What is Sub Metering? Explore its Working, Benefits, Disadvantages, and Steps for Bill Calculation

Sub metering is the process of installing a separate water, gas, or electric sub meter for each tenant, apartment, shop, or department in a building so that every unit’s usage is recorded individually instead of lumping it all into one main bill. Unlike traditional master metering, where a single main meter tracks total building consumption, sub metering helps monitor electricity, water, and gas usage for individual flats, departments, or equipment.

Installing a sub meter for electricity usage is common in rented homes, apartments, office spaces, malls, and factories to ensure everyone pays only for what they consume. These smaller meters are connected after the main meter and give a clear picture of electricity, water, or gas usage at the unit level.

Electric sub meters are especially useful when you have multiple tenants. They’re also installed in commercial buildings or industrial plants to track department-wise energy consumption.

Installing an electric sub meter is beneficial for many reasons: 

• Sub metering helps with fair bill allocation: It means consumers only pay for what they use, not for what other tenants or departments have used. 
• A sub meter for electricity reduces bills and the load on the grid: Discoms usually charge more per unit during peak usage hours. Since an electric sub meter reflects that data to consumers, you can shift your consumption to low-demand hours. This will not only reduce your bills but also reduce the load on the grid, thereby decreasing the chances of an outage due to overloading.

Sub metering is perfectly legal in India. In fact, more and more homeowners, landlords, builders, and housing societies are adopting it to avoid disputes and enable transparent billing.

In this blog, we will explain what sub metering is, the sub meter price in India, the benefits and limitations of installing an electric sub meter, and how sub meters differ from main meters.

We will also explain how you can save 90% or more on your electricity bills by switching to on-grid rooftop solar panel systems for homes, housing societies, and commercial complexes and whether investing in rooftop solar is worth the ROI you get.

TL;DR Summary Box: What is the Difference Between Main Meter and Sub Meter in India?

A main meter is the primary meter installed by the electricity board that measures the total electricity used in an entire building or property. An electric sub meter, on the other hand, is a smaller meter installed after the main meter to track electricity used in a specific part of the building, like a single flat, tenant, shop, or office. 

Simply put, while the main meter is used for billing by the electricity provider, sub meters help divide the bill fairly among people or departments based on what each one actually used.

Here are the main topics covered in this blog in detail:

*Please note: The sub meter price listed above is indicative, and not fixed. The actual sub meter price in India can significantly vary from the given range based on the brand, manufacturer’s discount, and the product warranty. Besides, these are just the meter prices. Installation costs and charges of electricians are not included in this price range. SolarSquare does not promote any electric sub meter brand. We install on-grid rooftop solar for housing societies, homes, and commercial complexes. 

What is the Meaning of Sub Metering?

Sub metering is the installation of individual small meters within a property to measure utility consumption for specific tenants, departments, equipment or flats. Unlike a main master meter that tracks total utility consumption of the entire building, sub metering provides detailed usage details for each separate space. 

Sub metering helps property owners divide utility costs fairly based on actual consumption rather than estimates. Its primary benefits include accurate billing and energy conservation, as the electric sub meter shows peak usage hours, allowing users to shift their consumption to non-peak hours and reduce their bills.

What Can a Sub Meter Measure?

A sub meter is a smaller meter that’s installed after the main meter to track how much electricity is being used in a specific area, room, or flat inside a building.

Here are the main parameters sub meters can track:

• Electricity use: A sub meter for electricity can check how much power is being used by each flat, tenant, or office separately.
• Water use: It can measure how much water is being used, find leaks early, and track usage in flats or commercial buildings.
• Gas use: These meters can also monitor gas used for chores like heating and cooking.
• Peak usage times: Electric sub meters find out when electricity use is highest. Consumers can use this data to shift their consumption to non-peak hours and save on their energy bills, as discoms usually charge more per electricity unit during peak hours.
• Power efficiency: These meters can track how efficiently electricity is being used and identify any issues with voltage.

What is the Difference Between the Main Meter and the Sub Meter for Homes?

