Water, Energy, and Emissions: Why Your Building’s Water Waste Is a Carbon Problem Too

The water your building wastes has a carbon footprint too.

Zero Emissions Day, observed on September 21, is a reminder to think beyond fossil fuels and ask where emissions are embedded in everyday operations. For a commercial building, one of the less visible answers may be flowing through the plumbing. Every litre of water supplied to a building has already required energy. It may have been extracted from a river, reservoir or groundwater source, pumped across distances, treated, stored and distributed. Once used, it may require pumping, treatment and disposal again. So when a building wastes water, it is not only wasting water. It is also wasting the energy that moved, treated and managed that water. That makes water efficiency more than a conservation issue. It is also an energy-management and emissions issue. And for companies working on BRSR, Scope 2 accounting, net-zero roadmaps and operational efficiency, that connection deserves much more attention.

Water has an energy bill before it reaches your building

Water and energy are often managed by different teams. The facility team may track kilolitres. The energy team tracks electricity. The ESG team tracks emissions .Finance tracks operating costs. But physically, these systems are connected. Water cannot appear at a building’s tap without infrastructure behind it. Pumps, treatment plants, distribution networks, sewage pumping and wastewater treatment all consume energy. Research on Indian cities has already demonstrated this relationship. A study of water and wastewater infrastructure across Indian cities found that these systems contributed between 3% and 16% of community-wide electricity use and greenhouse-gas emissions in 16 cities studied. The study reported average end-use energy intensity of approximately 0.3 Wh/L for drinking-water supply and 0.1 Wh/L for wastewater treatment in the sampled Indian systems.

More recent analysis by the Indian Institute for Human Settlements, drawing on Central Electricity Authority data, estimates that electricity consumption associated with water works and sewage pumping in India averaged about 1,130 kWh per million litres, equivalent to approximately 1.13 kWh per kilolitre, in 2021. The report also shows substantial variation between states, with specific energy consumption ranging from below 0.5 kWh/kL to more than 4 kWh/kL in different contexts. That variation matters. There is no single universal “carbon cost of a kilolitre of water. The actual footprint depends on the source, pumping distance, elevation, treatment requirements, distribution losses, wastewater infrastructure and electricity mix. More water moved and treated means more energy consumed somewhere in the system.

The Hidden carbon inside a flush

Consider something as ordinary as a urinal flush. A person uses a urinal for a few seconds. The flush happens.T he water disappears. Operationally, it feels like a tiny event. But multiply that event across hundreds of users, dozens of fixtures and 365 days. Now it becomes a waterdemand. And that water demand carries an energy requirement. A conventional flush urinal can use water every time it is flushed. A waterless urinal eliminates the flushing water altogether. For example, if one waterless urinal avoids approximately 1.5 lakh litres of water use per year, ten urinals could avoid approximately 15 lakh litres, or 1,500 kL, annually. Using the illustrative Indian water-and-sewage pumping figure of 1.13 kWh/kL, that avoided volume corresponds to approximately: 1,500 kL × 1.13 kWh/kL = 1,695 kWh of energy. For an emissions illustration, the latest publicly reported CEA-linked grid factor for FY2024-25 is around 0.71 kg CO₂/kWh.

That gives:1,695 kWh × 0.71 kg CO₂/kWh = approximately 1.2 tonnes of CO₂. So the water-saving benefit of those ten urinals can also be expressed as an illustrative avoided electricity-associated footprint of roughly 1.2 tCO₂. That is not a universal carbon-saving figure. It is a calculation based on specific assumptions. The actual result should use the building's water source, utility-specific energy intensity and the applicable emissions factor. That distinction is important for serious ESG reporting. But it demonstrates something worth paying attention to: A water-saving project can also be an energy and emissions project.

Your STP has a carbon footprint too

The other side of the building's water cycle is wastewater. Once water leaves the building, the story does not end. It enters drainage networks, pumping systems and treatment infrastructure. At the building level, wastewater may pass through an STP before being discharged or reused. An STP needs energy. Depending on the technology, capacity, treatment quality, aeration requirements, pumping arrangement and operating conditions, energy consumption can vary substantially. Indian projects demonstrate just how wide this range can be. For example, reported energy requirements for some low-energy biological treatment systems are below 0.1 kWh/kL, while other industrial wastewater-treatment systems can consume several kWh per kilolitre. This is why simply saying “we have an STP” is not enough for an energy or carbon conversation.

