How to Read a Coffee Roaster Spec Sheet: Capacity, Burner kW & Airflow

Every week someone sends us a competitor’s spec sheet and asks the same question: “Is this machine really the same as yours?” Usually the answer is no — and the difference is hiding in numbers most buyers skim past. After 153 separate inquiries in our chat logs asking for catalogues and parameters, we decided to write the guide we wish every buyer had before comparing quotes.

This is a plain-language walkthrough of coffee roaster specifications: what each line on a spec sheet actually means, which figures are honestly measured, which are quietly optimistic, and the four numbers you should always ask a supplier to confirm in writing. We build these machines in our own factory, so we will also tell you where our own sheets could mislead you if you read them carelessly.

The One Number Everyone Reads Wrong: Rated Capacity

A “6 kg roaster” does not mean the machine roasts 6 kg. It means the drum is dimensioned so that 6 kg of green coffee occupies roughly the correct fill volume — typically 50–65% of drum volume — at a standard bean density.

Three things change that in the real world:

• Bean density. A dense washed Central American at 1,800 m fills less volume per kilo than a low-grown natural. The same drum can take 6 kg of one and feel overloaded with 6 kg of the other.
• Roast level. Beans expand 50–80% in volume during the roast. A drum that is comfortable at charge is crowded at drop.
• Your target cycle time. Rated capacity assumes a 12–15 minute roast. If you want 9-minute profiles, you need more burner per kilo, not more drum.

The honest way to read the line is as a window, not a setting. We publish both ends — and if a supplier only gives you the maximum, ask for the minimum too. A machine that cannot roast below 40% of rated capacity is useless for sample work and small orders. We covered this in depth in our coffee roaster batch size guide.

Batch counts assume a trained operator, between-batch cooling discipline, and no gas supply bottleneck. Treat them as planning figures, not guarantees.

Burner Rating: kW, kcal/h and the Trap of Comparing Different Units

Burner output is where spec sheets stop being comparable. Some factories quote kW, some quote kcal/h, and some quote gas consumption instead of heat output — which are not the same thing, because a burner is never 100% efficient at transferring heat into the drum.

Conversions you can do yourself:

• 1 kW = 860 kcal/h
• 1 kW = 3,412 BTU/h
• 1 kg of LPG ≈ 12.8 kWh of chemical energy

The number that matters for roast control is kW per kilo of rated capacity. Below roughly 2.5 kW/kg, a gas drum roaster will struggle to hold rate-of-rise through the drying phase on a full batch, especially in a cold workshop. Above about 5 kW/kg you are paying for headroom you may never modulate down to.

Electrical Lines: Read Them Before Your Electrician Does

Roughly one in six of our inquiries — 157 messages in our chat archive — is a voltage question. A spec sheet should always state four things together: voltage, phase, frequency and total load. If any one is missing, the sheet is incomplete.

• Voltage alone is not enough. “220 V” can mean single-phase 220 V or three-phase 220 V, and they need different supplies. Ask which.
• Frequency changes fan speed. A fan built for 50 Hz spins about 20% faster on 60 Hz, which shifts airflow and therefore your profiles. Factories should build to your grid, not convert later.
• Gas machines still need power. Drum motor, exhaust fan, cooling fan, control panel and ignition all draw current. A 12 kg gas roaster typically still needs 1.5–3 kW of electrical supply.

Our full breakdown of grids, phases and plugs is in the coffee roaster voltage guide. If you are buying gas, the practical comparison sits in gas vs electric commercial roasters.

Airflow and Exhaust: The Spec That Decides Your Building Work

Exhaust airflow is quoted in m³/h (or CFM; 1 m³/h ≈ 0.59 CFM). Two things make this number misleading.

First, most sheets quote the fan’s free-air rating — what it moves with nothing attached. Once you add six metres of duct, two bends and a cyclone, real delivered flow can drop 25–40%. Second, the number tells you nothing about the static pressure the fan can work against, which is what actually determines whether your run of ductwork will work.

Ask for airflow and the fan’s static pressure rating in Pa. Then hand both to whoever designs your ducting. The requirements by machine size are laid out in our coffee roaster ventilation requirements guide.

Dimensions and Weight: Measure the Door, Not the Room

Buyers check floor area and forget access. Before you sign anything, confirm four measurements against the spec sheet:

1. Crated dimensions, not machine dimensions — the crate is typically 10–20 cm larger in each direction.
2. Crated gross weight, to check your floor loading and whether you need a forklift or pallet truck.
3. Height to the hopper lip, because that is where an operator lifts green coffee to, several times an hour.
4. Service clearance — you need to open the front panel, reach the bearings and pull the chaff drawer.

