“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?