Keeping the foodservice equipment marketplace up to date with the latest menu and concept trends.


Specifying Energy-Efficient Ovens

In the grand scheme of commercial kitchen energy use, convection ovens don't pose a huge drain on costs compared to refrigeration or even fryers. But that doesn't mean their impact on total kitchen energy use is negligible. In fact, the Food Service Technology Center is diligently working to revise standards for ovens, including rack, conveyor and combination units.

The FSTC also encourages manufacturers to consider revamping current convection models with better controls and insulation. This comes on the heels of a growing demand among chain restaurants for full-kitchen energy savings.

In a trickle-down effect, these monster chains with big budgets and high standards for efficiency continue to motivate smaller operators to seek out more energy-efficient equipment, and that includes ovens, says Cris Gross, Upper Michigan regional manager for Stafford-Smith, a Kalamazoo, Mich. dealer, and FE&S' 2009 DSR of the Year. "I've seen a lot more interest in total kitchen energy efficiency over the past couple of years. Relatively speaking, though, ovens are already slightly energy efficient."

Gross notes that on average, ovens use 44,000 BTUs per hour versus energy-sucking fryers at 90,000 BTUs (energy efficiency when it comes to convection ovens is measured by the number of BTUs used to produce a particular food in a particular amount of time). However, with utility costs on the rise, more operators need to save wherever they can.

Currently, Energy Star works with convection ovens but not with conveyor, rack, deck, counter or combi ovens, says David Zabrowski, senior engineer for the Food Service Technology Center in San Ramon, Calif. And it would seem that it will be a year or more before Energy Star develops a standard that encompasses other types of ovens. That is largely due to the EPA's new requirements for third-party Energy Star certification and verification testing standards that have increased workloads for standards organizations and companies like FSTC. Making matters even more complicated, the Department of Energy has threatened to impose fines on manufacturers that don't meet their separate third-party testing standards, so that political dynamic has thrown the proverbial wrench into some existing plans to add product categories to Energy Star.

Setting the Standards
Meanwhile, the FSTC has managed to continue working diligently to get combi and other ovens on board with Energy Star requirements because of the increasing consumer demand.

In the past, the standards for convection ovens were based on a five-pan oven but many ovens can range anywhere from three-pan capacity to six- or more pan capacity. As a result, a lot of manufacturers of three- and six-pan ovens, for example, that may have Energy Star potential have been kept out of the game because of the current standards.

The other issue is that the current standards only measure full-size and half-size gas and electric convection ovens but those sizes can still vary. For example, one manufacturer has a four-rack oven with an optional additional fifth rack that can be added on, but doing so changes the overall size of the oven. Examples like those have thrown off consistency in testing results.

"We're in the process of looking at that now and trying to come up with an energy-per-pan rating that would expand the category to other size ovens," Zabrowski says.

Combi ovens bring even more confusion into the mix, but the FSTC has been working on revising those standards, too. In the past, steam and convection cooking were measured together, and chicken was the common denominator. Or not: the FSTC found that chicken products vary wildly, as do the way combis cook and the amount of steam and dry air they utilize when cooking chicken.

"After two and a half years working with the industry we finally ended up with a method where we evaluate the combi while its in convection mode and then do that with the steaming mode and report both sets of numbers," Zabrowski says. Treating them like separate entities has required the use of two different products, too. "We've moved away from protein products, so now we use a russet potato for measuring the convection mode in combis, which is the same russet potato used for traditional convection ovens. And we use the same red potato for the steam mode that's used to evaluate steamers." The consistency in results and reporting have improved tremendously, Zabrowski says.

As a result of the new testing standards, the old data is no longer valid, so the FSTC has been hard at work building up the new data set. "With rack ovens, we had a good standard, but not enough data. With combi ovens, we had plenty of data, but a low standard," Zabrowski says.

