I recently returned from a family vacation to Ireland, where the bed and breakfast I stayed used washers in the cottages but not dryers. Line dry only. My mother-in-law, who still hangs most of her wash out to air dry, would have been impressed.
Turns out that both my Irish hosts and my mom-in-law know way more than I do about the most energy-efficient way to do laundry. A new study conducted by environmental and energy research firm Cadmus Group (called "Do the Savings Come Out in the Wash? A Large Scale Study of In-Situ Residential Laundry Systems") found that while many homeowners obsess about how much energy they can save by laundering their clothes in cold water versus hot water, they should actually be worrying way more about how much energy is going into drying.
Said David Korn, a Cadmus principal:
"Contrary to convention wisdom, the energy use of the washer is not an issue. Hot water used in washing clothes is moderately important, but we found that households only use hot water about 13 percent of the time. The majority of the energy consumed and potential savings arise in reduced operation of the clothes dryer -- not the washer."
Cadmus based its research on data collected by Onset HOBO energy monitoring systems that were connected to washers and dryers in about 115 different households. The locations used different tiers of technologies. Some were Energy Star-rated. Some were not. The capacities of the machines was also different from household to household. A veritable hodge-podge of test systems.
Here are some of the key findings that are detailed in the study:
- Washers that conform to the Consortium for Energy Efficiency (CEE) Tier 1 and Tier 2 standard save "substantial" amounts of water; Tier 3 machines don't save as much but Cadmus figures that's because they are usually running larger loads. CEE Tier 1 standards for energy efficiency are roughly the equivalent of Energy Star criteria. (Tier 2 and Tier 3 offer tougher standards.)
- Consumers should expect the most efficient clothes dryers to use about 12 gallons of water per load.
- The average amount of energy used by washers in the study was 0.20 kilowatt-hours per cycle; the average electricity used by a CEE Tier 1 efficiency dryer is 2.63 kilowatt-hours. The study found that approximately 82 percent of the energy used per load of laundry came from the clothes dryer versus 13 percent for heating the water and 6 percent for running the washer.
- Spin settings make a difference for energy efficiency results. More efficient washers will spin at faster rates than previous technologies. HOWEVER, a Tier 1 washer will use less energy on the slow spin setting than a Tier 3 washer set on the medium setting. Go figure. So knowledge of spin cycles would be useful.
- Automatic sensors can help make sure that dryers don't run longer than necessary, which will have a big impact on energy consumption.
- Many advanced (aka "smart") clothes washers will use a small amount of energy during the standby mode that will add up over time. That's the downside to the automation and awareness they bring to the clothes laundering process.