Energy saving air conditioners
If you're like most North Americans, an energy saving air conditioner can make a big dent in your household energy budget. And with energy prices on the rise, you'll definitely want to do what you can to make better use of your current air conditioner, or find the most efficient new one you can afford.
The good news is that there's lots you can do to cut cooling costs whether you're sticking with your current air conditioner or planning to buy a new high efficiency air conditioner. Most air conditioning systems sold today are energy saving air conditioners, compared to the models sold ten or twenty years ago (at least in the US and Canada).
In this article I cover general guidelines for energy saving air conditioners, such as how and when to buy, maintaining proper refrigerant levels, and how to get the most out of your energy saving air conditioner using as little energy as possible.
I also cover other air conditioner-related topics in separate articles linked below:
- How air conditioning works
- Efficient central or residential air conditioning units
- Efficient window AC units
- Home air conditioning problems
- Air conditioning ratings
- Solar powered air conditioning
- Trane AC unit - one of the more efficient central air systems on the market
- Nordyne air conditioner - probably even better than Trane - with ultraefficient SEER 21 to 24.5 central air units and ultra-quiet iQ Drive technology
Cutting your energy use from air conditioning can make a big difference to your total energy budget. In the US alone, home air conditioning use accounts for $11 billion in energy costs each year, and results in the production of roughly 100 million tons of CO2. If every American household that currently has an air conditioning system (about 65% of all households) were to upgrade to the most energy saving air conditioner available for their home configuration, Americans could eliminate perhaps 40 million tons of CO2 emissions per year.
General guidelines for air conditioner efficiency
Is your current air conditioning system efficient or is it time to upgrade to a new energy saving air conditioner? What does cleaning your energy saving air conditioner do to energy efficiency? Are there ways to make your existing unit an energy saving air conditioner even if it's not the newest, most energy saving air conditioner available? What is refrigerant charge and what impact does it have on efficiency? What should you look for if you do decide to buy an energy saving air conditioner? All these questions and more are covered in this section.
Is it time to buy a new high efficiency air conditioner?
If your unit is more than ten years old, or cycles rapidly when in use (on / off / on off), it is probably time to buy a new energy saving air conditioner, as efficiency standards for air conditioning systems keep increasing, and you will probably save more than 20% on your electricity bill by upgrading to an energy saving air conditioner. If your central air conditioning system is more than ten years old, it may have been oversized at the time of installation, as installing oversized units was once common practice. An oversized unit, it turns out, is much less efficient than one slightly undersized for the area being cooled, so even if modern air conditioning systems weren't more efficient on average than 10-year-old units of the same BTU output, you could wind up saving money by upgrading. To see if your unit is oversized, ask an HVAC contractor to check its BTU rating for you and to do a sizing on your house to determine whether it was oversized.
See the sections on buying a new high efficiency air conditioner on my Efficient central air conditioning and Efficient window AC units pages.
Refrigerant levels are critical to optimum AC efficiency
Good quality energy saving air conditioners for window or through-the-wall installation are shipped with the correct amount of refrigerant (known as the refrigerant charge) for efficient operation. Central air conditioning systems have their manufacturer-recommended refrigerant charge added by the licensed HVAC company doing the installation - but a poorly trained installer may install too much or too little refrigerant. For both types of air conditioning system, the refrigerant charge may decrease over time due to leaks. If the performance of your air conditioning system seems to diminish over time, or it's working harder this summer than it was last summer to do the same amount of cooling, the refrigerant charge may be a problem.
For a central energy saving air conditioner, you should have the unit serviced to preserve its efficient operation. The service every couple of years (more often if you use it much of the year) should include a test of the refrigerant charge, and the charge level should be noted on the invoice. Also ask the technician to verify that the refrigerant charge is correct for the unit, not just sufficient. There should not be too much refrigerant. Keep your maintenance invoices so you can ensure the refrigerant charge stays the same. If it drops from one servicing to the next there may be a leak, which needs to be fixed by a technician before more refrigerant is added.
