Most manufacturers recommend that roasters don't use a machine at full capacity. As a general rule, they recommend using about 75% of the listed capacity (depending on the manufacturer) to permit for consistent airflow through the roast.

You may even go down seriously to 50% capacity or lower for sample roasting and profiling starting a coffee roastery. However, doing so will mean you have to regulate the method by which you roast as you have much more space in the drum.

Altogether, this mean's that it's very important to have a balanced approach when deciding on how big your roaster; too large could be just as detrimental as too small. For more insight, and to break down roasters in to a few different size categories, I spoke to Neil Maree from Genio Roasters in Johannesburg, South Africa. Keep reading to learn what he said.

Picking The Right Size Is Important
Neil says that at Genio, clients are often unaware of the facts they should consider when buying a new roaster. “People often request the drastically wrong size, or they ask about the buying price of all of our roasters,” he says. “If you ask me, this points to too little knowledge and understanding about both their target market and their capability to sell.

He says that while people often search for larger roasters as a means of ensuring they have the capability to expand, it's not that simple. “A lot of folks have think they have to go for a large roaster to be able to turn a profit. These folks think that they want a giant machine simply to roast coffee for the local community.

“Ultimately, upscaling your operation is simple, as long as you have a customer for the coffee. To be able to roast 5,000kg of coffee doesn't mean as you are able to sell 5,000kg. Start with selling 1kg, then 100kg, and then 500kg, and etc,” Neil explains. “Often, we find ourselves convincing people to choose smaller machines.

However, this doesn't mean there aren't mistakes among people looking for smaller machines. Neil says: “On the other end, we've got those who think they can buy a 1kg roaster and start a business from it.

“It requires 15 minutes to roast a group on a 1kg roaster, that will sell for maybe US $30. In order to produce a salary as a company owner with this, you'd need to stand behind the machine for the entire day,” he explains. “This leaves you no time and energy to sell! Roasting doesn't equal making money. Selling equals making money.

To illustrate the time cost for using roasters of certain sizes, Neil compiled a couple of models and forecasts for roasters of different skill levels that you'll find here.

Sizes & Categories
For the purposes of this list, we've broken down commercial coffee roasters into six main categories by capacity: sample, small batch, small commercial, medium commercial, large commercial, and extra large commercial.

Sample Roaster (50g to 500g)
Because the name suggests, the main focus of a sample roaster is to gauge samples of a particular coffee before you commit to purchasing large volumes of it.

While you'll find exclusive and high-quality coffee roasted in small batches on sample roasters, they are not alone suited to anyone seeking to start a roastery at a big scale.

There's also lots of overlap between craft and sample roasting as of this range; many home roasters will naturally adhere to a low minimum capacity if they're roasting coffee to solely be enjoyed at home.

Small Batch Roaster (1kg to 3kg)
After sample roasters, the next step up for roasting coffee at almost any commercial scale is a small batch roaster. These range in dimensions from 1kg to around 3kg and are good for sample roasting in larger batches or identifying the proper roast profile for a fresh coffee.

These are a great choice for micro-roasters, as well as successful coffee shops seeking to roast their own beans. Most coffee shops don't sell a lot more than 10kg of coffee per day, but even when they do get close, a 1kg to 3kg roaster will be able to provide that in a matter of hours.

For a café or perhaps a smaller existing coffee business, this is an excellent place to start. By starting small and being strategic about just how much coffee you roast, you can develop a wholesale customer base steadily minus the risky overheads of a more costly roaster.

Neil tells me that this is the prospective market for Genio's smallest machine, the Genio 3 Micro Coffee Roaster, launching in December 2020. “With this particular, we wanted to concentrate on people have been ‘owner-operators '; one or two-person businesses who roast and sell on their own,” he says.

“A 3kg roaster is the backbone of the owner-operated roasting industry.  You've enough capacity to essentially grow with a low enough capital outlay to be accessible to anyone with some savings and an interest for business.”

Small batch roasters likewise have their uses for larger roasteries, however. Many can keep a device of this size on-hand to profile new coffees without wasting large quantities of fresh green coffee. These profiles may then be translated onto larger commercial machines to start roasting at scale.

