What does the carbon accounting worksheet answer?
The worksheet answers a focused question: what emissions are associated with supplying a defined compressed-air service over a defined period, and how much of any change comes from using less energy rather than from a different emission factor or boundary? It is not a compressor sizing tool, a product life-cycle assessment or a carbon-credit calculation.
Plant teams use the result to:
- Show the share of site electricity used by compressed air.
- Find missing meters and estimated figures that weaken the result.
- Compare like-for-like periods before and after an improvement.
- Allocate compressed-air emissions to departments or products.
- Support a sustainability report with a traceable figure.
A compressor-house subtotal is part of the site inventory, not an addition to it. Never add it to a site electricity total that already includes the same compressors.
Define the boundary first
Draw the boundary around the service you are assessing and list everything inside it. A typical compressed-air boundary includes compressors, dryers, filters with electric drains, cooling-tower fans and pumps serving the compressors, and the compressor-room ventilation fans. It may also include a diesel compressor on hire during a shutdown or a generator supplying the compressor house during power cuts.
| Item | Energy source | Usual record |
|---|---|---|
| Electric compressors | Grid electricity | Feeder energy meter or logged kW |
| Refrigerated or heated desiccant dryers | Grid electricity | Sub-meter or rated power × hours |
| Heatless desiccant dryer | Compressed air (purge) | Purge flow converted to compressor energy |
| Cooling tower and pumps | Grid electricity | Share of utility meter |
| Diesel generator for compressor house | Diesel | Fuel issue log in litres |
| Portable diesel compressor | Diesel | Fuel log and hour meter |
Build a source-by-source energy ledger
Record each source on its own line with the period, quantity, unit and how it was obtained. Mark every value as measured, calculated from logged data, or estimated. Estimates are acceptable if they are labelled; an unexplained precise number is worse than a transparent estimate.
For electricity, the best basis is energy (kWh) from a meter at the compressor feeder. Next best is logged power over a representative period, scaled to the full period with documented running hours. Least reliable is motor rating multiplied by hours, because a compressor rarely draws exactly its nameplate power and unloaded running still uses energy.
For diesel, use fuel issued in litres. Hour-meter readings alone do not give fuel use, because consumption depends heavily on load.
Emission factors and the Indian grid
Every factor used needs its own record: the value, unit, source, publication or version, the year it applies to and which gases it covers. For Indian grid electricity, the Central Electricity Authority publishes a CO2 baseline database for the power sector that is widely used for grid emission factors. Use the edition that matches your reporting year and say so.
Diesel emission factors per litre come from recognised national or international inventory guidance. Record the source and whether the factor is CO2 only or CO2-equivalent including other gases.
Two views of electricity are common in corporate reporting:
- Location-based: uses the average grid factor for where the electricity is consumed.
- Market-based: reflects contracts such as renewable power purchase agreements or certificates.
Report them separately and label which is which. Do not mix a location-based figure for one period with a market-based figure for another.
The core equations
Emissions from each source: E_source = Activity × Factor
Total for the boundary: E_total = Σ E_source (only for sources with compatible boundaries and gas coverage)
Intensity: emissions per unit of useful output, for example kg CO2 per 1,000 m³ of delivered free air, or per tonne of product.
Unit control matters. A factor in t CO2/MWh multiplied by kWh gives a result a thousand times too large unless converted. The worksheet converts every activity to a consistent unit before multiplication and shows the conversion.
Worked example: compressor station over a year
The numbers below are a teaching example only. The emission factor of 0.7 kg CO2/kWh is illustrative and is not an official value for any year.
- Two screw compressors average 160 kW combined over 6,000 operating hours: 160 × 6,000 = 960,000 kWh.
- A refrigerated dryer averages 5 kW over the same hours: 30,000 kWh.
- Station electricity: 990,000 kWh.
- Emissions: 990,000 × 0.7 = 693,000 kg, or 693 t CO2.
- If the station delivered an average of 25 m³/min of free air over those hours, it supplied 25 × 60 × 6,000 = 9,000,000 m³, giving an intensity of about 77 kg CO2 per 1,000 m³.
Now suppose a pressure reduction of 1 bar is made. As a rule of thumb, each bar of extra pressure costs about 7 percent more compressor power, so reducing pressure by 1 bar saves roughly 7 percent of compressor energy: about 67,200 kWh, or about 47 t CO2 at the same factor.
