District-heating emissions used for GEG proofs are calculated with AGFW FW 309-1 via the Stromgutschriftmethode. In simple terms, electricity from CHP is credited as if it displaced grid power using a fixed “Verdrängungsstrommix” of 2.8 PEF and 860 g CO2e/kWhel. That credit is so large that the emissions left for the heat product can collapse toward zero.
This is why the “official” emissions of many district-heating networks are unrealistically low — sometimes near zero.
The problem: Stromgutschrift (electricity-credit)
The GEG/AGFW practice (FW 309-1) credits CHP-generated electricity at a fixed displacement mix of 860 g CO2e/kWhel and PEF 2.8 (anchored in GEG Annexes 4 and 9). The credit is subtracted from the total plant emissions before allocating to the heat product. Because the credit is based on outdated, coal-heavy grid assumptions, it massively overstates the “avoided” emissions — leaving heat with an artificially clean factor.
Real-world examples confirm the distortion. A public certificate from Potsdam (TÜV-Nord) shows the same network at 0 g CO2/kWhth under FW 309-1 vs. 142 g CO2/kWhth under FW 309-6 (Carnot). A certificate from Bad Elster explicitly lists Verdrängungsstrommix = 860 g/kWhel and shows fCO2eq = 0 g/kWhth.
The alternative: Carnot / exergetic allocation (FW 309-6)
A more physically honest allocation for CHP is the Carnot (exergetic) method (AGFW FW 309-6), which assigns emissions to power and heat according to their thermodynamic quality (exergy/temperature) instead of crediting electricity at a fixed grid factor. When applied, heat receives a larger — and more realistic — share of emissions.
For generic, Germany-wide work where operators do not provide Carnot values, ÖKOBAUDAT offers a transparent fallback: Fernwärme-Mix (DE) with GWP ≈ 0.261 kg CO2e/kWhth. A comparative review by FfE documents how crediting methods make heat look unusually “clean” compared with Carnot and other allocations.
Regulatory outlook
There has been a policy push to move primary-energy factors — and thus emissions — toward Carnot in GEG updates. In practice, current GEG proofs still rely on FW 309-1 (Stromgutschrift); always check the latest legal status for the specific project and certificate year.
What this means in practice
Decarbonisation studies / CRREM-aligned analysis
Use the most realistic value. If the operator provides FW 309-6 (Carnot), use it. If not, use the ÖKOBAUDAT Fernwärme-Mix (~0.261 kg CO2e/kWhth) as a transparent, defensible proxy.
GEG / EH / KfW compliance
You are obliged to use the operator's AGFW FW 309-1 factor (Stromgutschrift). This is compliant but underestimates the real-world carbon intensity of delivered heat. State clearly in reports that it is used because it is mandated.
For strategy and credibility, cite Carnot (or ÖKOBAUDAT if Carnot is unavailable). For GEG paperwork, state clearly that FW 309-1 is used only because it is mandated — and that it drives artificially low heat factors.
Sources
- BDEW “Grundlagenpapier Primärenergiefaktoren” — PEF 2.8, 860 g displacement mix
- AGFW overview — FW 309-1, FW 309-6, FW 309-7 series
- ÖKOBAUDAT Fernwärme Mix (DE) — GWP 0.261 kg CO2e/kWhth
- FfE, Allokationsmethoden CO₂-Emissionen von KWK-Anlagen (2022)
- AMEV “Klimaneutrales Bauen” — confirms 860 g/kWh displacement factor