A main meter records the total electricity consumed in an entire building, which is used by the discom to generate the bill. A sub meter is installed after the main meter to track how much electricity is used in separate areas like individual flats, rooms, or offices. 

Sub metering helps owners know exactly how much power each consumer is using, and based on that, they can allocate the bills so people pay for their actual usage, instead of splitting the total bill equally.

Here’s a tabulated snapshot of the key differences between a main meter and a sub meter:

How Does Sub Metering Work?

Modern electric sub meter systems are smart digital meters that automatically record data and enable time-of-use tracking. In sub metering, small meters are added after the main meter, allowing users to see exactly how much power they have consumed. This can then be compared to the main bill generated by the discom, and each flat, tenant, shop, office, floor, or department pays for only those units that they consumed.

Let’s check out how this entire process of sub metering works step by step:

• Step 1 – Main meter is installed on a property: The electricity board installs a main meter at the entry point of the building. This meter records the total power used by the whole property.
• Step 2 – Power distribution begins: From the main meter, electricity flows into the building’s distribution board (DB). The DB splits the supply into separate lines for each flat, shop, office, or floor.
• Step 3 – The electric sub meter is installed: A sub meter is installed on each outgoing line. For example, one for Flat A, one for Flat B, and one for the lift. Each sub meter only records usage for its own line.
• Step 4 – The electric sub meter takes the readings: Smart sub meters automatically send readings to your phone or computer.
• Step 5 – Consumption is calculated: For each sub meter, subtract last month’s reading from this month’s reading. The result shows exactly how much electricity the flat, shop, or office uses.
• Step 6 – Bill is split fairly: Multiply the units consumed by the electricity tariff. Add fixed charges if needed. If the main meter shows more units than the sum of all sub meters, the difference represents common area usage, such as lifts and hallway lights. Split that fairly among everyone.
• Step 7 – Bill is shared: Give each tenant or department their share based on their sub meter reading, plus their part of the common area bill.
• Step 8 – Monitoring consumption to save on energy bills: Sub meters make people more aware of how much power they use and when. Tenants can cut down on waste, shift heavy usage to off-peak hours, and even plan to install a rooftop on-grid solar system if they want to reduce bills further.

How is the Sub Meter Bill Calculated?

To calculate the sub meter bill, start by noting the actual usage from each meter. The property’s electricity rate is then applied to work out each person’s bill. Owners should also add admin charges and share common area costs fairly among all users.

Let’s check out step-by-step how you can calculate the sub meter bill for your tenants:

• Step 1 –  Note the readings: Write down each sub meter’s current reading and last month’s reading.
• Step 2 – Find the units used: Units used = current reading − last month’s reading (in kWh).
• Step 3 – Apply the per-unit rate: Bill for the month = units used × per-unit price (your tariff). If your area uses slab rates, apply the slabs in order (lower slab first, then the next).
• Step 4 – Add fixed charges (if any): Some societies add a small fixed amount per space (e.g., meter rent or maintenance). Add it here.
• Step 5 – Add taxes/fees (if any): If your bill format includes electricity duty, GST, or other small fees, add them now.
• Step 6 – Handle common area expenses: Common area units = main meter units − sum of all sub meter units. Split this equally by flat size or by agreed rule, and add each person’s share.
• Step 7 – Share the final amount: Final bill for a space = energy charge (Step 3) + fixed charges (Step 4) + taxes/fees (Step 5) + common area share (Step 6).

Sub Meter Bill Calculation Example

We’ve taken an example of a sub meter bill calculation for a 4-unit apartment building that shows how sub metering helps in fair billing.

Sample Building Data:

• Total building bill: Rs. 12,000
• Average rate: Rs. 8.57 per kWh
• Administrative fee: Rs. 150 per unit
• Total building consumption: 1,400 kWh
• Common area usage: 500 kWh

Here’s how sub metering will help split the bill fairly:

Here’s the calculation breakdown:

• Total individual costs: Rs. 7,714
• Total common area costs: Rs. 3,428 (Rs. 857 × 4 units)
• Total admin fees: Rs. 600 (Rs. 150 × 4 units)
• Grand total collected: Rs. 11,742
• Master bill amount: Rs. 12,000
• Difference: Rs. 258 (covers billing service provider fee)

Who Can Install Sub Meters?

