Engineers have done a fantastic job of reducing the electricity requirements in the past couple of decades. In many cases, appliances use one tenth (1/10th) the electricity of older versions of appliances. Buying new appliances can thus save you a lot – or sometimes a little in $ and greenhouse gases, depending on which appliance you change. This page shows the approximate electrical load of older and newer appliances. This proves you can buy yourself into a greener lifestyle.
However, there is an alternative – installing solar on your roof or purchasing clean energy from a clean energy provider. This will clean half, most, or all of your greenhouse gases, depending on your choice and/or subscription.
Another possibility is to purchase energy efficient appliances. The table below demonstrates, for various appliances: where most home appliances currently are (second column) and where new state-of-the-art appliances rate (third column). The far right column shows potential savings in kilowatt hours (kWh) and greenhouse gas equivalents and is listed in metric tons = tonnes. This column’s ranges assume lowest and highest values in Column 3. To start, it is a good idea to closely look at column 2, which estimates the percentage (%) of where most home electricity is spent.
Your actual kilowatt (kW) hours may be:
- estimated on an attached EnergyStar sticker; or
- measured with a kill-a-watt (for lower voltage/amp appliances)
To Calculate:
Units and Abbreviations: lbs is an abbreviation for pounds, kg is an abbreviation for kilograms, both are units of measurement of weight. kWh = Kilowatt hour, a unit of measurement used by electricity providers to measure electrical use. Ton refers to a metric ton, or tonne. GHG = Greenhouse Gas.
- Greenhouse gas Savings = (Column 3 – Column 2) * 1.28 lbs CO2/kWh => lbs CO2.
- A lbs->kg converter can convert to kg. 1000 kg = 1 metric ton.
- A metric ton “tonne” is 2200 lbs and 200 lbs greater than an imperial ton.
| % Avg. Energy Use per Home Traditional kWh | State-of-the-Art: EnergyStar ‘Most Efficient’ Source: U.S. www.energystar.gov | Reduced GHG with More Efficient Device | |
| Heating, ventilation and air conditioning | 46-47% total 10,200-23,400 kWh/yr In northern states: 29% heat 17% cooling | Heat pumps can replace furnace and central air conditioning, very efficiently. EnergyStar Furnaces rate to 98-99% efficient: natural gas or propane gas | |
| Water heating | 14-21% (U.S. govt: 20%) 4860-5400 kWh/year | Estimated to use 70% less energy and to save $550/year for family of 4. Heat pump water heater: 1213 kWh per year | 4668-6912 lbs GHG 2117-3135 kg GHG = 2-3 tons |
| Lighting | 8-12% 1 100W Incandescent = 72 kWh/yr. Multiply by no. of light bulbs Lumens Incand. Halogen 375 25 20 800 60 45 1600 100 90 | Lifetime: Incandescents last 1,200 hours; CFLs 8000 hours; LEDs last 50,000 hours each. CFL LED 4 13-15 6-8 23-28 16-20 | NOTE: LEDs are 25% more efficient than discontinued fluorescents; replace with T8 (1 inch) or T12 (1.5 inch) LED according to fluorescent diameter. |
| Refrigeration | 4-5% 1200-1944 kWh/year | Bottom Freezer: 12.8 ft3: 295-386 kWh/yr 16.1 ft3: 355-438 kWh/yr 28 ft3: 595 kWh/yr Top Freezer: 17.5 ft3: 333-448 kWh/yr 20-21 ft3: 371-477 kWh/yr Side-by-Side: one product rated “Most Efficient” 27.4 ft3: 546 kWh/yr | Assumes 300-500 kWh/yr: 1152-1848 lbs 523-838 kg = 0.5-0.8 ton |
| Cooking | 3-4% 680-1440* kWh/year * assumes 1 hr/day each: oven, stove | Induction: 187-190, 195 kWh/yr Radiant: 195 kWh/yr Coil: 195 kWh/yr | Assumes 190-195 kWh/yr: 627-1594 lbs 284-723 kg =0.3-0.7 ton |
| Electronics, Entertainment | 3% 660 kWh/year (assumes 5h TV/day and 6h gaming/week) | ||
| Clothes Washer and Dryer | 3-13% Washer: 900 kWh Dryer: 845 kWh | Front Load Washer: 4.5-5 ft3: 74-120 kWh/yr; 3452-4900 gallons/yr No Top Load Washers rated Most Efficient 5-5.7 ft3: 110-150 kWh/yr 4700-6087 gallons/yr Dryer: 4 ft3: 125-154 kWh/yr 4.5 ft3: 217-245 kWh/yr 7.8 ft3: 266-460 kWh/yr | Washer assumes 75-150 kWh/yr: 960-1056 lbs 425-479 kg Dryer assumes 125-460 kWh/yr: 493-922 lbs 224-418 kg =.65-.9 ton (for wash & dryer) |
| Room Air Conditioner | 800??? kWh Varies by size, age. | 12,000 Btu: 592-600 kWh 10,000 Btu: 470-500 kWh 9000 Btu: 415-422 kWh 8000 Btu: 375-414 kWh | |
| Dishwasher | 2% 600 kWh/year | Max Place Settings = 12 225 kWh/yr; 2.36 gallons/cycle Max Place Settings = 16 210-225 kWh/yr; 3.2 gallons/cycle | Assumes 225 kWh: 557 lbs 253 kg =1/4 ton |
| Computers | 1% | Battery-operated laptops are more efficient than desk-tops; both are low in power. Gaming equipment has higher electricity requirements. |
The Energy Star ratings shown qualify as EnergyStar “Most Efficient”, except where noted.
