You've tracked your energy use, you understand the different scopes of emissions, and now you're ready for the next step: turning that data into actionable greenhouse gas (GHG) calculations. Let's walk through this process step by step.
Building blocks of calculation
For most businesses, calculating GHG emissions involves collecting business activity data and pairing it with emission factors. Think of emission factors as conversion tools; they're the ratio between your energy-related business activity and the GHG emissions that result from that activity.
According to the GHG Protocol, organizations estimate their emissions by multiplying activity data by emission factors, coefficients that represent the average GHG emissions per unit of activity, such as per liter of fuel consumed or kilowatt-hour (kWh) of electricity used.
Emission factors are typically expressed in carbon dioxide (CO₂) equivalent (CO₂e), a standardized unit that converts the impact of different GHGs into a common scale based on their global warming potential (GWP) relative to CO₂. This approach, consistent with Intergovernmental Panel on Climate Change (IPCC) methodologies referenced by the GHG Protocol, enables companies to compare and aggregate emissions from all six GHGs using a single unit.
Scope 1 calculations made simple
Let's start with a practical example for scope 1 emissions. Say you're calculating emissions from gas heating in your facilities. You'll need your fuel consumption data, which your utility provider typically gives you in therms (one therm is the energy content of approximately 100 cubic feet [2.83 cubic meters] of natural gas). You would then take the activity data for gas heating, in therms, across all your facilities and the reporting year and multiply by the emission factor for gas heating.
Here's how the calculation works:
- Fuel consumption: 100 therms per month × 12 months × 10 offices = 12,000 therms annually
- Emission factor: Approximately 25 kilograms of CO2e per therm of natural gas
- Total scope 1 emissions: 12,000 × 25 = 300,000 kilograms of CO2e
The same principle applies to all your scope 1 sources: vehicle fuel consumption; propane for equipment; and refrigerant leaks from heating, ventilation, and air-conditioning (HVAC) systems.
Scope 2 is just as straightforward
For scope 2 emissions, we take a similar approach for purchased energy sources, the most common being electricity. Depending on how utilities are handled, you may use the electricity consumption in kWh from your facilities’ invoices, record the meter readings, or receive estimates.
You'll follow the same process to calculate emissions with electricity consumption:
- Electricity consumption: 50 kWh per month × 12 months × 10 offices = 6,000 kWh annually
- Emission factor: Approximately 10 kilograms of CO2e per kWh (this varies by location and grid)
- Total scope 2 emissions: 6,000 × 10 = 60,000 kilograms of CO2e
The key here is to use location-specific emission factors. If you're in the US, you'll want to use the US Environmental Protection Agency’s (EPA) eGrid data. Other countries have their own national bodies that provide these factors, like the Department for Environment, Food and Rural Affairs (Defra) in the United Kingdom, or the International Energy Agency (IEA), a Paris-based intergovernmental organization that provides policy recommendations, data, and analysis on the global energy sector.
Where to find reliable data
Your utility bills are your best friend here. For scope 1, you'll need heating bills (often shown in therms, British thermal units [BTUs], or kWh), AC maintenance records showing refrigerant usage, and vehicle records including distance traveled and fuel consumed.
For scope 2, your electricity invoices will show consumption in kWh, usually provided monthly, quarterly, or annually. If you're in a leased facility, you might need to work with your landlord to obtain this data or estimate based on your square footage.
Creating value
Accurate data-collection processes and emissions calculations create transparency, improve stakeholder relationships, and help identify opportunities for efficiency improvements and cost savings.
The goal isn't perfection from day one but continuous improvement in accuracy and comprehensiveness of your data. Start with what you can measure easily and build from there. As you become more comfortable with the process, you can refine your methods and expand your scope of measurement.
Most importantly, remember that by creating accurate GHG inventories and allocations, you're contributing to global efforts to address climate change. Every organization that improves measurement and reporting helps create the transparency needed for meaningful climate action.
