Wood log + pellet bivalence: securing autonomy for a rural project in Luxembourg
How to size a multicombustible boiler (logs/pellets) for a rural LU project: real autonomy, fuel storage, and what the Klimabonus 2026 actually covers.
Log + pellet bivalence: the right answer for a rural project?
In Luxembourg's rural areas, where gas grids can be thin and wood is often locally available, a log + pellet bivalence gives genuine supply security. Logs cover the bulk of the heating season at near-zero marginal cost when the resource is local ; pellets take over during cold spells, absences, or when the log stock runs out.
One boiler room, two fuels, zero heat interruption — that is the core value of the configuration.
- Logs: lowest €/kWh when locally sourced (~€80-120/stère)
- Pellets: steady availability, automated delivery, more stable €/kWh than fossil fuels
- Split easily adjusted each year based on wood cut and winter severity
What must be locked in at APS?
Three decisions shape the whole project and must be made at the APS stage to avoid cost overruns on site.
- Two separate boilers on a shared hydraulic network = max flexibility, but two flues
- Single multicombustible unit = one flue, smaller footprint, higher capex
- Buffer tank ≥ 1,000 L mandatory for the +15% Klimabonus bonus ; also sized to building inertia
- Pellet silo: ~1.7 m³ per tonne stored, isolated from humidity
- Require EcoDesign (EU 2015/1189) and EN 303-5 Class 5 in the specification
Klimabonus 2026: who actually gets what?
In Luxembourg, only the pellet boiler qualifies for the Klimabonus 2026. The log side, even within a bivalence, is not eligible — a critical point to flag with the client from day one to avoid overpromising.
- Single-family home: up to €8,000 (pellets) ; €4,000 without replacing an old installation
- Apartment building: €6,000/dwelling, cap €40,000
- District heating: €6,000, cap €24,000
- +15% bonus with buffer tank, +€1,000 flat with solar thermal
- Municipal top-ups vary: check aides.klima-agence.lu
Quick checklist to share with the client
A short five-line summary keeps the dialogue with the client on track from APS onward and freezes key decisions before the permit filing.
- On plan: boiler location, silo, buffer tank, log delivery access
- Specify ENplus A1 pellets only in the tender
- Plan chimney sweeping and ash removal (min. 2×/year)
- Check municipal premium on the official simulator before permit filing
- Bake annual maintenance contract into the contractor tender
Sources
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