs.
- Whether automatic control through I/O cards is part of the project.
- Software updates and support, which usually come as a subscription.
How KONDUKTOR® EMS does it
KONDUKTOR® EMS is an energy monitoring system for factories and commercial buildings in India. Gateways read the multifunction meters on your panels over Modbus RTU: any brand, single- or three-phase, up to 10 meters per gateway. More gateways join the same dashboard as the plant grows. Each gateway records the history on site and serves the dashboard on your plant network. Nothing is sent to KONDUKTOR or to any cloud server.
- Live readings on every meter, with the running Maximum Demand interval against Contract Demand.
- Power factor, TOD split, idle detection and an estimated bill on your tariff.
- Load heatmap, shift comparison, before-and-after comparison and energy per unit made.
- Excel and CSV export, and a monthly CO₂e figure.
- After a power cut, logging restarts on its own and the gap is filled with estimated energy, so totals still match the meter.
Automatic control runs through Modbus I/O cards, engineered for your plant as part of your project: Maximum Demand limits, TOD load shifting and idle machine switch-off. See which meters connect.
Common questions
What is an energy monitoring system?+
A system that reads the meters on your supply and panels, keeps the readings as history, and shows them as live figures, alerts and bill costs. It shows when and where the energy went, not just how much.
How does an energy monitoring system work?+
Current transformers feed each meter, and the meter works out power and energy. A gateway reads every meter over an RS-485 cable using Modbus RTU and keeps the history. Software groups the readings into 15- or 30-minute intervals and prices them on your tariff.
What does an energy monitoring system measure?+
kW, kVA, kVAr, power factor, voltage, current, frequency, kWh and kVAh, and harmonics on meters that report them. From those it works out Maximum Demand, load factor, the TOD split, idle load and energy per unit made.
What is the difference between energy monitoring and power monitoring?+
Energy monitoring follows energy and cost over time: units, demand and the bill. Power monitoring watches the supply itself: voltage, unbalance and harmonics. Many panel meters measure both, so one system can show both.
What is EMS in SCADA?+
In power utilities, EMS is the software in a grid control centre that uses SCADA data to balance generation and load across the network. It is a different product from a factory energy monitoring or energy management system. See EMS vs SCADA vs BMS.
Do we need new meters?+
Not if your panels have multifunction meters with an RS-485 Modbus port, as most do. A feeder with no meter, or a meter with no RS-485 port, gets a new one.
Does an energy monitoring system need the Internet?+
Not with an on-premises system. The gateway reads the meters, records the history and raises alerts on site, and the dashboard opens on the plant network. The Internet is needed only to view it from outside the plant and for software updates.
How accurate is an energy monitoring system?+
As accurate as its meters and CTs. Panel multifunction meters are commonly accuracy class 1.0 or 0.5S, and CTs carry their own class. That is close enough to find leaks and check the bill, while the DISCOM meter stays the meter you are billed on.
See what your meters are already telling you.
Book a live demo and see live readings, Maximum Demand and bill figures from meters like yours.