How to Choose Pellet Burner Output – Selection Guide [2026]

Selecting the right pellet burner output is a key decision before modernising a boiler room. An undersized burner will not heat the system on the coldest days — the boiler will operate at the edge of its capacity and room temperature will drop. An oversized burner constantly runs below its modulation range, resulting in unstable combustion and shorter operating cycles. A well-matched output means thermal comfort, predictable fuel consumption and a longer service life for the entire set. In this article, we show how to select pellet burner output for a single-family home, a commercial installation or an industrial facility based on the PellasX product range.

General rule — burner output vs. boiler output

The basic principle: burner output is selected with a reserve relative to the rated output of the boiler. The rated output of the boiler (per EN 303-5) is the useful output — after accounting for heat exchanger efficiency. The burner must therefore deliver more energy than the boiler transfers to the system: for a 25 kW boiler with 90% efficiency, the burner at maximum operating point should deliver approx. 27.8 kW (25 ÷ 0.9). In practice, this means a burner with a rated output of approx. 110–120% of the boiler output — e.g. REVO EC 30 (9–30 kW) for a 25 kW boiler.

This does not risk “overheating” the boiler: burner output is electronically modulated in the range of 30–100% of rated output, and the working output is set on the controller at commissioning. There are two limits to the reserve: the combustion chamber and heat exchanger must accommodate the flue gas stream (each PellasX model has minimum chamber dimension requirements), and excessive oversizing raises the lower modulation threshold — a burner twice too large will cycle on/off in the transitional season.

When selecting a burner for an existing boiler, combustion chamber dimensions are also taken into account. PellasX burners have specific minimum requirements — for REVO EC these are chambers with a depth of 300–520 mm (depending on output), for ECOS 650–1250 mm, for ECOS Industrial 1400–1500 mm.

Single-family home — REVO EC and REVO

For a typical single-family home, the most common choice is the REVO series. In its technical materials, PellasX provides recommended heated areas for each REVO EC model:

The area values shown are indicative guidelines for buildings of typical energy standard. Actual demand depends on the quality of insulation, ventilation, building orientation and the design temperature for the location. For energy-efficient buildings (new homes with 20+ cm insulation), the same area requires significantly less output than in an uninsulated building.

The REVO line offers four variants dimensionally identical to REVO EC: Revo 10kW (3–10 kW), Revo 16kW (4.8–16 kW), Revo 26kW (7.8–26 kW) and Revo 30kW (9–30 kW). The difference from REVO EC concerns fan technology (hybrid vs. EC BLDC), internal feeder design (standard vs. Internal Feeder with synchronous motor), housing (standard vs. non-combustible ABS) and power consumption during operation (50 W for REVO vs. 67 W for REVO EC).

Dimensions of REVO / REVO EC / REVO EC HG burners (identical across the 3 lines)

All three REVO lines have identical external burner dimensions — they differ only in fan drive technology and electrical system. The four variants 10kW, 16kW, 26kW, 30kW differ only in combustion chamber length (dimension A).

Overall body dimensions (identical for all 4 variants): upper width 285 mm, lower width 266 mm, total height 275 mm, base height 246 mm, mounting spacing 240 mm, mounting hole ⌀35 mm, burn pot ⌀ 129 mm, pellet inlet ⌀ 60 mm, mounting opening ⌀135 mm. Minimum boiler combustion chamber width ≥218 mm, height ≥262 mm.

Wood-gasification boilers — REVO EC HG

In wood-gasification boilers, only REVO EC HG is used — available in the same four output variants as REVO EC (3–10, 4.8–16, 7.8–26, 9–30 kW). The technical parameters are identical to REVO EC, except for chamber underpressure (15 Pa) and power consumption (71 W operation / 371 W ignition).

Commercial facilities — ECOS series

For small hotels, multi-family buildings, offices, schools and production facilities with demand of 15–250 kW, PellasX offers the ECOS line with the Easy Clean-Out system. Seven models cover the entire range:

Each ECOS model has specific requirements regarding the mounting opening (260, 300 or 340 mm square) and chamber underpressure (25–45 Pa). Before purchase, boiler geometry must be verified — an ECOS will not “fit” into a chamber designed for a different burner.

Industry and heating plants — ECOS Industrial and X line

For facilities with demand above 250 kW, two lines are available. ECOS Industrial offers two models: ECOS 350 (105–350 kW, recommended residential area 5,385 m² / industrial 2,917 m²) and ECOS 500 (150–500 kW, 7,692 m² / 4,167 m²). ECOS Industrial uses a Walking Grate — a segmented trough grate with independent section movement, designed for continuous operation with lower-quality pellets.

The X line consists of trough-type burners covering the widest range (5–500 kW). In the industrial segment, the most frequently chosen are X 190 (65–190 kW), X 260 (80–260 kW), X 350 (100–350 kW) and X 500 (120–500 kW). The X line uses positive-pressure combustion technology (forced fan draft), and from X 260 upwards a Lambda Control probe is supplied as standard.

Sizing mistakes — what to avoid

• Sizing based on “similar houses at the neighbour’s” — every building has different demand; differences in insulation and ventilation can double the result.
• Ignoring the modulation range — a burner operates within a range of, e.g., 4.8–16 kW. A house with 3 kW demand in March will keep an EC 16 burner constantly at minimum modulation — EC 10 may be a better choice.
• Sizing for maximum demand — heat-load calculations for -20°C or -25°C apply to only a few days a year. Burner output should cover typical, not extreme, conditions with a reserve.
• Omitting DHW — if the boiler handles domestic hot water, output selection must also account for this load.
• Forgetting about chamber dimensions — even a well-sized burner will not work if it doesn’t fit inside the boiler chamber. Each PellasX model has defined minimum requirements.

Selection support — cooperation with PellasX

PellasX operates in a B2B model — we sell burners through a network of distributors, boiler manufacturers (OEM) and authorised installers. For partners, we provide full technical documentation, output-sizing calculators and engineering support for non-standard projects. If you are working on a specific installation and need help choosing a model, contact our technical department — we will help assess demand, select the burner and refer you to a partner in your region.

Further reading and sources

• Pellet Boiler — Complete 2026 Guide (Types, Classes, Sizing)
• EN 12831-1:2017-08 — Energy performance of buildings. Method for calculation of the design heat load (PKN)
• ASHRAE Handbook — HVAC Applications (heating output sizing)
• ENplus — A1 pellet quality certificate
• EN ISO 17225-2 — quality classification of wood pellets
• Clean Air Programme — terms of co-financing for modernisation