A more useful set of questions is:

• How many kilolitres enter the STP every day?

• How much electricity does the STP consume per kilolitre?

• How much water is actually reused?

• How much treated water is discharged?

• How much sludge is generated?

• How much pumping is required?

• Is the plant operating close to its design capacity?

• What happens when water quality fluctuates?

The most sustainable kilolitre of wastewater is often the one that does not need to be transported, pumped or treated unnecessarily in the first place.

Water reuse can cut two flows at once

Greywater recycling changes the equation. Instead of treating every litre of incoming freshwater as if it must become potable-quality water and then using it for every application, buildings can increasingly look at fit-for-purpose water. Flushing, gardening, cooling and some cleaning applications do not necessarily require potable water quality. A recycled-water system can therefore reduce the amount of fresh water that needs to be brought into a building while also reducing the volume that needs to leave it as wastewater.

Research on Bengaluru's urban water system found that decentralised recycled-water systems had the potential to reduce the energy intensity of water services compared with parts of the centralised system. The study reported an average energy intensity of 1.8 kWh/kL for centralised water supply and 2.1 kWh/kL for centralised water and wastewater services in its case-study analysis, while decentralised systems showed lower energy intensities in the modelled zones. The lesson for commercial buildings is not that one technology automatically has a lower footprint. It is that the entire water cycle matters. Source. Pump. Treat. Use. Collect. Treat again. Reuse. Discharge. Every stage consumes resources.

Even cleaning chemicals belong in the conversation

Water is not the only hidden input in restroom operations. Chemical cleaning is another part of the operational footprint. Conventional cleaning products can involve raw-material extraction, chemical manufacturing, packaging, transportation, storage, dosing and wastewater impacts. But this is also an area where companies should avoid making simplistic carbon claims. A bio-enzymatic or plant-based cleaner does not automatically have a zero-carbon footprint. To quantify the carbon advantage properly, the comparison should consider: Product quantity × product-specific emissions factor + packaging + transportation + application energy + wastewater implications

“What changes in material use, dosage, packaging, transportation and wastewater when we switch?”For companies building credible ESG data, this distinction matters. A sustainability claim is stronger when it can be traced back to measurable operational changes.

Now calculate the carbon cost of your building's water waste

Here is a simple way to begin. Imagine a commercial building identifies 5,000 kL of avoidable water consumption in one year. This could include avoidable flushing, leaks, inefficient cleaning practices, unnecessary freshwater use for applications that could use recycled water, or other operational losses. Using the illustrative Indian water-and-sewage pumping energy intensity of 1.13 kWh/kL:5,000 kL × 1.13 kWh/kL = 5,650 kWh. Using approximately 0.71 kg CO₂/kWh as the illustrative FY2024-25 Indian grid factor:5,650 × 0.71 = 4,011 kg CO₂. That is approximately:

4.0 tonnes of CO₂ associated with the electricity component represented by that simplified calculation. And this is deliberately conservative in scope. It does not automatically capture every energy or emissions source associated with the water lifecycle.

It does not include:

• Water heating

• Building-level pumping beyond the assumed factor

• On-site STP electricity

• Chemical manufacturing

• Chemical transport

• Infrastructure construction

• Sludge management

• Refrigeration or cooling interactions

• Site-specific electricity factors

• Embodied carbon in water infrastructure

In other words, the calculation is not the building's complete “water carbon footprint.” It is a starting point. And that is exactly where many organisations need to begin.

The missing number in many sustainability dashboards

Most buildings already monitor water consumption. The problem is that water is often treated as a standalone KPI. Water efficiency stops being just a facility-management initiative. It becomes a measurable part of the company's decarbonisation strategyFor a CFO, that can mean lower operating costs. For an ESG team, better environmental performance data. For a facility manager, lower water and energy demand. For a BRSR team, stronger evidence behind sustainability disclosures.

