EarthTalk: Efficient air conditioning
Updated 11:09 am, Thursday, May 16, 2013
Dear EarthTalk: Now that hot weather is coming, I want to upgrade my home's A/C. Which are the most energy-saving models and should I go central air or window units? -- Jackie Smith, Cary, N.C.
According to the American Council for an Energy Efficient Economy (ACEEE), energy consumption for home air conditioning units accounts for more than 8 percent of all the electricity produced in the U.S., at a cost to homeowners of $15 billion annually. Besides the cost, all this cooling leads to annual emissions of about 195 million tons of CO2 -- or 2 tons per year for each American home with A/C.
Of course, foregoing A/C entirely is the most energy- and cost-efficient way to go, but some of us need a little cooling for comfort, especially in warmer climates. If A/C is a must, buying the most efficient model is the way to save money and pollute less. Fortunately, a new generation of much more efficient room and central A/C units means that upgrading will likely pay for itself in energy savings within just a few years.
The main factors to consider in choosing a new model are cooling capacity (measured in British Thermal Units, or BTUs) and Energy-Efficiency Ratio, or EER. To determine the correct BTU rating for a given space, multiply the square footage by 10 and then add 4,000. Meanwhile, a given unit's EER is the ratio of cooling output divided by power consumption -- the higher the EER, the more efficient the air conditioner.
According to the U.S. Department of Energy, national appliance standards require room air conditioners to have an EER of 8 to 9.8 or more, depending on type and capacity. Units with an EER rating of 10 or above typically qualify for the federal government's ENERGY STAR label, which appears on especially energy-efficient appliances. Check out the ENERGY STAR website for lists of qualifying A/C models.
The Association of Home Appliance Manufacturers said the average EER of room A/C units rose 47 percent from 1972 to 1991. To wit, replacing an older room unit with an EER of 5 with a new model with an EER of 10 would result in a 50 percent energy cost savings associated with A/C.
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As to whether room units or central A/C makes more sense, it depends. Room units, which only cost a few hundred dollars each, will suffice for renters or those who only need to keep one or two rooms cool at a time. Meanwhile, central A/C is more efficient overall at keeping a whole house cool, and will also do a better job at reducing household humidity than even several individual room units -- and will save more money faster on electricity bills. But with a starting price of around $4,000 for the condenser and initial set-up (plus any duct work needed to distribute cool air around a home), central A/C isn't for everyone.
ACEEE points out that there are ways to keep indoor space cooler without A/C: improving insulation, sealing air gaps, getting rid of old appliances and light bulbs that give off lots of heat, running fans, using cooler colors on exterior roofing and paint, and other strategies. Those in particularly arid climates might also consider installing a swamp cooler (which cools outside air by running it over cold water) as a cheaper alternative to A/C. By following these suggestions and upgrading conscientiously, we can all stay a little more comfortable in our warming world without exacerbating the problem too much.
Dear EarthTalk: What are the big delivery companies like FedEx and UPS doing to green their truck fleets and operations in general? -- Mitchell Glaser, Overland Park, Kan.
Package delivery companies like FedEx and UPS have come a long way in a relatively short time regarding sustainability, but they still have considerable room for improvement. While there is only so much these companies can do to reduce their huge carbon footprints -- given their reliance on emissions-heavy air transport -- they've made great strides in greening their ground fleets, optimizing their choices of modes and otherwise streamlining energy use.
For its part, UPS was an early adopter of cleaner vehicles, and today operates upwards of 2,500 low-emission vehicles that run on alternative fuels and technologies. The company is particularly jazzed about a new generation of hydraulic hybrid package delivery trucks unveiled in the fall of 2012 in partnership with the U.S. Department of Energy's Clean Cities program. These new trucks -- which employ a diesel combustion engine along with a hydraulic high-pressure accumulator that stores energy captured during braking -- get 35 percent better fuel economy and generate as much as 30 percent fewer greenhouse gas emissions as compared to the non-hybrid diesel-powered vehicles they are replacing. While these trucks may cost UPS $7,000 apiece more than their traditional counterparts, the company estimates the upgrade will save $50,000 or more, while substantially reducing emissions, over the lifetime of each vehicle.
UPS has also been blazing new trails in operational efficiency via intermodal shifting, e.g., using the most fuel-efficient transport mode (airplane, train, truck or ship) or combination of modes to meet customer needs. A concerted effort by the company to streamline its operations in 2011 led to savings of two million metric tons of greenhouse gas emissions by moving delivery volume from air (the most emissions-intensive mode by far) to ground, and another 800,000 metric tons by shifting volume from ground to rail.
Meanwhile, FedEx, with one of the largest hybrid-electric fleets in the industry and upwards of 2,000 alternative energy vehicles in service worldwide, is no slouch either when it comes to green streamlining. Back in 2008 the company worked with the Environmental Defense Fund (EDF) in setting the ambitious goal of improving the fuel efficiency of its worldwide fleet of Express delivery vans and trucks by 20 percent within a dozen years. Then early in 2013 the company announced that it had already exceeded its goal seven years ahead of schedule (with an overall savings of 22 percent so far) but was also upping its goal to a 30 percent fleet-wide efficiency gain by 2020.
With a strong commitment to swapping out older vehicles with newer more efficient ones, the company is well on its way. It now operates 360 hybrid-electric trucks and 200 electric vehicles and is replacing many of its delivery trucks with "right-sized" Sprinter-type vans that are as much as 100 percent more fuel efficient than their predecessors. FedEx has also been upgrading its fleet of Express diesel trucks to cleaner-burning models, and is making similar upgrades in its Freight and Ground divisions as well. Likewise, the company is well on its way toward reducing greenhouse gas emissions from its airplanes by 30 percent by 2020.
EarthTalk is by Roddy Scheer and Doug Moss of E -- The Environmental Magazine (www.emagazine.com). Send questions to email@example.com.