The answer to 'why is my water heater high energy bills' is that your water heater may be inefficient, have issues, or be the wrong size for your home. Common causes include sediment buildup, thermostat problems, a leaky tank, or the heater being too large or small for your hot water needs.
If your water heater is more than 10 years old or you notice the tank leaking, the pilot light going out frequently, or your hot water running out quickly, it's likely time to replace the unit. Upgrading to an energy-efficient model can significantly reduce your energy costs. However, if the issue is a minor problem like a thermostat malfunction or sediment buildup, you may be able to make some DIY repairs. But for any major issues, it's best to call in a professional HVAC technician to diagnose and fix the problem correctly.