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Replace incandescent bulbs

SAVINGS:   $6 per bulb per year in electricity savings; 120 pounds of CO2 emissions a year.

WHY:   ~90% of residential lighting comes from incandescent bulbs -- the single biggest inefficiency contributing to wasted energy (thereby CO2 emissions) in the U.S. Addressing this one inefficiency -- lighting -- could prevent 480 million lbs of CO2 emissions, and actually costs less than “business as usual.”

HOW:   Select “Choose A Light Guide” for available CFL types at; target 60-100 watt bulbs used several hours a day to switch -- swap them for 13-23 watt CFLs. Make sure to recycle CFLs at any Home Depot or Ace Hardware.

LED lightbulbs are a little bit more expensive than CFL’s or incandescent lightbulbs, but they are a very smart investment. LED lightbulbs are far more efficient, will drastically reduce your energy bill, and last 2-4 times longer than CFL’s and 40 times longer than incandescent – in the long run, they will save you a lot of money.


Insulate Attics and Walls

SAVINGS:   ~$150 for the attic and ~$200 for walls per heating season; 1,006 pounds for the attic and 3,393 pounds for the walls of reduced CO2 emissions a year.

WHY:   Heating (in conjunction with air conditioning) is the home’s biggest energy consumer at ~45% of a home’s total energy use. Being warmer in winter and cooler in summer makes for a more comfortable home, plus a well-insulated house is quieter.

HOW:   Insulating attics can be a do-it-yourself job, but given the time and headaches it takes to install insulation, it’s almost cost comparable to hire a professional.

Insulating existing walls is NOT a do-it-yourself job. Cellulose insulation can be blown into wall cavities that are at least 3" deep through holes (drilled either from the inside or outside). This is an ideal option for wood-framed homes, and most pre-1976 wood-framed houses have empty wall cavities. Solid brick homes, such as bungalows and Denver Squares, need to fur out the walls in order to add insulation.

Xcel Energy, the Denver Energy Challenge and Groundwork Denver have lists of vetted contractors.


Create an Air Barrier

SAVINGS:   ~$50 per heating season; 571 pounds of reduced CO2 emissions a year.

WHY:   Heating (in conjunction with air conditioning) is the home’s biggest energy consumer at ~45% of a home’s total energy use, and ~$13 billion worth of energy in the form of heated or cooled air escapes through holes and cracks in U.S. residential buildings a year. Insulation generally does NOT air seal, so even a well-insulated house may need air sealing.

HOW:   For the do-it-yourself (DIY) project use caulk, rope caulk, spray foam sealant, weatherstripping, door sweeps/thresholds, window glazing and outlet gaskets:

  • plug gaps around pipes, wiring, ducts and vents that go through barriers separating conditioned air from unconditioned air such as walls, top-floor ceilings and floors above crawl spaces.
  • add weather-stripping to doors and windows.
  • cover old windows with plastic film during winter.

Don’t plug up intentional air ventilation, such as combustion air ducts or flues, or crawl space vents. It is unlikely that older homes could be air sealed enough to create indoor air quality issues, but it’s always a good idea to install a carbon monoxide detector for about $40.

Xcel Energy, the Denver Energy Challenge and Groundwork Denver have lists of vetted contractors.


Replace Inefficient Refrigerators and Retire the Beer Fridge

SAVINGS:   Upgrading to a new, standard-sized Energy Star refrigerator from a pre-1989 refrigerator saves at least $150 a year in operating costs, and retiring a fridge altogether saves even more; 1,000 pounds of reduced CO2 emissions a year.

WHY:   Refrigerators are the biggest energy user (besides the humans) in the kitchen, consuming ~14% of a home’s total electricity use.

Extra refrigerators are generally old. Refrigerators and freezers manufactured today use 30% less energy per cubic foot than similar models did in 2001, and 60% less per cubic foot than models sold in 1980. And fridges in garages or on porches consume even more energy because of the uncontrolled ambient temperatures.

HOW:   Go to to calculate the operating costs and emissions of your current refrigerator(s).

