esg

Carbon Accounting for Energy Modelers: Real Case Study with Surprising Results

Jul 28, 2025



“Which saves more carbon—an air-source heat pump or a premium insulation upgrade?”

If you're an energy modeler, you’ve likely faced this question. The answer might surprise you—and the reason why could shape the future of how you model energy projects. (Note that the conclusion will differ depending on the model and the costs!)

🔍 The Case Study: Medical Office in Climate Zone 4

A client wanted to reduce emissions and applied for a state decarbonization grant. They had a $50,000 budget and needed to choose between:

  • Option A: Upgrade to a 16 SEER / 9.0 HSPF heat pump
  • Option B: Upgrade the roof insulation from R-19 to R-40

The goal? Maximize carbon savings per dollar.

🧮 The Energy Model Told One Story

Using eQUEST, we modeled both ECMs:

  • Heat pump saved ~14,800 kWh/year and ~600 therms
  • Insulation saved ~10,200 kWh/year and ~400 therms

Energy savings winner? The heat pump. But then we looked deeper...

🌍 Carbon Accounting Flipped the Results

We used average utility emissions factors:

  • Electricity: 0.7 kg CO₂e/kWh (mixed coal + gas grid)
  • Natural Gas: 5.3 kg CO₂e/therm

Carbon savings:

  • Heat pump: ~8.3 metric tons CO₂e/year
  • Insulation: ~7.1 metric tons CO₂e/year

But here’s the twist: The insulation cost $18,000 and the heat pump cost $48,000.

Carbon ROI:

  • Heat pump: 0.17 tons CO₂e saved per $1,000 spent
  • Insulation: 0.39 tons CO₂e per $1,000

Winner for grant funding? Insulation. The cheaper ECM delivered nearly 2.3x better carbon ROI.

💡 Why This Matters for Energy Modelers

  • Grants and policies increasingly focus on carbon per dollar, not just energy
  • eQUEST and other modeling tools can be used to calculate carbon ROI directly
  • Knowing how to build carbon-ready models will set you apart in an evolving field

📚 Want to Learn How to Build Models Like This?

If you’re serious about energy modeling and want to analyze both energy and carbon, it starts with setting up a solid building model.

Our most popular eQUEST course teaches you how to build, zone, and assign systems using eQUEST — one of the simplest and fastest free tools available.

➡️ Learn eQUEST Building Set-Up (Course Page)

You'll walk away ready to build models that support both energy savings and carbon reduction strategies — with confidence.

Carbon accounting is the future of energy modeling. Will you be ready?

Carbon ROI: The Metric Every Energy Modeler Needs in Their Toolkit

Jul 28, 2025

Carbon ROI: The Metric Every Energy Modeler Needs in Their Toolkit

Carbon ROI (Return on Investment) is quickly becoming a must-have tool for energy modelers and sustainability consultants. It shifts the conversation from just dollars saved to carbon reduced per dollar spent — and that’s exactly where ESG-focused clients, grant programs, and future codes are heading.

What is Carbon ROI?

Carbon ROI measures how much CO₂e (carbon dioxide equivalent) you eliminate for every $1,000 spent on an energy conservation measure (ECM).

Carbon ROI = (Annual CO₂e Savings in tons ÷ Project Cost in $) × 1,000

It tells you how carbon efficient an ECM is, not just how financially efficient it is. And that’s key for high-performance buildings and decarbonization plans.

Example: Heat Pump vs LED Retrofit

Imagine two projects:

  • Heat pump: Saves 10 tons CO₂e/year, costs $8,000
  • LED upgrade: Saves 4 tons CO₂e/year, costs $2,500

Now calculate:

  • Heat pump ROI = (10 ÷ 8,000) × 1,000 = 1.25 tons CO₂e per $1k
  • LED ROI = (4 ÷ 2,500) × 1,000 = 1.6 tons CO₂e per $1k

Surprisingly, the LED upgrade has higher carbon ROI — even though the heat pump saves more total carbon. That’s the power of this metric: it helps you prioritize per-dollar impact.

Why Energy Modelers Should Care

  • Utility rates vary — CO₂e factors reveal the real impact
  • Funding often favors emissions reductions, not just kWh savings
  • High Carbon ROI can justify ECMs with long paybacks
  • It complements lifecycle cost analysis and aligns with ESG goals

Get the Free Calculator

Want to test this in your next model review or ECM proposal? Download our simple Carbon ROI Calculator (Excel/Sheets) and start comparing measures side by side.

Bonus: It includes emissions factors for electricity, gas, propane, and more — with customizable values by region.

Final Thoughts

Carbon ROI is not a replacement for traditional energy modeling — it's an enhancement that connects energy decisions to climate outcomes. And that’s what clients, building codes, and public funding care about now more than ever.