Keep the unit clean
For either central or room units, keep your energy saving air conditioner clean. Any exposed coils, vents, fins, filters, or other parts where heat is vented, air passes through, or where moving parts are exposed to the air should be kept free of dust and moisture. Make sure any condensate from a window unit is properly drained to the out of doors, preferably away from the house so that it does not drip on your foundation and increase basement humidity problems. For a central unit, make sure the unit is cleaned by having annual maintenance performed.
Never turn the temperature way down to speed cooling
Turning your energy saving air conditioner down to a very cold setting won't make any difference to how fast the room cools, and suddenly you'll be (A) freezing and (B) wasting energy if you forget to turn the unit back to a reasonable temperature setting. The temperature control on your energy saving air conditioner only determines at what low temperature the unit will stop cooling, not how much cooling effort it will expend at any given time.
Anticipate hot days and cool early
It uses less energy for the air conditioning system to cool a room down to the desired temperature, when it's still cool outside. Don't wait until it's scorching hot outside. Better yet, if it's cool at night, open the windows first and draw in as much cool outside air as possible before turning on the air conditioning system
Anticipate departures and turn units off early
It's not terribly efficient to run your energy saving air conditioner while you're out of the room or house being cooled for more than a half hour. It takes much less time for an AC unit to start making a room or house comfortable, than for it to keep the space comfortable for non-existent occupants. So if you're planning to head out, turn the room unit off ten minutes before you leave, or the house unit off half an hour before you leave.
Don't believe anyone who tells you it's more efficient to let the unit run all the time, rather than to let the temperature in your house rise when you're not around. No house is perfectly insulated; some heat always creeps in from outside when it's cooler out than in. The greater temperature difference between outside and inside, and the more poorly insulated or sealed the house, the more energy will pass through the walls as the two temperatures strive to meet equilibrium. Since leaving a unit on all the time means you are maintaining a greater temperature difference, you are causing greater energy exchange with the outside, which means greater energy consumption by the air conditioning system.
And don't forget that sometimes the errand you think is going to take ten minutes can expand to two hours (you remember another thing you need to pick up, you meet a friend and chat, you have a fender bender). If you leave your energy saving air conditioner running on the assumption you're just stepping out for ten minutes, but you're gone much longer, you've just wasted a good deal of electricity.
If you don't want to come back to a warm, clammy room or house, you can put a room air conditioner on a timer (or use its built-in timer if it has one), and set it to turn on a few minutes to half an hour before you return. But remember that a separate automatic timer must be able to handle the amperage of your unit; some automatic timers are only designed to turn lights on to make your house appear occupied.
For a central air conditioning system, if you are leaving during one step of the daily cycle but returning at another part, it is safe to raise the temperature when you leave, as programmable thermostats will revert to the regularly programmed temperature setting when the next phase of the program kicks in. For example, suppose you have your thermostat set to: 6:30 a.m. 78F, 8:30 a.m. 83F, 4:30 p.m. 78F, 10:00 p.m. 83F. If you are leaving the house early, say at 7:00 a.m., you can turn the temperature up to 83F without reprogramming the unit; the house will still start to cool down to 78F at 4:30 p.m., but you'll save the cost of keeping it cool from 7:00 a.m. to 8:30 a.m.
Use an energy-saving temperature setting
Your rooms should be cooled to between 23-26C (73-79F). Use the highest temperature in this range you can comfortably live in. You'll save a lot more if you set your cooling temperature to 26C/79F than if you use the lower end of the range.
Supplement your air conditioning system with fans
Use ceiling fans and room fans to blow your air-conditioned indoor air around, in rooms where people are present. This will help them keep cool, and you'll be able to raise the air conditioning system thermostat setting by 2-4F (1-2C) without anyone noticing a decrease in comfort over a room that's air conditioned without a fan. Compared to air conditioning systems, fans use practically no energy at all.
Follow these summer energy saving tips
Over and above these tips specific to making your air conditioning system more efficient, follow my summer energy saving tips, which cover a wide range of things you can do to save energy in the summer, including tips to keep your house cool without using air conditioning as much (or at all).
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