How to Calculate Your Scope 1 and Scope 2 Emissions Without Hiring a Consultant
Singapore's SGX climate reporting rules are now in effect for large listed companies, and the wave is moving toward SMEs. If you have been delaying your Scope 1 and Scope 2 calculation because you assumed it required a sustainability consultant, you can stop delaying. The GHG Protocol methodology is publicly documented, the emission factors are published by government agencies, and the maths is simpler than a tax return. What separates companies that sail through assurance from those that scramble is not sophistication — it is evidence. This guide walks you through the six steps to calculate your emissions correctly, traceably, and audit-ready from day one.
You Don't Need a Consulting Firm for This
The sustainability consulting industry sometimes implies that carbon accounting is an arcane discipline requiring specialist credentials. That impression is, charitably, overstated. The GHG Protocol Corporate Accounting and Reporting Standard — the global foundation for Scope 1 and 2 measurement — is a free, 116-page document published by the World Resources Institute. ISO 14064-1 formalises the same methodology in a standards framework. Both are designed to be implemented by trained internal staff, not just certified consultants.
What a good sustainability consultant genuinely adds is quality assurance: catching errors in your methodology, reviewing emission factor selections, and stress-testing your documentation before an assurer does. That review function is valuable. But the calculation itself — collecting bills, applying factors, computing CO2e — is absolutely something your sustainability manager, finance team, or a well-briefed operations person can do.
Modern AI tools now handle the extraction step: uploading a utility bill and having the system read the kWh figure, the billing period, and the facility address. What AI cannot replace — and what regulators do not expect AI to replace — is the human review gate that confirms the extraction is correct before it enters your accounting records. The combination is powerful: AI for speed, humans for accountability.
The six steps below follow the GHG Protocol structure and are calibrated to the Singapore context.
Step 1: Define Your Organisational and Operational Boundaries
Before you count a single kilowatt-hour, you need to decide what is inside your reporting boundary and what is not. The GHG Protocol offers two approaches for defining the organisational boundary: the equity share approach (include emissions proportional to your financial ownership stake) and the control approach (include emissions from operations you control, regardless of ownership share).
For most Singapore SMEs, the operational control approach is the right choice and the simpler one to implement. The question you ask is: do we have the authority to introduce and implement operating policies at this facility? If yes, include it. If you lease office space but your landlord controls the central cooling and electricity purchase, you do not include the building's common-area electricity in your Scope 2 — that sits with the building owner. You include only the electricity that flows through your own meter and that you are billed for directly.
Ask three questions for each facility or operation: (1) Do we appear on the utility contract or fuel purchase? (2) Do we have the authority to change how energy is used or procured there? (3) Is the operation conducted under our brand and management? Three "yes" answers mean it is inside your boundary. A "no" on contract ownership usually means it belongs to the landlord's boundary, not yours.
Once your organisational boundary is set, define the operational boundary: which emission sources within those operations will you account for? Scope 1 covers direct emissions from sources you own or control. Scope 2 covers indirect emissions from purchased electricity, heat, or cooling. You must report both.
Step 2: Identify Your Emission Sources
With your boundary defined, build a source inventory — a systematic list of every point in your operations where greenhouse gases are emitted. Most Singapore businesses have a shorter list than they expect.
Scope 2 sources (purchased electricity): Your SP Group utility bills. For most office and retail companies in Singapore, electricity is by far the largest emission source — often 80% to 95% of total Scope 1 and 2 footprint.
Scope 1 sources (direct emissions): Company vehicles (diesel, petrol, or CNG combustion in engines you own or lease); refrigerant top-ups to air-conditioning and cold-room systems (refrigerant gases are potent greenhouse gases — HFCs have GWP values in the thousands); on-site diesel generators; cooking gas (LPG or piped town gas) if you operate in F&B.
To illustrate how this varies by industry: an office-based professional services firm may have only one Scope 1 source (a single company car) and one Scope 2 source (office electricity). A food and beverage operator with a central kitchen will add cooking gas, refrigerant top-ups across multiple cold rooms, and potentially a delivery fleet. A logistics company may have a large vehicle fleet (Scope 1) with relatively modest office electricity (Scope 2). The source inventory is always company-specific — do not use another company's list as a shortcut.
Step 3: Collect Your Activity Data
Activity data is the measured quantity of each emission source over your reporting period — typically a calendar year or financial year. The source document for each activity data point is what your assurer will ultimately want to see.
Electricity (Scope 2): Your SP Group monthly bills, showing kWh consumed per meter per period. If you have multiple meters across multiple premises, collect bills for all of them. Gaps in bills (e.g., a meter was sub-metered by a landlord for part of the year) need to be noted and addressed.
Vehicle fuel (Scope 1): Petrol or diesel purchase receipts, fuel card statements, or fleet management system exports. The key figure is litres purchased and consumed, not kilometres driven (though kilometres can be used with a fuel economy conversion if direct fuel data is unavailable).