Commercial property owners, industrial facilities, and individual homeowners, each with specific purposes for implementation, can install electric sub meters. Housing societies install sub metering to ensure fair utility billing among residents and eliminate disputes over shared costs. Commercial property owners use sub meters to charge tenants based on actual consumption, while industries use them to monitor equipment efficiency.

Let’s understand the reasons why different stakeholders install sub meters in the first place:

• Housing societies and apartment complexes: They install electric sub meters to allocate utility costs fairly among residents based on actual consumption.
• Commercial property owners: They use sub metering to charge office tenants, retail spaces, and warehouse users based on their specific usage.
• Industrial facilities and factories: They use sub meters to monitor production line efficiency, track departmental consumption, and identify processes that consume the most energy.
• Individual homeowners: They install electric sub meters for ADU billing, electric vehicle charging monitoring, and tracking home business utility expenses.
• Educational institutions: They use sub meters to monitor dormitory consumption, departmental usage, and promote conservation awareness among students.
• Healthcare facilities: They use sub metering to track department-wise consumption and optimize energy usage in critical care areas

What Are the Benefits of Sub Metering?

The main benefits of sub metering include fair cost allocation, energy conservation, and improved property management through detailed consumption insights. Property owners can charge tenants based on actual usage rather than estimates, while tenants gain direct control over their utility costs. 

Let’s check out how installing electric sub meters benefits users:

• Fair billing and cost allocation: This eliminates disputes by charging based on actual consumption rather than estimated splits.
• Energy conservation incentives: When users find out peak hours and the fact that discoms charge more per electricity unit during those hours, they can shift their consumption to non-peak hours easily. This reduces their bills and also protects the grid from overloading.
• Maintenance issue detection: Electric sub meters identify risk of leaks, electrical problems, and equipment inefficiencies early on.
• Billing transparency: There’s a clear understanding of charges and rate structures, which promotes transparency and reduces conflicts.

What Are the Disadvantages of a Sub Meter?

Higher upfront investment, ongoing maintenance expenses, and potential privacy concerns from detailed usage monitoring are a few limitations of electric sub meters. 

Let’s check out all the major disadvantages of sub meters in detail:

• Higher upfront investment: Buying and installing many sub meters can get expensive.
• Ongoing maintenance costs: You might have to keep paying for calibration, software/app plans, and repairs every year.
• Installation complexity: May require significant electrical panel upgrades and modifications in older buildings.
• Privacy concerns: Detailed meter data can show when people are home and how they use electricity.
• Administrative overhead: Someone has to read meters, make bills, handle questions, and sort out issues.
• Billing dispute potential: If readings seem wrong or rates aren’t clear, tenants may complain.
• Tenant resistance: Some residents prefer simplified billing arrangements and may oppose sub metering implementation.

What is the Cost of a Sub Meter for Electricity? 

The sub meter price in India in 2025 can range from ~Rs. 1,000* for a single-phase sub meter to ~Rs. 5,000* for a three-phase sub meter. However, this is just an estimated cost range based on standard market rates from premium manufacturers. The actual cost can be much lower or much higher based on the brand you’re choosing. 

*Please note: The sub meter price listed above is indicative, and not fixed. The actual sub meter price in India can significantly vary from the given range based on the brand, manufacturer’s discount, and the product warranty. Besides, these are just the meter prices. Installation costs and charges of electricians are not included in this price range. SolarSquare does not promote any electric sub meter brand. We install on-grid rooftop solar for housing societies, homes, and commercial complexes. 

How Can On-Grid Rooftop Solar Systems Reduce Electricity Bills by 90% or More?

On-grid rooftop solar systems for homes reduce power bills by 90% or more because the solar panels in the solar system generate free solar electricity for 25+ years. When a rooftop solar system is sized correctly, it can take care of all your energy requirements, reducing your reliance on expensive grid electricity. The result? Bills dropped by 90%, and in many cases, customers eventually get zero bills after going solar.

