For most foods, preheating really matter. Preheating an oven is especially important with baking when you use yeast, baking soda and baking powder as leavenings – which react to heat.Food also cooks faster in a preheated oven – you’ve got the right temperature from the get-go and your dish can start cooking immediately and properly. https://eatyourmistakes.com/in-the-kitchen/do-i-really-have-to-preheat-the-oven
So how long does it take an electric oven to preheat to 400 degrees? The typical electric oven will heat up in the first 5 to 20 minutes depending on its strength and target temperature. As experts said, it really depends on the electric oven model and the manufacturer. Generally, we can say that electrical ovens should take around 10 to 15 minutes to preheat to 400 Fahrenheit. https://www.simplyhealthyfamily.org/how-long-to-preheat-an-oven/There are modern ovens that have a fast preheat feature and these ovens can preheat in 7 to 10 minutes to 400 Fahrenheit.