However, it is also important to notice that your consistency will naturally decrease as you begin roasting a larger amount of batches. For example, roasting 600 batches in a 1kg machine will leave more room for error than, say, roasting 100 batches on a 6kg machine. Keep in mind that too little consistency would have an impact on customer retention.

Small Commercial Roaster (5kg to 15kg)
Commercial non-small batch roasters start at around 5kg. The next phase up from a tiny batch roaster, these machines are more worthy of teams seeking to roast coffee at scale as opposed to small businesses or cafés seeking to diversify.

“A Genio 6 roaster can roast around two tonnes of coffee monthly,” Neil tells me. “That's lots of coffee.” He notes, however, that not surprisingly potential output, smaller-capacity commercial roasters continue to be quite versatile and can still be properly used to roast tiny batches for profiling.

Neil also warns against roasting to a machine's maximum weekly or monthly output. “Roasting two tonnes of coffee on a 6kg machine is similar to driving 5,000 miles every month,” he says. “It is obviously possible, but you'd must have a mechanic regularly carry out a major service in your car.”

Finally, Neil notes that the roaster of this size is a significant investment. For all up-and-coming roasters, he warns that the larger roaster could possibly be bigger than the business needs. “Even if you can roast two tonnes of coffee monthly, you need to consider: who have you been going to sell this coffee to?

Medium Commercial Roaster (15kg to 30kg)
Machines with a group size of around 15kg are most worthy of existing roasting businesses that have a solid base of customers. Many successful specialty coffee roasters will find that this is actually the biggest machine they will ever need.

Neil notes that lots of roasters think it is tempting to sell their preexisting roaster to finance a costly purchase, but warns against it. He says he often sees this when people come to him to purchase larger roasters, including the Genio 15 or the Genio 30.

“Let's say you have a 6kg roaster and you wish to buy a larger roaster. I'd say that you shouldn't sell the 6kg roaster – that will become your backup. Mechanical faults do happen – things break.” At this time, having an established customer base, being left without a roaster could possibly be catastrophic.

Large Commercial Roaster (30kg to 70kg)
Moving after dark 15kg to 30kg bracket will only be necessary when you have an enormous customer base. Roasters of this size are apt to be operating on a big commercial scale.

However, as of this stage, you can find apt to be unforeseen expenses which come along with the purchase of a larger roaster, as Neil explains.

“[With these bigger roasters], people often don't have the proper gas supply or ventilation in place,” he says. “Maybe it's just too difficult to run a chimney from the premises or a fuel main in… as of this size, it's a significant consideration.

“At Genio, we offer pre-inspection through video calls or face-to-face to ensure our larger products can squeeze into your space.”

Beyond ventilation and gas supply, you might also need the actual size of one's space to consider. As many roasters begin a tiny scale and gradually scale up, their premises can often only fit a couple of small machines. As of this stage, it might be essential to relocate.

Extra Large Commercial Roaster (70kg and up)
Beyond 70kg, extra large commercial roasters are generally employed for mass roasted coffee as opposed to high-scoring specialty coffee. Operating a device of this size will require a separate team, and it is going to be used to provide a regular, signature flavour profile on a broad scale as opposed to roasting different single origin lots, for example.

Just like the prior size category, roasters will also have to look at the physical constraints of these space before installing a machine of this size. These roasters will often be present in large open manufacturing spaces, as they might require 50 to 60 square metres of space and often weigh over two tonnes.

Other Points To Consider
Neil tells me that as well as floor space, ventilation, and gas supply, you also need to take into account machine maintenance if you're upgrading to a larger machine. Bigger roasters take more effort to clean and could be more technical to maintain.

Changing how big your roaster may also affect the profiles you have identified for roasting certain coffees. While these existing profiles can still be properly used as a baseline, remember that machines of different sizes will act differently throughout the roast.

Anticipate to need to tweak and change. “You can't truly copy profiles from roaster to the other, although we do head to extensive efforts as manufacturers to use and make that easier,” Neil says.

However, Neil says that the time it takes to attain a particular roast profile shouldn't really change as how big your machine does. “Your roasting technique shouldn't be determined by the machine,” he says. “It should be determined by the flavour profile of the coffee. Your machine must manage to achieving these results.