If I shut off my heater/air conditioner when I'm gone from the house, does it cost more to heat/cool the house back to the right temperature once I return?
The rate of heat transfer from your house to the outside, and vice versa, is dependent partly on the temperature difference between your house and outside. More heat is transferred when the difference is greater, so it takes more energy to keep your house at 72°F when it is 40°F outside than to heat your house back up to 72°F after you return.
With air conditioning systems, the equipment runs at peak efficiency when it operates for long periods. Cooling your house back to the comfortable temperature will use less electricity than the unit would use cycling on and off for short periods to maintain the set temperature. If your house takes too long to get back to a comfortable temperature, you might investigate getting a programmable thermostat, and set it to start heating or cooling your house an hour or so before you return. You could also set the thermostat back, to a lower temperature for heating, or a higher one for cooling, while you are gone, rather than turning it off completely.
Will installing a programmable thermostat reduce my heating and cooling consumption?
Programmable thermostats can reduce the energy used for air conditioning or heating by 5 to 30%. Just installing the thermostat isn't enough; you need to enter a schedule designed to be sure the heating and cooling systems do not run when not needed, and are set back when the comfort needs are more flexible.
Programmable thermostats, while not always digital, save money by turning the air conditioner to a higher setting (or heater to a lower setting) when no one is in the house, or in the evenings when it is cooler. You can achieve the same savings without the programmable thermostat, but you would have to remember to change your thermostat every day when you leave the house, and turn it down every night when you go to bed. In addition, if you are using the thermostat to regulate your heater, you would wake to a cold house. The programmable thermostat does all of the remembering for you once it is set.
My central air conditioning blows cool but not cold air and seems to be always running. I have heard that dirty coils in the condenser could cause this. Is this something I can check and clean myself and, If so how would I go about it?
Problems
1. Your condenser may be dirty.
2. There may be inadequate air flow around the condenser.
3. There might be a leak, or your unit is out of refrigerant.
4. Your duct system might be leaking.
Solutions
1. Have unit serviced annually by qualified heat/cool contractor.
2. Check your condenser. Go outside to the condensing unit, make sure that plants are trimmed at least two feet away from the top and sides of the unit. Make sure there are no leaves, dryer lint, lawn trimmings etc., stuck on or around the unit. Turn off the electricity to the air conditioner. Take a garden hose with a high-pressure nozzle and spray the condenser coils from the inside, forcing debris to the outside. Repeat the process from the outside, forcing any remaining debris inside. Try to knock out any dust, dirt, leaves, etc., that may have accumulated between the heat exchange fins. If any of the fins have been bent so that airflow is impeded, carefully take a thin blunt object like a wooden popsicle stick and straighten the fins. You might want to do this once or twice a year, to keep everything working optimally.
3. Check your ducts. First do a pressure test. While the air conditioner is operating, go to each register and make sure that air is coming out. If there is no airflow from a register, or noticeably less, there is probably a major hole or disconnection along that duct passageway. Second, do a visual check of your ducts if possible. Most houses have leaky ducts, even new houses, so it is likely to find leaks in yours. Typically, leaks occur at bends, joints, and at register connections. A disconnected duct wastes energy by heating or cooling your attic or crawlspace instead of your home. In addition, pollutants and dust can be sucked into your house through a disconnected return duct. If you find a disconnected duct, reconnect it with sheet metal screws and mastic for metal ducts or zip-ties and butyl-backed tape (not duct tape, which degrades rapidly) for flexible ducts. You can also hire contractors to go over your entire duct system, sealing it for leaks.
4. If neither of these things help with the cool air coming from the unit, call an air conditioner contractor. He or she will be able to determine if your air conditioner has the proper refrigerant charge. Sometimes air conditioners are undercharged when first installed and sometimes there is a leak, allowing refrigerant to escape. A pressure test of the coils will determine which is the problem. You might want the contractor to clean the interior coils at the same time. Dust on these coils can reduce airflow, reducing efficiency.
Is there any rating for electric water heaters?
Federal appliance standards require that all water heaters achieve a certain rating on a standardized scale. The rating for water heaters is called the Efficiency Factor (EF), based on the use of 64 gallons per day under standard test conditions.
This Energy Factor can be converted into an estimate of annual consumption for standard operating conditions. This estimate, in kWh/yr is the number you will see on the yellow Energy Guide sticker. For a list of the most efficient water heaters, contact the American Council for an Energy Efficienct Economy (ACEEE).
Here are some general trends in water heater efficiency:
1. Larger tanks tend to be less efficient than smaller tanks, because they have more surface area through which to lose heat.
2. Electric water heaters are more efficient than gas or propane heaters because the latter lose heat from the exhaust gases in the burner. As a result, some of the heat produced just goes up the chimney. However, because electricity tends to cost more than gas, water heating bills are usually higher with electric than gas.
3. Heat pump water heaters are more efficient than electric resistance water heaters because they don't generate the heat used to heat the water; they just move heat from one place to another. Heat pump water heaters cost more to purchase than other types of water heaters.
What is the average setting on an electric hot water heater?
Typically, water heaters have three temperature settings: high, medium and low. These settings correspond roughly, depending on the age and condition of the water heater, to about 160°F for high, 140°F for medium, and 120°F for low. Most people have the temperature set to medium, or around 140°F. If it is not already there, you should consider lowering the thermostat to 120°F, which will save you about 3 to 5% in water heating costs for each 10°F reduction. You might want to consider a timer for your water heater that turns it off when not in use, say between 10 p.m. and 6 a.m. This would also lower your water heating costs by cutting down the amount of energy lost through the walls of the tank during the night.
Do computers and fax machines really use that much energy?
If you use a computer built before 1994, it can use around 200 W, and a laser printer can use around 100 W; if you leave this on 24 hours per day this can add up to over $200 a year. But many computers, monitors and printers built since 1995 have "ENERGY STAR" capabilities, which save a lot of energy when you enable this feature