Diesel and generator operation
Many Indian sites run compressors on diesel generators during grid outages, or hire portable diesel compressors for shutdowns and projects. These emissions are direct fuel combustion and belong on their own lines.
For a generator-supplied compressor house, count the diesel burnt by the generator, not the electricity it produced, to avoid double counting. If the generator also serves other loads, allocate its fuel by the share of electrical energy delivered to the compressor house.
For a hired diesel compressor, use the fuel log. On our own hire jobs, machines are serviced every 300 running hours, and the same service records give a reliable hour count to check fuel logs against.
Dryers, purge, leaks and heat recovery
- Heatless desiccant dryers use a significant share of the dried air as purge. That air costs compressor energy; convert the purge flow to kWh using the station’s specific power.
- Leaks consume compressor energy all the time the system is pressurised. A leak survey can estimate the share, and the leak-related emissions follow from it.
- Heat recovery can displace fuel or electricity used elsewhere. Report that as a separate project benefit with its own evidence, not as a reduction of the compressor-house energy itself.
Separate energy improvement from factor change
If the grid factor falls between two years, emissions drop even if the compressors use exactly the same energy. That is not an engineering improvement. The worksheet splits any change into two parts:
| Component | How it is calculated | What it shows |
|---|---|---|
| Energy effect | (New kWh − old kWh) × old factor | Change caused by using more or less energy |
| Factor effect | New kWh × (new factor − old factor) | Change caused by the grid or fuel factor |
| Total change | Sum of both | Reported inventory change |
For an improvement project, normalise for production, operating hours and weather where relevant, so that a quieter year is not credited as a saving.
How Reddy Compressors helps
A carbon figure is only as good as the energy data behind it, and the most effective way to lower it is to make the compressed-air system use less energy. Since 2002 we have supplied, rented and serviced compressors of ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and other makes as an independent multi-brand specialist, from Tarnaka, Secunderabad, with service across Telangana and Andhra Pradesh.
- We carry out air audits including power and flow logging, so your ledger uses measured rather than nameplate data.
- We check specific power, in kW per m³/min, to show whether compressors are performing as they should.
- We find and help repair leaks, review pressure settings and dryer purge.
- We service compressors and dryers and supply new or used machines where a more efficient option makes sense.
What to send us
- Compressor and dryer makes, models and nameplate photos.
- Electricity bills or sub-meter readings for the compressor house, if available.
- Running hours and load hours from each compressor controller.
- Diesel logs for generators or portable compressors serving the air system.
- The reporting period and the emission factors your company uses.
Frequently asked questions
How do you calculate the carbon footprint of a compressed air system?
Measure or estimate the energy the system uses over a period, separated by source: kWh of grid electricity for compressors, dryers and cooling, and litres of diesel for generators or portable machines. Multiply each by its emission factor and add the results. Use metered energy where possible, record each factor’s source and year, and avoid counting the same energy twice.
What emission factor should I use for electricity in India?
Many companies use the grid emission factor from the Central Electricity Authority’s CO2 baseline database for the Indian power sector, choosing the edition that matches the reporting year. Your company’s reporting policy may specify a particular source or a market-based approach for renewable contracts. Whatever you use, record the value, unit, source and year so that the result can be reproduced.
Can I use motor kW rating to estimate compressor energy?
Only as a last resort, and label it as an estimate. A compressor rarely draws exactly its motor rating; it may draw more at full load because of package auxiliaries, and an unloaded screw compressor still draws a significant share of full-load power. Feeder energy meters or logged power over a representative period give a much more reliable basis for carbon accounting.
How much CO2 does reducing compressor pressure save?
As a rule of thumb, each bar of extra discharge pressure costs about 7 percent more compressor power, so a 1 bar reduction saves roughly that share of compressor energy. Multiply the kWh saved by your emission factor for the CO2 figure. Confirm that every user still receives enough pressure, and verify the saving with before-and-after power measurements.
Why did our compressed air emissions fall when nothing changed?
Most likely the emission factor changed. Grid factors are revised as the generation mix changes, so the same kWh can produce a lower figure in a later year. Split the change into an energy effect and a factor effect. Only the energy effect reflects an improvement in the compressed-air system itself; the factor effect should be reported separately.
Should diesel compressor emissions be counted separately?