Refrigerant top-ups (Scope 1): Invoices from your air-conditioning maintenance contractor showing the type of refrigerant (e.g., R-410A, R-32, R-22) and the weight added in kilograms. These invoices exist — your contractor issues them. Request them if you have not been keeping copies.
Cooking gas (Scope 1): Gas bills showing cubic metres of town gas or litres/kg of LPG delivered. SP PowerGrid provides town gas bills with consumption quantities.
Every source document should be retained in its original form — not transcribed into a spreadsheet without the original. When an assurer requests evidence, they want to see the bill itself, not your record of what the bill said. Organise documents by reporting year and emission source, and store them for a minimum of five years.
Step 4: Apply Emission Factors
An emission factor is a coefficient that converts your activity data (kWh, litres, kilograms) into a weight of greenhouse gas emissions expressed in tonnes of CO2 equivalent (tCO2e). Applying the right emission factor — from the right source, for the right year — is the most technically consequential step in the process.
Electricity in Singapore: Use the grid average emission factor published annually by the Energy Market Authority (EMA). This reflects the actual carbon intensity of Singapore's electricity mix for that year. As of the 2023 grid average, the factor was approximately 0.4233 kg CO2e per kWh — but you must use the EMA-published factor for your specific reporting year. Assurers will check whether you applied the correct version-year figure, so document which EMA publication you referenced.
Vehicle fuels: The UK Department for Energy Security and Net Zero (DESNZ, formerly DEFRA) publishes annual conversion factors that are widely accepted in Singapore practice and used by major assurance providers. These cover petrol, diesel, CNG, and LPG combustion. Use the factor set for the year closest to your reporting period and document the source.
Refrigerants: Use the Global Warming Potential values from the IPCC Sixth Assessment Report (AR6). Each refrigerant has a specific GWP — for example, R-410A has a GWP of approximately 2,088 under AR6, meaning one kilogram of R-410A leaked is equivalent to 2.088 tonnes of CO2e. Check the specific refrigerant type on your maintenance invoice and apply the matching GWP.
Cooking gas: Town gas and LPG emission factors are available from DESNZ and are stable enough that a one-year lag in the factor set does not introduce material error — but always document which source you used.
Step 5: Calculate and Document
The calculation itself is straightforward:
Activity Data × Emission Factor = CO2e
For a small professional services office in Singapore with one leased car and no on-site equipment, the calculation might look like this:
Scope 2 — electricity: 120,000 kWh consumed (annual total from SP Group bills) × 0.4233 kg CO2e/kWh = 50,796 kg CO2e = 50.8 tCO2e.
Scope 1 — company car: 3,200 litres of petrol consumed (annual from fuel receipts) × 2.31 kg CO2e/litre (DESNZ petrol factor) = 7,392 kg CO2e = 7.4 tCO2e.
Total Scope 1 + Scope 2: 58.2 tCO2e for the year.
What matters as much as the number is the documentation. Every calculation should have a clear trail: the source document it draws from, the emission factor applied and its source, the arithmetic, and the human reviewer who approved the entry. This is not bureaucracy for its own sake — it is precisely what an assurance provider will reconstruct when they audit your figures. A calculation that cannot be traced back to its source document is effectively unverifiable, which means it will receive a qualified assurance opinion at best.
Step 6: Quality Check and Set Your Base Year
Before finalising your figures, run through a structured quality check. Look for: missing meters (did every facility contribute data?), period mismatches (are all bills covering the same 12-month window?), emission factor version errors (did you accidentally use last year's EMA factor?), unit confusion (is everything consistently in kWh, not MJ or MWh mixed in?), and refrigerant gaps (many companies forget to collect these until the last minute).
Your base year is the reference point against which all future progress is measured. Choose a year for which you have complete, verifiable data. For most companies beginning their reporting journey in 2025 or 2026, the base year will be either FY2024 or FY2025 — whichever has the most complete documentation. Once set, do not change your base year without a documented justification (e.g., a major structural change like an acquisition or divestiture). Year-on-year comparability is what makes your emissions data meaningful to investors, customers, and regulators.
Common errors found in first-year calculations: applying the wrong country's electricity emission factor (Singapore's is lower than the global average but higher than some EU grids — always use the EMA figure, not a generic Asian average); double-counting a facility that is shared with another entity; omitting refrigerant emissions because they seemed "small" (in a cold storage or supermarket context they can be material); and failing to annualise partial-year data correctly for a facility that opened or closed mid-year.
Self-calculation is fully appropriate for Scope 1 and 2. Where external expertise adds clear value: your first year (to review your methodology and source inventory before you lock in a base year); preparing for formal assurance (a pre-assurance gap review is far cheaper than a qualified audit opinion); and Scope 3 boundary-setting (supply chain emissions involve judgement calls that benefit from external benchmarking). The calculation work, year over year, is yours to own.
Frequently Asked Questions
Skip the Spreadsheet Chaos — Build an Audit-Ready Evidence Trail Automatically
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