Sources for Column 2:
- Energy Efficient Homes for Dummies
- GreenLogic Energy: https://greenlogic.com/blog/the-top-5-biggest-users-of-electricity-in-your-home
- Wisconsin Energy: https://www.we-energies.com/savings/tips
- https://www.voltlighting.com/learn/lumens-to-watts-conversion-led-bulb
- Comparison Chart: LED Lights vs. Incandescent Light Bulbs vs. CFLs, https://www.usailighting.com
Electricity accounts for 25% (U.S. including commercial) or 5% (worldwide) of GHG, with residential heating accounting for an additional 6%. My personal experience is that making a home more energy efficient also brings down electricity use.
Heat Pump
Older furnaces may run to 70-ish% efficient; increasing to 80 and 90% efficient with condenser (Amann et al., 2012). The most efficient furnaces operate at 98% efficient. However, heat pumps operate well above 100% (furnace) efficiency but do require an air duct system for air distribution.
An air-source heat pump operates similar to a refrigerator in that it removes hot air from within the appliance. A heat pump can remove heat from the air, thereby cooling it and replacing a central air conditioning system. In addition, it can remove coolness from the air, thereby warming it and replacing a furnace. These are rated using a Heating System Performance Factor (HSPF). An HSPF rating of 10 delivers 3 kWh of heat for 1 kWh, providing an efficiency of 290% (Harley, 2012). Ground-source heat pumps are also available, but less common.
Heat pumps traditionally operate well down to 40-45° F, but few models operate well below 30°. Therefore, many are not recommended for cold temperatures, unless paired with a regular furnace. With advanced technologies, it is possible to select one to use with colder winters.
Air Conditioning
Increases in solar heat arise from solar radiation (sun through windows, skylight, roof), internal home gains (through cooking, showers, people, appliances) and air leakage (ducts and house leakages) (Harley, 2012). It is best to reduce the need for air conditioning first, addressing the three sources of heat gain: sealing ducts and leaks, improving attic and wall insulation, using a ceiling fan, installing a light-colored and solar-reflective roof, upgrading windows, and/or shading externally (best) through awnings, shutters, trees, trellises; and/or internally, through cellular or lighter shades.
In addition to cooling, air conditioners also dehumidify air for comfort and air quality. Using exhaust fans for cooking and baths/showers helps to remove humidity caused by internal gains.
If an air conditioner is 20 years old or older, a new device will be cost-effective. It is best to buy as efficient as possible. Central air conditioners are rated using Seasonal Energy Efficiency Rating (SEER), which measures British thermal units (Btu) per hour of cooling output per watt input (Harley, 2012). Room air conditioners are rated with Energy Efficiency Ratio (EER), which contrasts slightly lower than SEER (Amann et al., 2012). Higher (S)EER values are more efficient, but recommended standards differ between northern and southern climates.
Other systems include (Amann et al., 2012)(Harley, 2012):
- A (ductless) minisplit heat pump has a high purchase price to cool 1-2 rooms, but may cost 1/3 to ½ as much in operation.
- Evaporative coolers are useful in hot, dry areas such as the southwest U.S. They can lower temperatures by 30° by sending outside air through moist pads generating evaporation of cooler air, via fans.
- Economizers are sophisticated air conditioners that select air from outside when outside is cooler and dryer than indoors. Of course, this can be done manually through opening and closing windows at opportune times.
- A whole house exhaust fan can cool a house in minutes, when it is cooler outside by blowing air into an unconditioned attic or outside.
Hot Water Heater
Water heaters have improved in their efficiency considerably; older water heaters may cost as much as or more to operate than recent furnaces or air conditioners. Three common water heaters include storage tank, on demand, and the newest, heat pump. An Energy Factor (EF) rates their efficiency and applies to all three types. On demand are generally only installed in remote locations where they cannot operate on a storage tank. Heat pump water heaters save considerably in operational costs (1/3 to ½ as expensive), but do not operate well outdoors in cold temperatures. They need sufficient warm air around them and exhausted air is cool and dry (excellent for basements) (Harley, 2012)(Amann et al. 2012).
The consumer product safety commission recommends setting water heater temperatures to 120° F. Using water heater temperatures above 120° F risks scalding and costs 2-5% more for each 10° increase. Lower water temperatures also lengthen the water heater’s lifetime, by reducing scaling and corrosion. However, setting a water heater temperature below 120° F increases the risk of legionella pneumonia (Harley, 2012). To estimate your water temperature, test hot water temperature after an hour of no hot water use, then run water until hot. The thermometer should be able to test to temperatures of 150° or greater.
Adjusting the temperature properly may best be done by a professional. For electrical water heaters, turn off the heat first, then adjust two likely thermostats, one for each heating element at the bottom of the tank (Harley, 2012). For gas water heaters, the thermostat is located by the gas valve; markings must be analyzed and interpreted correctly to adjust.
A heater system’s first-hour rating evaluates how long it takes to turn a cold water tank into a hot water tank, assuming you use hot water up. When buying a new water heater, estimate tank size requirements according to your peak demand hour, considering that a shower is estimated at 20 gallons/person/hour, and a manual dish wash may be 4 gallons/hour (Amann et al., 2012). Installing insulation for the first 10 feet of hot water pipes is recommended. The best way to conserve water is to use efficient low-flow kitchen and bathroom faucets, shower heads, and toilets. (See Optimizing Water Use.)