Many people who are looking to either replace an existing wall oven, or are shopping for a remodel or new construction have no idea the recent advances in ovens. Over the past 10 years, the appliance industry has made many exciting advances that make cooking more predictable and enjoyable. This is certainly an area where the "proof is in the pudding"!
Convection or Thermal Ovens?
I don't assume anyone I talk to know what convection is, or the benefits. The vast majority of people have never cooked with convection - why should they know? Here is an explanation of thermal and convection ovens...
Thermal Ovens: This is the standard bake and broil oven most people are used to. Although there are differences from brand to brand, most manufacturers provide ovens that produce pretty even results. Most modern ovens will be heated evenly when the oven is preheated properly. If you've never had convection before, are on a tight budget, or if you're a Swanson's T.V. dinner person, you may never miss it.
Convection Oven: Convection has to do with air (in this case, hot air) being circulated in the oven. The movement of the air will cook the food faster and in most cases more evenly. Gas ovens naturally convect, and the byproduct of the fuel combustion is moisture. Some gas ovens will also include a convection fan, too. Electric ovens produce a dry heat and tend to dehydrate food. Introducing convection (via a fan and usually with an additional heating element around the fan and hidden behind a baffle in the back of the oven) can help to sear the outside of what you are cooking - meats being the best beneficiary. When you sear, moisture is sealed inside. Because of this, it is a great idea to get meats off of the floor of a pan with a wire rack so the heat can engulf the prime rib, turkey, etc. Baked goods benefit, too, because of a typically even heat most convection ovens produce. You may be able to cook up to 6 racks of cookies at once with even results.
Because convection cooks faster, you need to compensate for it by either adjusting the time or temperature. A pretty good rule of thumb is the 25 / 25 rule. For meats, use the same temperature you've used over the years in the bake oven, but shorten the time 25%. So for a cooking time of 1 hour, it now becomes 45 minutes. For baking, lower the temperature 25 degrees (Fahrenheit). This is not a perfect rule, but gets you very close to the pin. Most convection ovens today - especially premium brands - offer temperature probes to take the guess work out of it. Set the cooking temperature, then the internal temperature and the oven will let you know when the food is ready!
There are several convection modes available. Be careful when comparing brand to brand / feature to feature. Not all brands will call their convection modes by the same name. Dacor will call their bread and butter convection mode "Pure Convection", while Miele will call theirs "Convection Bake". This can be very confusing as most ovens will have a convection bake mode that cooks very differently. 5 minutes spent with your salesperson or owner's manual about the cooking modes is time very well spent. Ask if there is a demonstration available where they cook for you and explain the different modes. Learn how to use convection if you purchase and oven that offers it! It is a waste of money to not use the mode that produces the magic convection gives you.
Regardless of the oven you purchase, here is an important tip, (as my former Dacor rep used to say) "There ain't no cheatin' in pre-heatin'!" All ovens will let you know when they have reached your desired temperature. Most will get there in under 15 minutes for 350 degrees. But the moment you open the door, all that ambient heat leaves the oven. You now have an oven that is about 230 degrees inside. This is why your cookies come out uneven. For the best results, it is recommended you pre-heat your oven for a minimum of 30 minutes.