In looking at the myriad options to replace a refrigerator, keep in mind that generally top-mount freezer models without through-the-door ice are the MOST efficient models, and side-mount freezer models with through-the-door ice are the LEAST efficient. Both top- and bottom-mount freezer models tend to cost less and are more reliable than side-mount models.

Tips for reducing your refrigerator’s energy consumption:

  • Position your refrigerator away from heat sources such as ovens, dishwashers or direct sunlight.
  • Leave a space between the wall or cabinets and the refrigerator or freezer to allow air circulation; keep the condenser coils clean.
  • Check the gasket’s seal by closing the door on a dollar bill; replace the gaskets if the bill falls out or can be easily removed without opening the door.

Install A High-Efficiency Furnace

SAVINGS:   $126-320 per heating season in operating costs, depending on former efficiency, use and fuel costs; updating a furnace from 77% to 90% saves 2,304 pounds of reduced CO2 emissions a year.

WHY:   A furnace that is only 65% efficient means 35% -- a third! -- of the heating fuel’s energy escapes up the flue and elsewhere. If the furnace has a pilot light, it is probably ~65% efficient. And heating (in conjunction with central air conditioning) comprises almost half of a home’s total energy use.

HOW:   Install a high-efficiency (also known as condensing) furnace that is AFUE 90-97% efficient. (The higher the “AFUE” number, the more efficient the furnace.)  It is difficult to find reviews on all the various furnaces on the market; generally, it is best to find a reputable contractor first, and then work with the contractor to determine the best furnace for your home. A good contractor will perform calculations to properly size your furnace; don’t just swap out the old one with a new one the same size. If you’ve increased your insulation, air sealed, sealed ductwork, and/or refurbished or replaced your windows, your new furnace should be smaller than the existing furnace. The furnace you select should have at least a 20-year warranty on the heat exchanger and 5-year warranty on all parts.

There are several online resources that provide furnace replacement considerations, figures, and advice, including tips on finding a contractor:

  • U.S. Department of Energy’s Energy Efficiency and Renewable Energy website at

Eliminate Phantom Loads

SAVINGS:   ~$4 per year per gadget; 115 pounds of reduced CO2 emissions a year.

WHY:   ~8% of U.S. household energy consumption is consumed by phantom load, which is purely wasted energy. Radios, chargers, heaters, TV entertainment devices, stereo components, kitchen equipment, hair dryers, electric toothbrushes, computers and peripherals – almost all household appliances that have clocks, timers, memory, remote controls or external power supplies (those boxy plugs) – are consuming electricity even when turned “off.”

HOW:   Unplug rarely used appliances and chargers when not in use.

Power-Strip Hubs: Create power-strip hubs by plugging electronics into easily-reachable power strips, and then switching them off when not in use.

Smart Power Strips: For computer and entertainment systems, use a “smart” power strip, which closes the outlet circuits of peripheral devices when the main device (e.g., TV or computer) is turned off, as well as providing surge protection.

Wall Switches: Plug TVs, stereos or other major appliances into a switchable outlet, and turn off the outlet when the appliance is not in use.


Plant a Tree

SAVINGS:   Over a 50-year lifetime, a tree generates ~$30,000 worth of oxygen, provides ~$60,000 worth of air pollution control, recycles ~$35,000 worth of water and controls ~$30,000 worth of soil erosion; it also sequesters 50 pounds of CO2 emissions a year.

WHY:   Trees lower air temperatures and shade buildings in the summer and block winter winds, so they can reduce building energy use and cooling costs.

HOW:   The Park People provide low-cost street trees (application deadline is every February), and hosts a low-cost tree sale every April through its Denver Digs Trees program.

Denver Water has extensive Xeriscaping resources, including a Xeriscape demonstration garden at 1600 West 12th Avenue. CSU Extension provides growing advice for Colorado’s climate. And the City of Denver’s forestry department provides a list of recommended trees.

Cherry Creek Tree Farms, Arapahoe Acres and TagawaGardens nurseries provide warranties on plant material. Check if your favorite garden center does too.

See also: Energy Audits