Yes, a microwave oven will still use a small amount of electricity even when it is turned off but still plugged in. This phenomenon is commonly referred to as "standby power" or "vampire power."
When you turn off a microwave oven using the power button or by opening the door, it goes into standby mode. In this state, the microwave's electronic components, such as the display, clock, and control panel, remain active to be ready for quick use when you turn it on again. Additionally, some microwave ovens have features like a clock or timer that continue to run even when the microwave is not actively cooking.
The amount of electricity consumed during standby mode is relatively minimal compared to when the microwave is actively cooking. However, over time, standby power can add up, contributing to a small increase in your electricity bill. To reduce standby power consumption, you can unplug the microwave when it's not in use or use a power strip to easily disconnect multiple devices at once. Some modern microwaves also come with energy-saving features that automatically enter a more energy-efficient mode after a certain period of inactivity.