Humidifiers can impact energy efficiency in HVAC systems. While they add moisture to the air, making it feel warmer and potentially allowing for lower thermostat settings, they do consume additional energy. The energy usage of a humidifier depends on its type and size. Modern, energy-efficient models are designed to minimize power consumption. Properly maintained humidifiers can contribute to a more comfortable indoor environment, but it's essential to consider their energy usage in the context of overall HVAC efficiency.