Yes, baking 20 potatoes at a time can affect the overall baking time. Here’s why:

1. Oven Temperature Recovery – Adding 20 potatoes at once can cause the oven temperature to drop significantly, meaning it may take longer to return to the set temperature.
2. Air Circulation – If the potatoes are crowded or placed too closely together, hot air won’t circulate as efficiently, leading to uneven cooking and longer bake times.
3. Size & Type of Potato – Larger potatoes or denser varieties may take longer to cook, especially in bulk.

How to Minimize the Impact:

• Preheat Well – Allow extra preheating time before putting the potatoes in.
• Use a Convection Oven – If available, convection baking can help maintain even heat distribution.
• Spacing Matters – Arrange potatoes in a single layer with space between them for proper airflow.
• Check for Doneness – Stick a fork or skewer in the largest potato to ensure it's fully cooked (should slide in easily).

For large russets (8-10 oz each) at 400°F, a single batch might take 45-60 minutes, but with 20 at a time, it could take closer to 60-75 minutes, depending on oven performance.