Convection or Combi
Comparatively, combi ovens are naturally more efficient than convection ovens because they have to have better insulation due to their steaming capabilities, Zabrowski says. "Combis use rubber gaskets to seal their doors and generally have better seals because they steam, so they have to," Zabrowski says. "Convection ovens use metal, so after you've operated the oven a few times, the metal will already begin to fatigue."

Run your hand over the front of a combi and a convection and you'll instantly understand Zabrowski's point. Convection ovens have noticeably more heat coming through to the outside than their dual-functioning siblings, he says.

Combination ovens also have higher end controls, and that is partially the cause for their higher price point in general. But these controls also have an energy-saving component in that they efficiently cook what's needed in the amount of time needed, and then they shut off, retaining their heat for hours at a time before reuse, again as a result of the better door seals, according to Zabrowski. Convection ovens, on the other hand, tend to take longer to heat back up again so many operators simply keep them running all day, and that means a greater energy drain.

"There is a lot of room for improvement," Zabrowski says, in terms of design and manufacturing. Convection ovens could be retrofitted with better controls and better door insulation, but that comes with a price tag that many manufacturers, and operators for that matter, just don't want to pay.

While combis are much more expensive than convection ovens, those costs can often be more easily justified because they do more than just convect hot air; they also steam, slow-roast, and dually-cook a wider range of products with less overall work and in one set space.

There's also a greater efficiency component when it comes to combis because of their set recipe programming: the ovens cook exactly with the power they need to cook the specific recipe at hand. When they're not instructed to cook anything, they power down. But combis come with far greater staff training than traditional convection ovens because of the complexity in programming and controls.

One also hopes staff doesn't spray down the controls when cleaning at night with a hose, which compromises the unit's ability to function properly. Because, Zabrowski says, that does happen.

Other Buying Considerations
While energy standards continue to improve for convection ovens, in the meantime, there are buying considerations and operational changes that can help save even more energy in the long term.

First, convection ovens come with a range of potential power, so knowing the product the operator is cooking in those ovens is the first consideration, Gross says. "If you're a steakhouse that bakes off a lot of prime rib, that's a dense product and you want an oven with more BTUs that will deliver your cooking results in less time," says Gross. On the other hand, bakeries cook much more delicate products so strong firepower would only cause burning. "You'd much rather hit a rack of bread with 44,000 BTUs than 90,000 in this case," he says.

Next up: durability. If the oven isn't powerful enough for your product, it will just take more time to cook, thereby using more energy. "Even if an oven is energy efficient, if it's not reliable you're still wasting money," Gross says.

Idling By
After selecting the right oven, managing idle time is the next step toward greater energy savings. "An operator may look to replace an existing oven with an energy-efficient one, but the oven is still generating power if it's on but not cooking," Gross says. "Idle time is very important."

In fact, when it comes to combi ovens, operators can shave between $400 to $800 annually off electronic models by cutting out two hours of idle time per day, according to the EPA. Other energy-saving tips include scheduling on and off times for the equipment based on peak and non-peak production periods, posting those schedules so staff can see them, and training the first-shift staff not to start up the convection ovens the minute they walk in the door. Of course, that's always easier said than done.

That's why some manufacturers have looked to improve heat recovery on their ovens as a way to encourage regular powering up and powering down, rather than just powering up and staying that way. In fact, some newer conveyor oven models on the market now come with idle time management similar to variable-speed technology for hood systems, according to Zabrowski. "When you put the product on the belt, the oven goes to high to get the product through, but then it powers down to low again," he says. Some conveyor ovens that work this way can still run hundreds of pizzas through during a shift, just like their less energy-efficient competitors.

When it comes to energy efficiency and all convection-type ovens, there's still room for advancement, Zabrowski says. "I would really like to see convection oven manufacturers step up and make ovens that are more efficient," Zabrowski says. "Energy Star was a good step in the right direction, but when I look at the potential of that product category I think there is a lot of room for improvement. The question is, how much does it cost to get to that level of equipment?"