How Not to Count Carbon: Exposing the Flaws in GSHP Emission Assessments

In our previous post on embodied vs lifetime carbon, we made one thing clear: if you're only counting what happens before a system is switched on, you're missing the real story.

Ground source heat pumps (GSHPs) are often penalised in carbon assessments that overvalue upfront emissions and ignore what matters most: how the system performs over decades. But there's another layer to this problem: bad data IN means bad decisions OUT. And too often, GSHPs are misrepresented from the start.

When Embodied Carbon Gets it Wrong

Embodied carbon figures are easy to misuse or misunderstand. Whether through flawed assumptions or simple lack of technical understanding, it's possible to make GSHPs look far worse than they are. We've seen it all:

• Assuming 100% glycol in ground loops (instead of typical 20–25%)
• Overestimating borehole diameters, depths, or total ground loop lengths using crude rules of thumb
• Including steel casing as a permanent material in the ground (when it's nearly always removed)
• Treating plant replacements as equal across air and ground systems, despite very different lifespans

The result? GSHPs are burdened with carbon they don’t actually emit. And because those numbers feed into models, investment decisions, and design specs, it undermines low-carbon outcomes across the board.

The Power of Good Design

At Genius Energy Lab, we do things differently. We design systems that are efficient and engineered to perform for the long haul.

Here’s what good looks like:

• One system, two functions: By designing for both heating and cooling in one integrated GSHP system, we halve the embodied plant requirement.
• Realistic replacement cycles: GSHPs typically last 25+ years indoors. Air source? Often 12–15 years outdoor… shorter still near the coast.
• Smarter fluid choices: Lower-carbon antifreeze options (or eliminating glycol altogether) are now feasible in many builds.
• Minimal trenching, no excess concrete: We avoid unnecessary grouting or 'mock-away' (excavated material removed from site), reducing waste and transport emissions.
• Precision borehole design: No rules of thumb. Just data, modelling, and decades of drilling experience.

This isn’t about cutting corners: it’s about cutting carbon where you can.

Explore more on the long-term savings and sustainability of GSHPs.

The Rooftop Reality

Urban projects are a perfect case study in overlooked carbon. Air source heat pumps might seem simpler on paper, but in practice:

• They need rooftop steelwork, acoustic enclosures, and extensive ducting
• They take up valuable rooftop real estate: space that could otherwise be used for solar PV, lettable space, or amenity
• They require more maintenance and faster replacement, especially in polluted or corrosive environments

By contrast, ground source systems tuck away quietly at ground or basement level with minimal disruption, and they do both heating and cooling with one set of kit.

In one recent project, a GSHP system cost half that of the proposed ASHP setup once structural steel and rooftop works were accounted for. Embodied carbon followed the same logic.

Dig into a high-rise, space-saving - and award-winning - urban GSHP project. 

Let’s Get Real About Carbon

Carbon accounting isn’t just a technical exercise: it’s a design decision. When clients are pushed toward short-term wins on paper, they risk long-term regret in performance, cost, and compliance.

We believe in carbon integrity: systems that deliver what they promise, for decades.

If you're planning a building, advising a client, or assessing heating options, ask yourself:

• Are we counting the right carbon?
• Are we building for decades, or just ticking boxes today?

At Genius Energy Lab, we’ll help you answer those questions with clarity and confidence.

Want to get under the hood of lifetime carbon?
Book a discovery call with our GSHP specialists or sign up to The Source for monthly insights.

Let’s stop miscounting. Let’s start designing better.

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