March 28, 2025
Lighting’s Carbon Footprint: A Blind Spot in Sustainability
Inconsistent data causes massive swings in embodied carbon estimates
Architects, engineers, and sustainability consultants rely on whole-building life cycle assessments (WBLCA) to measure a building’s total environmental impact — from construction through demolition. But when it comes to lighting and electrical systems, these tools aren’t telling the whole story.
A recent study published in Energy and Buildings exposes major inconsistencies in how WBLCA software evaluates lighting systems, with estimates of embodied carbon varying by as much as tenfold depending on the tool used. That’s a staggering discrepancy for an industry that prides itself on precision. The research highlights an urgent need for better data, improved software integration, and a standardized approach to assessing lighting’s true carbon footprint.
The Study: A Tale of Two Tools
Researchers at Pacific Northwest National Laboratory (PNNL) tested two of the most widely used WBLCA tools — Tally LCA and One Click LCA — on a Department of Energy office building model. The goal? See how well these programs accounted for lighting’s environmental impact.
The results were anything but reassuring. One tool estimated lighting’s environmental burden to be 20% higher than the other. The biggest culprits? Differences in how each tool calculated energy use over time and how they factored in materials like aluminum, steel, and electronic components in lighting fixtures. One software assumed lighting systems lasted 28 years; the other, just 17. That simple assumption change led to significantly different carbon footprint calculations.
And this is just lighting. If we zoom out to mechanical and electrical (M&E) systems as a whole, the inconsistencies multiply. One Click LCA, for example, is the only major tool that integrates M&E systems at all — but it primarily pulls from European datasets. Tally LCA relies on U.S. data but struggles to accurately model lighting’s operational energy impact.
Why It Matters
If sustainability goals are built on unreliable assessments, are they really goals at all? Lighting is an essential part of any building, yet its carbon impact remains an afterthought in many WBLCA methodologies. This study makes it clear: industry professionals can’t afford to rely on incomplete or inconsistent tools when making carbon-conscious design decisions.
Standardization is the next frontier. Just as the industry has pushed for Environmental Product Declarations (EPDs) to quantify materials’ environmental impact, a similar push is needed for lighting and electrical systems. Without reliable, standardized data, designers and building owners are making decisions based on shaky estimates — potentially over- or underestimating their carbon footprints by double-digit percentages.
The Path Forward
So, what’s next? The study calls for better data integration between building information modeling (BIM) systems and WBLCA tools, a more consistent approach to measuring lighting’s embodied carbon, and a unified methodology for including M&E systems in sustainability assessments.
For lighting manufacturers, the message is clear: it’s time to get ahead of the curve. Providing detailed EPDs, advocating for improved standards, and working with sustainability consultants to refine impact calculations will help ensure lighting isn’t left in the dark in the next wave of green building regulations.
Because right now, lighting’s carbon footprint is either too big, too small, or completely missing from the equation — and without reliable data, sustainability efforts risk missing the mark.
Authors of the Study:
- Kieren McCord – Pacific Northwest National Laboratory
- Taler S. Bixler – Pacific Northwest National Laboratory
- Kasey Johnston – Pacific Northwest National Laboratory
- Trisha Gupta – Pacific Northwest National Laboratory
- Michael Poplawski – Pacific Northwest National Laboratory
- Kate Hickcox – Pacific Northwest National Laboratory
