The guesswork is over: It’s time for real IT carbon accounting

Thomas Mardahl, CEO and founder of Rejoose, explains why reputations can be built and lost on how a company handles its carbon accounting

In finance, no CFO would ever approve a budget based on the average cost of a single laptop. Or settle for guessing invoices by weight.

But in carbon reporting, this is still common practice.

As carbon disclosure becomes not just mandatory but a competitive and strategic differentiator, the gap between carbon guesswork and carbon accounting is becoming more obvious, and more costly.

The end of guesswork

Call it what it is: carbon guesswork. Whether you're multiplying your IT spend by a carbon factor, or estimating emissions based on average weight — you're guessing. These shortcuts might help fill a spreadsheet, but they don’t support real decision-making or emissions reductions.

Actual carbon accounting, like financial accounting, relies on:

· The real cost of what you purchased

· The actual configuration of what was delivered

· The cumulative impact over time — not just a one-off number

If you’re not using data tied directly to product-level footprints, you are missing the mark.

Spend isn’t carbon

As an example, look at two real-world products purchased at similar prices:

· Laptop A: 14” fanless business device, ultra-efficient CPU — 134 kg CO₂e

· Laptop B: 15.6” performance laptop with discrete GPU — 441 kg CO₂e

On paper, they might cost the same. But in carbon? One is more than three times worse.

Now imagine doing this across 10,000 devices, or for a multi-year procurement cycle. That is not just an error — that is a risk to your carbon targets and your reputation.

Carbon accounting equals strategic visibility

Just like financial reporting is broken down by line items, departments, and time periods — carbon data must be detailed, dynamic, and regular.

Know your carbon cost per purchase; track your footprint monthly or weekly, not just annually; and use this data to change course if you are off track, or double down if you are on the right path. Anything less is just wishful thinking.

Looking ahead, we need to align carbon strategy even closer with financial frameworks and that is where two emerging metrics come in: YCC (Yearly Carbon Cost) – the operational emissions per year from a solution, accounting for energy consumption and usage profile; TCC (Total Carbon Cost) – the full lifecycle footprint including embodied emissions, use phase, and EOL impact.

Together YCC + TCC provide the full truth about the carbon impact of a solution – in the same way CAPEX and OPEX inform total financial cost of ownership.

This approach may still be next-level thinking for many in 2025, but it’s the direction the industry is heading. Procurement teams, sustainability officers, and IT decision-makers will increasingly benchmark products and services not just on specs or price — but on how they perform across time in carbon terms.

When we can calculate, compare, and justify a purchase based on YCC and TCC, carbon becomes a factor in every business decision, not just a number in a report.

Automation is not a ‘nice-to-have’

No organisation can manually track emissions for thousands of IT products and purchases. It is not scalable, and ironically, not sustainable. Automation of carbon data — delivered per SKU, per purchase — is how leaders are freeing up resources to focus on what actually matters: reducing emissions.

This isn’t about ticking boxes for CSRD or climate audits — it is about having the time and clarity to make decisions that matter, before someone else does it for you.

If you are relying on carbon guesswork, you need to ask yourself: would you run your business finances that way? If the answer is no, then now is the time to rethink how you track your emissions.