A combi (combination) oven does three jobs in one cavity: dry convection heat, steam, and a combination of both. That lets one box roast, bake, steam, poach, proof, and reheat — which is why buyers compare "combi oven vs convection oven." A convection oven only does dry heat; a combi adds precise humidity control, so meats stay juicier and you can run steam-heavy and dry cooking on the same unit. The cost of that flexibility is a higher price and real installation requirements.
Just like steamers, the core split is how the oven makes steam. A boiler (steam generator) combi keeps steam ready for fast, powerful, consistent output — ideal for heavy steam use and volume — but the boiler needs treated water and periodic descaling. A boilerless combi injects water onto a hot surface or element to flash it to steam; it uses less water, costs less to maintain, and takes up less complexity, but very heavy continuous steaming can out-pace it.
| Feature | Boiler | Boilerless |
|---|---|---|
| Steam power / recovery | Higher, consistent | Good for most loads |
| Water use | Higher | Lower |
| Maintenance | Descale boiler regularly | Simpler, less scaling |
| Best for | Heavy, continuous steam volume | Most kitchens, lower running cost |
Combis are sized by pan count — how many full-size (or half-size) pans fit on the racks. Match capacity to peak covers and available floor and door space.
Buy a size up only if your rush truly needs it — an oversized combi wastes energy and floor space.
Tip: The combi itself is the easy part — the utilities trip people up. Confirm water treatment, drain type, and power or gas before you sign the purchase order. Retrofitting a drain or a three-phase circuit after delivery can cost more than the difference between models.
Water: combis need a supply, and boiler models demand treated water — manufacturers commonly specify hardness limits around 5–7 grains per gallon (well under 70 ppm). A filter or softener sized for steam production is usually mandatory; hard water is the number-one killer of combi boilers. Drain: plan a floor drain (often 1" minimum, heat-resistant material like CPVC or copper — not plain PVC, which can warp during hot rinse cycles) within a few feet of the oven and not directly under the legs. Power: electric combis range from 208–240V single-phase on a 6-pan to 208–480V three-phase on 10-pan and larger. Gas: a 10-pan gas combi can demand roughly 70,000–120,000 BTU/h; size the gas line for it and plan a flue.
Combis produce steam and some grease vapor; many jurisdictions require a condensate or Type I/Type II hood depending on what you cook. Check with our do I need a hood? tool, size exhaust with the hood CFM calculator, and confirm local requirements. Electric combis are simpler to install and heat evenly; gas can cut running cost where electricity is expensive — see our gas vs electric guide. If you mainly need steaming, compare against a dedicated unit in our commercial steamer guide.