If you are trying to roast a chicken or cook a pan of lasagna, you won't have much luck doing it without any heat. The reasons why your oven won't heat can vary, but you can usually narrow it down quickly with a little know-how and some investigation. Look to the most common reasons first, and you are likely to find your answers.
The electrical heating elements inside your oven require electricity to work. If there is no electrical current to the oven, it will not heat up. Check to make sure the switch in the circuit breaker box assigned to the oven is in the "on" position and has not tripped because of an overload. If it has, turn it back on. If the breaker switch flops back and forth and does not lock into either position, it may need to be replaced. Be sure the oven is actually plugged into the outlet and that the outlet is the correct type and is functioning correctly.
The heating elements inside the oven are the components that make the oven get hot. Eventually these elements can burn out. If they malfunction, they won't heat and and turn red as they typically do when they get hot. These elements can be replaced easily and often plug in without the need for tools or experience. If you are not comfortable replacing elements, have an appliance technician do it for you. Remember that the oven should always be unplugged and turned off when repairs are made.
Knobs and Switches
Ovens have several knobs and switches, depending on the make and model. These controls are there so the user can set the appropriate temperature and turn the oven on and off as needed. If you do not turn on the knobs and switches that power up the elements, they will not heat. Consult your manual to make sure you have everything set correctly for cooking.
The thermostat has a switch in it that turns the heat source on and off to maintain a certain temperature, according to temperature you have set. If the thermostat is malfunctioning, it might not be able to turn the heat on. With the power turned off at the breaker or the unit unplugged, an electric meter will test the continuity of the thermostat. This is a simple test for most appliance repair technicians.