What this means for BRSR reporting

This connection becomes particularly relevant for listed companies. SEBI's BRSR framework asks companies to report environmental information under Principle 6: Businesses should respect and make efforts to protect and restore the environment. The BRSR format includes indicators covering total energy consumption and energy intensity. It also includes water-related disclosures, while BRSR Core includes water footprint, including total water consumption measured in million litres or kilolitres. BRSR is designed around quantitative and standardised ESG disclosures, making data quality increasingly important for companies and their stakeholders. That creates an opportunity for companies to connect operational data instead of managing each metric in isolation. A water-saving project can feed into: Water KPI → Energy KPI → Emissions KPI → Cost KPI

That chain is much more useful than simply reporting “X litres saved.”

And what about Principle 7?

BRSR Principle 7 addresses responsible and transparent engagement when businesses engage in influencing public and regulatory policy. For companies, responsible sustainability advocacy begins with credible internal practice. If a company talks about water resilience, resource efficiency or climate action externally, its own operational data can provide the evidence behind those conversations. That does not mean every organisation needs to publish every internal calculation. It means sustainability claims should increasingly be connected to measurable actions.

Measure the water.

Measure the energy behind the water.

Calculate the associated emissions.

Then report what changed.

Three practical ways buildings can reduce the carbon cost of water

1. Stop using potable water where it is not necessary

Waterless urinals are one example. They remove flushing water from the urinal-use cycle altogether. For buildings with high male occupancy, the annual water volume avoided can be significant. The associated energy and emissions benefit can then be calculated using the site's actual water-energy intensity.

2. Treat wastewater as a resource

An STP should not be viewed only as a compliance asset. Water reuse can reduce freshwater demand and wastewater discharge simultaneously, although the energy required by the treatment and pumping system must be included in the assessment.

3. Measure cleaning beyond litres of water

Cleaning protocols can influence both water and chemical consumption. A more efficient process may reduce:

• Water used per cleaning cycle

• Chemical dosage

• Packaging

• Transport

• Wastewater load

• Cleaning frequency

• Labour-intensive rework

Bio-enzymatic and plant-based cleaning solutions can form part of such a strategy, but the carbon benefit should be calculated using actual product data rather than assumed “green” multipliers. That is how sustainability moves from marketing language to measurable operations.

The real water-energy nexus is inside your operating budget

There is a tendency to think of decarbonisation as a problem solved by solar panels, electric vehicles, energy-efficient HVAC systems and renewable electricity. Those interventions matter. But decarbonisation also happens through thousands of smaller operational decisions. A flush that does not happen. A leak that gets fixed. A kilolitre that does not need to be pumped. A litre of freshwater replaced with appropriately treated recycled water. A cleaning process that uses less water and chemical. A wastewater system that operates efficiently. Individually, these decisions may appear small. Across a large office, hospital, mall, campus, factory or hotel, they can add up. And because water, energy and emissions are physically connected, the business case can be larger than the water bill alone suggests.

Start with one number: kilolitres

The easiest place to begin is your water meter. Take annual water consumption. Then identify avoidable consumption. Separate:

Freshwater consumed

Wastewater generated

Water reused

Water lost

Water saved through projects

Then assign an appropriate energy-intensity factor to the relevant water pathway. Finally, multiply the resulting electricity demand by the applicable grid emissions factor. For more rigorous reporting, replace generic factors with:

• Site-specific electricity data

• Utility-specific water energy data

• Actual STP electricity consumption

• Product-specific chemical data

• Supplier-specific emission factors

• Verified lifecycle assessment data where available

The objective is not to create a perfect number on day one. It is to create a number that becomes more accurate every year.

Water efficiency is no longer just a water story

The next time your sustainability dashboard reports that a building saved one million litres of water. That is the conversation the water-energy nexus brings into the boardroom. Because a building's water waste does not stop at the water meter. It carries an energy cost. And where electricity still carries a carbon intensity, that energy cost becomes an emissions issue too. For CFOs, ESG leaders, sustainability officers and BRSR teams, this creates a practical opportunity:Stop measuring water, energy and carbon as three separate problems. Start measuring the connection between them.