But is a 90% bill reduction the only reason to invest in on-grid rooftop solar systems? Actually, no. There are many other reasons why on-grid solar is better than off-grid solar systems and hybrid solar systems: 

• The government offers a subsidy: Homeowners and housing societies installing on-grid rooftop solar systems receive a government subsidy under the PM Surya Ghar Muft Bijli Yojana. Keep in mind that this subsidy is offered only for residential installations. You won’t get this assistance for installing commercial rooftop systems.
• They’re the most economical rooftop solar option: Off-grid and hybrid solar systems are expensive because they include lithium batteries for solar energy storage, and batteries are expensive. On-grid solar, on the other hand, sends excess energy generated by the panels to the grid through the solar net metering process. Since batteries are not required, on-grid solar is a lot more economical than off-grid and hybrid systems.

Now, let’s take you through the cost of installing an on-grid rooftop solar system in a city like Nagpur vs the savings you’ll get from the system in 25 years:

*Please note: The above-mentioned solar panel price is indicative as of 11th September 2025 for the SolarSquare Blue 6ft variant. The final cost of installing an on-grid rooftop solar panel system at home depends on your DISCOM charges, product variant opted for, panel type, inverter type, mounting structure height, type of after-sales service, savings guarantee, roof height, etc. Prices are subject to change. Additionally, while calculating savings, we have considered the annual tariff escalation at 3% and the annual degradation at 1%. The actual final savings from solar panel installation depend on the types of solar panels you’ve installed and their efficiency, intensity of sunlight your rooftop receives, orientation of the panels and tilt angle, the pollution level and weather conditions in your city, the temperature, shadow on the roof, impact of dirt/dust, and how well you maintain your panels after installation.

You can also use SolarSquare’s free solar roof calculator to get an estimate of the solar installation cost vs savings in your city!

For housing societies, here’s a simple snapshot of estimated installation cost vs solar savings the system will offer in 25 years of its life:

*Please note: The above-mentioned solar panel price for rooftop solar systems at housing societies in India for DCR projects is indicative as of 11th September 2025 for the SolarSquare’s Blue 4-8ft variant. The final solar system installation cost depends on your DISCOM charges, product variant opted for, panel type, inverter type, mounting structure height, type of after-sales service, savings guarantee, roof height, number of floors in your society, etc. Additionally, we’ve considered the annual plant degradation rate of 0.55% after the first year, an annual tariff hike of 2%, an electricity tariff of Rs. 21 per unit, and an insurance cost of 0.20% to calculate the lifetime savings from an on-grid rooftop solar panel system for housing societies. 

For any further enquiries about installing rooftop solar in your place, you can book a free solar consultation call with SolarSquare today.

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Conclusion

Sub metering is the installation of individual small meters that measure specific utility consumption within distinct areas of a larger property. They provide detailed usage data for individual consumers, such as flats or tenants in a property, unlike the main meter, which shows the power consumption of the entire building. 

Using an electric submeter can help with fair cost allocation, as consumers only pay for the electricity they actually use. Plus, since modern sub meters can also show the peak usage hours, consumers can shift their consumption to non-peak hours, which can eventually reduce their bills because electricity rates in non-peak hours are lower than those for peak hours.

FAQs

Q1. Is a sub meter legal in India?

Ans. Yes. You can install sub meters inside your property to measure each flat/tenant’s usage and split costs. What you can’t do is act like a power distributor or resell electricity as a business without a license.

Q2. What is the lifespan of a sub meter?

Ans. A Sub meter can last from 5 to 20 years, depending on the brand, model, internal component quality, and environmental conditions.

Q3. Does the sub meter have a separate bill?

Ans. No. The utility company generates only one bill, which is based on the power consumption of the entire property as recorded by the main meter. The owner/society uses sub meter readings to split the bill among flats/shops.

Q4. Can you reset a sub meter?

Ans. No, it’s not legal to fiddle with the meter’s reading. Trying to alter or interfere with a meter is treated as tampering and is illegal in India.