Yes. Fuel burnt in portable diesel compressors or in generators supplying the compressor house is direct combustion and needs its own line with a diesel emission factor per litre. If a generator supplies the compressors, count its fuel rather than the electricity it produced, and allocate fuel by energy share if it also serves other loads.
Related pages
Calculators and worked examples
These tools give indicative figures for screening, comparison and for preparing an enquiry. They run in your browser and send nothing. No prices or tariffs are assumed: enter your own to see costs. Efficiencies and other figures shown are example values: replace them with your own. Results are not a performance guarantee or a design certificate; final selection is confirmed by a service engineer against the machine data sheet and the site.
Compressed-air station carbon ledger
Turn station electricity and any diesel into CO₂ emissions with your own emission factors, an intensity per 1,000 m³ of delivered air, and the effect of a pressure reduction.
The worked example below shows the method with fixed numbers. Turn on JavaScript to change the inputs.
Worked example
Inputs
- Compressors: average combined input power (kW): 160
- Dryers: average input power (kW): 5
- Other electric auxiliaries in the boundary: average power (kW): 0
- Operating hours per year: 6000
- Grid emission factor, illustrative default (kg CO₂ per kWh): 0.7
- Diesel burnt for the air service (litres per year): 0
- Diesel emission factor (kg CO₂ per litre): 2.68
- Average delivered free air (m³/min): 25
- Planned pressure reduction (bar): 1
- Compressor power saving per bar reduced (%): 7
Result
- Compressor electricity: 9,60,000 kWh per year
- Dryer electricity: 30,000 kWh per year
- Other auxiliaries: 0 kWh per year
- Station electricity: 9,90,000 kWh per year
- Electricity emissions: 693 t CO₂ per year (6,93,000 kg)
- Diesel emissions: 0 t CO₂ per year
- Total for the boundary: 693 t CO₂ per year
- Free air delivered: 90,00,000 m³ per year
- Electricity emission intensity: 77 kg CO₂ per 1,000 m³ of free air
- Energy saved by the pressure reduction: 67,200 kWh per year
- CO₂ avoided by the pressure reduction: 47 t CO₂ per year
Method. Electricity: kWh = average kW × hours for compressors, dryers and other electric auxiliaries inside the boundary; emissions = kWh × grid factor (kg CO₂ per kWh, numerically the same as t CO₂ per MWh). Diesel: litres × diesel factor. Intensity = electricity emissions ÷ (average free air × 60 × hours) × 1,000. Pressure reduction: kWh saved = compressor kWh × bar reduced × saving per bar (rule of thumb about 7% per bar; edit it). The default grid factor of 0.7 is illustrative only, not an official value: use the CEA CO₂ baseline database edition for your reporting year and say whether it is location- or market-based. 2.68 kg CO₂ per litre of diesel is the IPCC 2006 default CO₂-only value at 0.84 kg/L; use your company’s source. Do not add this subtotal to a site total that already includes the same meters.
What to take from it. Measured feeder kWh and a labelled emission factor make the figure traceable; the cheapest tonne of CO₂ to remove is usually a leak or excess pressure.
Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 17 October 2026. How our engineering content is reviewed.
Energy effect versus emission-factor effect
Split a change in compressed-air emissions between two periods into the part caused by using more or less energy and the part caused by a change in the emission factor.
The worked example below shows the method with fixed numbers. Turn on JavaScript to change the inputs.
Worked example
Inputs
- Earlier period: electricity (kWh): 990000
- Earlier period: emission factor (kg CO₂ per kWh): 0.7
- Later period: electricity (kWh): 922800
- Later period: emission factor (kg CO₂ per kWh): 0.68
Result
- Earlier emissions: 693 t CO₂
- Later emissions: 627.5 t CO₂
- Energy effect: -47 t CO₂ (reduction from using less energy)
- Factor effect: -18.5 t CO₂ (from the change in emission factor)
- Total change: -65.5 t CO₂ = -9.5%
Method. Energy effect = (new kWh − old kWh) × old factor. Factor effect = new kWh × (new factor − old factor). The two add up exactly to new emissions − old emissions. Only the energy effect reflects a change in the compressed-air system; report the factor effect separately. Use the same boundary and the same basis (location- or market-based) in both periods. Factors here are illustrative: enter the published values you report against.
What to take from it. If emissions fell but the energy effect is zero or positive, the system did not improve; the grid did.