LEED v5 Energy Modeling: From Cost Savings to Carbon

The U.S. Green Building Council launched LEED v5 in 2025, and it's the most significant rethink of the rating system in years. For anyone involved in energy modeling, one change stands above the rest: LEED is moving from rewarding energy-cost savings to rewarding carbon reduction. Here's what that means in practice.

Decarbonization moves to center stage

LEED v5 is organized around three impact areas — decarbonization, quality of life, and ecological conservation & restoration — with decarbonization carrying the most weight. Across the rating system, roughly half of all points now connect to cutting carbon. Energy & Atmosphere (EA) is where much of that plays out, and it's been substantially reworked.

The new prerequisite: a decarbonization plan

Every LEED v5 project must now produce an Operational Carbon Projection and Decarbonization Plan. In practice this asks the team to:

• Run a design-stage energy analysis
• Establish a site energy estimate
• Produce a carbon (GHG) projection for the building's operation
• Lay out a plan to reduce those emissions over time

That makes energy modeling a required, early-stage activity for every project — not just a tool for chasing optional points.

Cost out, carbon in

Previous versions leaned on energy cost as the headline performance metric. LEED v5 shifts the emphasis to greenhouse-gas emissions, aligning the rating system with global net-zero goals. For modelers, that means reporting results in terms of operational carbon — applying emissions factors to each fuel and reflecting how a grid decarbonizes over time — rather than dollars alone.

Electrification and refrigerants matter more

Because carbon is the currency, electrification becomes a powerful lever: all-electric and heat-pump strategies typically post far lower operational emissions than fossil-fuel systems, especially on a cleaning grid. LEED v5 also sharpens its focus on refrigerant management, enhanced commissioning and on-site/off-site renewables — all of which feed into the modeling and the decarbonization narrative.

Which baseline standard applies?

LEED v5 energy modeling references ANSI/ASHRAE/IES Standard 90.1-2019, with a planned move to 90.1-2022 for projects starting in 2028. (For a refresher on how the 2016 and 2019 editions differ, see our ASHRAE 90.1-2016 vs 2019 article.) Always confirm the exact baseline that applies to your project's registration date.

What it means for project teams

The takeaway: model early, model for carbon. A LEED v5 project benefits most when the energy model informs envelope, systems and electrification decisions at design stage — feeding the decarbonization plan and maximizing EA performance at the same time. Teams still optimizing only for cost will be working against the grain of the new system.

This article is general guidance and reflects information available at the time of writing. LEED v5 requirements are defined by USGBC and may be updated — always confirm current requirements in the official rating system for your project.