Some ideas are so widely held that they appear to bear little scrutiny or even a second thought. While often factual, such common wisdom is often based on outdated or false information. Widespread misconceptions about home energy use can increase a homeowner’s energy bills, and lead to unnecessary home maintenance and reduced comfort. Here are 10 common home energy myths that may be costing you:


    1. Setting the thermostat higher or lower will heat or cool your home faster. Adjusting the thermostat higher or lower than necessary will not heat or cool your home faster. Furnaces and air conditioners work at the same speed, no matter what the thermostat setting. A home will warm up to 70ºF just as quickly if the thermostat is set at 70ºF as it will if it is set at 80ºF. In fact, more energy may be wasted as the heating or cooling system continues to run to reach the higher set point.
    2. A heating and cooling system works harder to reach a comfortable temperature after setback or set forward. Many homeowners fail to adjust their thermostat at night or when they are away because they believe the heating or cooling system must work harder or use more energy to reheat or re-cool the house; that is not how a thermostat works. The system turns on to reach a set level and shuts off when that level is reached. It operates more like a switch that turns on and shuts off than a car that accelerates when you step on the gas pedal.
    3. Energy efficiency and energy conservation are the same thing. Efficiency refers to using less energy to perform a specific task. For example, compact fluorescent lamps (CFLs) can light your home more efficiently than conventional incandescent bulbs. Conservation involves reducing your need for energy through behavioral changes, such as setting your thermostat lower.
    4. When an appliance is turned off, it is off. Many appliances and electronic devices continue to use small amounts of power after they have been turned off—sometimes as much as when they are on. This is known as standby power or phantom load. The only way to stop the drain of power from these devices is to unplug them or use a smart power strip that will completely cut their power when not in use.
    5. Leaving lights and electronic devices on uses less energy than turning them on and off. In most cases, the small surge of power needed to start a device is much less than the power wasted by leaving it on when it is not needed.
    6. Duct tape is the best choice for sealing ducts. Duct tape has very low durability when used to seal ducts. The adhesive dries out over time and the tape starts to wrinkle. Mastic or metal-backed tapes—available at your local hardware or do-it-yourself retailer—are better choices for duct sealing.


  1. CFLs are more harmful for the environment than traditional bulbs because they contain mercury. CFLs do contain a trace amount of mercury that can be emitted into the atmosphere if the bulb is broken. However, mercury is also emitted into the atmosphere through electricity generation. Using CFLs will help to reduce mercury emissions because they are more efficient and use less electricity. A 60-watt incandescent bulb will produce 5.8 milligrams of mercury emissions over its lifetime from energy generation, according to the U.S. Environmental Protection Agency, while a comparable CFL bulb will yield only 1.8 milligrams.
  2. Purchasing an efficient air conditioner or furnace will automatically reduce energy bills. This is true to an extent, but proper sizing and installation is necessary to optimize savings. Installing an efficient, but oversized system may negate much of the potential savings, while a poorly designed duct system will also reduce efficiency and comfort. Windows, doors and insulation also affect heating and cooling efficiency.
  3. Dimming Incandescent lights by 50 percent will cut lighting costs in half. In reality, the relationship is not quite direct and the savings may be less than expected. Dimmed incandescent lights do use less power, but when lights are dimmed, the voltage drops and the filament becomes cooler. This causes a loss in overall efficiency.
  4. Closing off vents will help to lower heating and cooling costs. Typically, closing or covering up vents is not a good way to save on energy costs. Heating and cooling systems are balanced through the duct system; closing vents throws the system off balance. Pressure can build up in the ductwork, causing leakage and reducing the amount of air circulating in your home. This reduces system efficiency and comfort.

Knowing the facts about energy use can help you save money and stay comfortable. Search the Energy Library for information about how to make your home more energy efficient.

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For more information about NHSaves efficiency programs and possible incentives see our Save at Home section.

This article has been prepared solely for the purpose of providing helpful information to users of this service. The information has been compiled by Questline, a contractor to the NHSaves utilities; however, no representation is made by either Questline or NHSaves as to the completeness or accuracy of the information contained therein. In particular, some information may be incomplete, may contain errors or may be out of date. In addition, neither Questline nor NHSaves endorses any product or service mentioned therein.

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