A 30 kg roaster that fits your floor plan perfectly is still a problem if the crate is wider than your roller shutter.

Control and Instrumentation: What “Automatic” Actually Covers

“Fully automatic” appears on almost every sheet in this industry and means at least four different things. Pin it down:

Probe type and placement matter more than most buyers realise: two machines with identical drums will read 15–20 °C apart if one probe sits in the bean mass and the other in the airstream. That is why a roast profile is not portable between machines without adjustment. On our YS Series, Siemens PLC control and the probe layout are documented so profiles stay repeatable — see why Siemens PLC control matters and the YS Series smart roasters.

The Four Lines We Ask Every Buyer to Get in Writing

If you take nothing else from this guide, request these four confirmations by email or WhatsApp before you pay a deposit. They are the ones that cause disputes:

1. Minimum and maximum batch in kilograms, for the coffee you actually roast.
2. Voltage, phase, frequency and total electrical load — including on gas models.
3. Crated dimensions and gross weight, plus whether the crate is ISPM-15 heat-treated.
4. Exhaust airflow and fan static pressure, plus the chimney stub diameter.

Any factory that hesitates on these is telling you something. Our sales engineers send this block as standard with every quotation, alongside the spec sheet — and if you are still shortlisting suppliers, our guide on how to source a coffee roaster from China covers the vetting steps that go beyond paperwork.

Comparing Two Quotes: A Worked Example

Say you have two 12 kg gas roasters in front of you at similar prices.

Machine A: burner 42 kW, exhaust fan 1,200 m³/h free air, electrical 220 V single phase 2.2 kW, crated 1,900 × 1,500 × 2,050 mm / 690 kg, “PLC control, profile saving”.

Machine B: burner 26 kW, exhaust fan 900 m³/h, electrical “220 V”, crated dimensions not stated, “fully automatic intelligent control”.

Machine A gives 3.5 kW/kg — comfortable. Machine B gives 2.2 kW/kg, which will feel sluggish on a full 12 kg batch of dense beans and will push you toward longer, flatter profiles whether you want them or not. Machine B also omits phase and crate data, which means two open questions your electrician and your freight forwarder will both raise later. The prices being equal, Machine A is the cheaper machine.

Price differences between machines that look similar usually come down to exactly these lines. We break down where the money actually goes in our commercial coffee roaster price guide.

Frequently Asked Questions

What does “capacity” mean on a coffee roaster spec sheet?

It is the green coffee weight that fills the drum to its designed level — normally 50–65% of drum volume — at a typical bean density and a 12–15 minute roast. It is a design reference point, not a fixed batch size. Always ask for the minimum batch as well, since that determines whether you can roast small lots and samples.

How much burner power does a coffee roaster need per kilo?

For gas drum roasters, roughly 2.5–5 kW per kilogram of rated capacity. Below 2.5 kW/kg you will struggle to hold rate-of-rise on full batches, particularly in cold or high-altitude locations. Above 5 kW/kg you are buying headroom you rarely use, though it does help if you plan short, hot profiles.

Why do two roasters with the same capacity have different exhaust airflow figures?

Usually because one factory quotes free-air fan rating and the other quotes flow at a realistic system pressure. Ask both suppliers for airflow in m³/h and static pressure in Pa. Without the pressure figure, the airflow number cannot be used to design ductwork.

Do gas coffee roasters still need an electrical supply?

Yes. The drum motor, exhaust fan, cooling fan, control panel and ignition system all run on electricity. A 12 kg gas roaster typically needs 1.5–3 kW. Any spec sheet for a gas model that omits the electrical line is incomplete — ask for voltage, phase and frequency before you order.

Can I move a roast profile from one machine to another?

Not directly. Probe type and placement, drum mass, airflow and burner modulation all differ, so the same target curve produces a different roast. Expect to re-develop profiles on a new machine, using cupping rather than the old numbers as your reference. Our commissioning guide covers the first weeks in detail.

Get a Quote

Send us the spec sheet you are comparing against and we will annotate it — line by line — against the equivalent machine from our factory, including the four confirmations above. We have been building drum roasters since 1990, in capacities from 100 g sample machines to 300 kg production lines, across the SD Series, YS Series and full roaster range.

Use the inquiry form on our contact page and tell us your capacity, your grid voltage and the beans you roast. Every machine ships with a one-year full-machine warranty.

Send Your Spec Sheet on WhatsApp — +86 184 0771 4607

WhatsApp: +86 184 0771 4607 · Our engineers answer spec questions directly, and video calls to the factory floor are free.

Last updated: August 25, 2026