<p>Firewood remains a key energy source worldwide, supporting rural economies and contributing significantly to household heating. However, small-scale firewood enterprises often rely on low-mechanized systems with limited efficiency, high labor demand, and restricted adaptability to uneven terrain. This study evaluated the performance of a novel excavator-mounted firewood processor compared with conventional systems, including separate saw–splitter setups and combined processors. Field trials were conducted using beech and oak logs under two treatments: sorted (18–25&#xa0;cm) and unsorted (8–30&#xa0;cm). Machine performance was assessed in terms of productivity, fuel consumption, energy balance, and processing cost. Results showed that the prototype achieved the highest productivity when processing unsorted logs (1.49 t h^− 1), while for sorted logs its productivity (2.06 t h⁻¹) was comparable to that of the most productive conventional combined system. Labor efficiency was doubled compared to conventional systems, as it required only one operator. Productivity remained stable even on slopes, demonstrating operational flexibility not achievable with standard processors. Although the prototype had the highest hourly fuel consumption (4.18–4.35&#xa0;L h^− 1), its normalized fuel use per ton was comparable to other machines due to superior throughput. Energy balance analysis indicated favorable output–input ratios across all treatments. The prototype operative costs were among the lowest observed (45.1 € t^− 1 for sorted logs), mainly due to reduced labor inputs, with labor costs accounting for 27%, compared to 55–63% for conventional systems. Overall, the excavator-mounted processor offers a valuable solution to enhance productivity and cost efficiency for both flat and moderately sloped terrain. In contrast, conventional systems are generally designed for operation on even terrain. This suggests that the prototype is more adaptable in small-scale firewood supply chains under uneven terrain conditions.</p>