Why Your Oven Takes Too Long to Preheat
Quick answer: a slower-than-usual preheat time points to one of three places depending on whether your oven is gas or electric — a weakening igniter, a bake element that’s lost some of its output, or a temperature sensor giving an inaccurate reading — and knowing your oven’s fuel type narrows it down immediately.
“Oven used to preheat in about ten minutes and had crept up to almost thirty. Vlad checked the igniter glow on our gas oven right away and could tell just from looking at it that it was weaker than it should be. Swapped it and we’re back to normal.”
Gas Ovens: Check the Igniter First
The igniter has to draw enough current to get hot enough to ignite the gas — and as it wears, it draws current more slowly, taking longer each time to reach ignition temperature. From a safe distance, watch the igniter glow when you start a bake cycle: a weak, dim, or notably slow glow compared to a strong, steady orange is a clear sign it’s on its way out, even before it fails completely.
Electric Ovens: Check the Bake Element
A bake element that’s partially failed can still glow and produce some heat, just not at full output — which shows up exactly as a longer preheat time rather than an outright failure. Look along the full length of the element for any visible blistering, bulging, or a break, which confirms the diagnosis without needing any tools.
Both Types: The Temperature Sensor Can Be the Real Culprit
If the sensor inside the oven cavity is giving an inaccurate reading, the control board may believe the oven has already reached temperature well before it actually has — or conversely, keep calling for more heat past the point it’s genuinely needed, which reads to you as a slow preheat even though the heating source itself is working fine. This is worth testing if the igniter or element both look visually normal.
Check the Door Seal
A door that isn’t sealing fully lets heat escape continuously during preheat, forcing the oven to work longer to reach and hold its target temperature. Run your hand around the door seam while the oven is heating — a spot where you can feel heat escaping points to a gasket that needs replacing.
Don’t Overlook Something Simple: A Miscalibrated Thermostat
Some ovens drift out of calibration over years of use without any part actually failing — the oven may be reaching temperature faster than the display suggests, or genuinely taking longer than the setting implies. An inexpensive oven thermometer placed inside during preheat tells you quickly whether this is a calibration issue rather than a component fault.
How Much Slower Is ‘Too Slow’?
Most ovens should preheat to 350°F within roughly ten to fifteen minutes. If yours is regularly taking twenty-five minutes or more for the same target, that’s a meaningful enough change to investigate rather than something to simply get used to.
What You Can Check Yourself
Watching the igniter glow, visually inspecting an electric element, checking the door seal, and testing with an oven thermometer are all safe things anyone can do without opening the oven up. Replacing an igniter or element, or testing the sensor’s actual resistance, is where most people bring in a technician — both parts are usually straightforward once accessed, but access varies significantly by model.
Why This Is Worth Fixing Rather Than Working Around
A slow preheat isn’t just an inconvenience — it usually means the same component will eventually cause uneven cooking or, in the case of a failing igniter, an oven that occasionally fails to ignite at all. Addressing it while it’s still “just slow” is easier and less expensive than waiting for it to become “doesn’t work.”
Preventing This From Recurring
There’s not much routine maintenance that prevents igniter or element wear — both are wear items with a finite lifespan. Keeping the door seal clean and checking it periodically for a firm seal is the one preventive step that genuinely helps, since a failing seal accelerates wear on the heating components by forcing them to work harder for longer on every single use.
One More Thing Worth Checking: The Vent System on Convection Ovens
If your oven has a convection fan, a fan that’s stopped circulating air can also make preheat feel slower, since it’s no longer distributing heat as efficiently around the cavity even if the actual heat source is working fine. Listen for the fan running during preheat — silence there is worth mentioning to a technician alongside the slow preheat itself.
Frequently Asked Questions
Is a slow-preheating oven dangerous?
Not immediately, but a weak gas igniter can eventually fail to ignite reliably, which is worth addressing before it becomes an inconsistent no-heat situation.
How do I know if my oven is gas or electric?
Check your owner’s manual or look for a visible heating element (electric) versus a igniter and gas burner tube (gas) inside the oven cavity.
Can I test the oven’s actual temperature myself?
Yes — an inexpensive oven thermometer placed on a middle rack during preheat gives you a real reading to compare against the display setting.
Is an igniter expensive to replace?
It’s one of the more affordable oven repairs — the part itself is inexpensive, with labour depending on how accessible it is on your model.
Could this be a control board issue instead?
Possible, but far less common than the sensor, igniter, or element — worth ruling those out first since they’re more likely and cheaper to fix.
Should I keep using the oven while it’s slow to preheat?
It’s generally safe to keep using it, but plan extra time and have it checked soon — the underlying cause tends to get worse rather than resolve on its own.
*Same-day service is offered whenever possible and depends on technician availability, parts, and your location within the GTA.