Heat reclaim from R744 transcritical — the killer feature
By DigiEntropy Engineering · 2026-02-22 · 6 min read
Transcritical CO2 systems reject heat at 60-90 °C — perfect for store heating, DHW, or floor heating. A reclaim-equipped pack covers 80-100 % of winter space heating in temperate climates. Often the dominant economic argument vs R454C centralised.
About this post — Authored by an AI assistant using DigiEntropy's polynomial corpus, the universal compressor predictor, and the project's chart-generation tooling. Charts are produced by Python scripts that read the same database the live site queries; tables and formulas are pulled from the same engineering modules. Findings reflect the project's current dataset and methodology — send corrections or deeper questions to admin@digientropy.com.
The transcritical R744 cycle has a feature that no sub-critical refrigerant can match: it rejects heat across a wide temperature range, starting hot. The gas cooler discharge runs at 60-90 °C; the gas cooler outlet at 30-40 °C. That entire temperature gradient is available as usable heat for store heating, sanitary hot water, or floor heating.
For a typical EU supermarket, the reclaim-able heat from the refrigeration pack covers 80-100 % of winter space heating in temperate climates, and 30-50 % of annual DHW. Often THIS — not the F-Gas regulatory advantage — is the dominant economic argument for R744 vs R454C centralised.
60-90 °C - gas cooler discharge - outlet at 30-40 °C
The gas cooler discharge runs at 60-90 °C; the gas cooler outlet at 30-40 °C. That entire temperature gradient is available as usable heat.
80-100 % - of winter space heating - temperate climates; 30-50 % of annual DHW
For a typical EU supermarket, the reclaim-able heat from the refrigeration pack covers 80-100 % of winter space heating in temperate climates, and 30-50 % of annual DHW.
130 kW - rejected by a 100 kW MT pack - compressor power + cooling load
A 100 kW MT supermarket pack on R744 transcritical rejects roughly 130 kW total (compressor power + cooling load).
2-4 years - reclaim payback - €15-30k capex, €5-10k/year saved
Capital cost of the reclaim package: typically €15-30k for a mid-size supermarket pack. Heating-cost savings: €5-10k/year in a temperate EU climate. Payback: 2-4 years.
250 t - lifetime emissions with reclaim - R454C centralised: 700 t
Lifetime emissions (TEWI): 700 t for R454C centralised, 250 t for R744 transcritical + reclaim. The "+€30k for 70 % lower CO2" trade is increasingly attractive as sustainability mandates tighten.
€6200 - annual saving, Köln example - payback 4 years
Annual saving: €6200. Reclaim capex: €25k. Payback: 4 years.
Where the heat is
A 100 kW MT supermarket pack on R744 transcritical rejects roughly 130 kW total (compressor power + cooling load). Available heat by temperature tier:
Available heat by temperature tier, 100 kW MT pack
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