| Item | Baseline | Improved | Saved | Cost Saved (annual) | CO2 Reduced (annual) |
|---|---|---|---|---|---|
| Electricity (kWh) | 18,000 | 13,500 | 4,500 | $630.00 | 1.8000 tCO2e |
| Natural gas (therms) | 900 | 700 | 200 | $250.00 | 1.0600 tCO2e |
| Vehicle fuel (liters) | 2,200 | 1,650 | 550 | $577.50 | 1.2705 tCO2e |
| Total | — | $1,457.50 | 4.1305 tCO2e | ||
- Energy saved = max(0, baseline − improved) for each source.
- CO2 reduced (kg) = energy saved × emission factor (kg per unit).
- CO2 reduced (tCO2e) = CO2 reduced (kg) ÷ 1000.
- Cost savings = energy saved × rate (per unit).
- Carbon value = CO2 reduced (tCO2e) × carbon value per tCO2e.
- Annual net benefit = cost savings + carbon value − annual maintenance.
- Payback = net investment ÷ annual net benefit (when net benefit > 0).
- NPV = −net investment + Σ(annual net benefit ÷ (1 + discount rate)t).
- IRR is the discount rate where NPV equals zero (if solvable).
- Enter baseline and improved annual usage for electricity, gas, and fuel.
- Set your current rates and local emission factors for accurate results.
- Add a carbon value if you monetize emissions reductions or offsets.
- Provide investment cost, incentives, and maintenance to estimate ROI.
- Click Calculate to see results above the form.
- Use Download CSV or Download PDF from the results panel.
Operational savings signal
Annual utility savings come from the delta between baseline and improved activity. For electricity, savings equal (kWh saved × rate). In the example table, 4,500 kWh saved at $0.14/kWh yields $630 per year. Gas savings of 200 therms at $1.25 adds $250, and 550 liters of fuel at $1.05 adds $577.50. These totals guide budget planning.
Emission factor sensitivity
CO2 reduction is calculated as activity saved × emission factor. A grid factor of 0.40 kg/kWh turns 4,500 kWh saved into 1.80 tCO2e annually. If your grid is 0.70 kg/kWh, the same kWh savings becomes 3.15 tCO2e. For gas, 5.30 kg/therm converts 200 therms into 1.06 tCO2e, and 2.31 kg/liter converts 550 liters into 1.2705 tCO2e.
Carbon value scenarios
Carbon value equals annual tCO2e reduced × carbon value per ton. At $35/tCO2e, a 4.1305 tCO2e reduction adds $144.57 per year. Setting this field to zero provides a conservative view, while higher internal prices can represent compliance costs, voluntary targets, or supplier scorecards.
Investment decision metrics
Net investment equals upfront cost minus incentives. Annual net benefit equals energy savings plus carbon value minus maintenance. Simple payback is net investment divided by annual net benefit, when positive. With $8,500 cost, $500 incentives, and $120 maintenance, the example’s net investment is $8,000. If annual net benefit is $1,482.07, payback is about 5.40 years. NPV discounts annual net benefit over the analysis period, and IRR estimates the rate that drives NPV to zero.
Reporting and audit trail
Use consistent periods, meters, and fuel logs. Keep units aligned: gas can be entered as therms, m³, or gas kWh, while emissions are standardized internally. Document the emission factors used and refresh them when tariffs or grid mixes change. A 10-year horizon with a 7% discount rate emphasizes near-term benefits. Export CSV for review and PDF for stakeholders.
What does tCO2e mean in the results?
tCO2e is metric tons of carbon dioxide equivalent. The calculator converts kilograms of CO2 to tons by dividing by 1,000, then sums electricity, gas, fuel, and any extra reductions for an annual total.
Can I use the tool for monthly data?
Yes. Convert monthly readings to annual totals by multiplying by 12, or run each month separately and sum your exports. Keep the same units and emission factors across periods for consistent reporting.
Why is my payback shown as N/A?
Payback is only shown when annual net benefit is positive and net investment is greater than zero. If maintenance exceeds savings, or your improved usage is higher than baseline, payback will not be meaningful.
How should I choose an electricity emission factor?
Use the factor published by your utility, grid operator, or sustainability report. If you have a contract-specific factor, enter that value. Updating the factor is the fastest way to reflect cleaner grids over time.
Does the calculator include upstream emissions?
By default it uses direct, commonly used factors for electricity and combustion. If you want upstream or lifecycle impacts, adjust the emission factors to your preferred methodology and document the source in your reporting.
What is a good carbon value to enter?
Use your organization’s internal carbon price, the compliance price you face, or a proxy based on verified offset costs. Sensitivity test multiple values to understand how climate value influences NPV and payback.