Furnaces/Heat Source
Most homes in the Portland area are heated with natural gas combustion furnaces. Some homes use oil furnaces and most of this information will apply to those units as well.
Furnaces have different levels of efficiency which is measured in an Annual Fuel Utilization Efficiency rating (AFUE). The rating measures the furnace's ability to extract heat from the combustion process, higher ratings are better. Old combustion heat systems including older oil burners and gas furnaces with pilot lights and/or ribbon burners have AFUE in the 60-75% range. The most common furnaces in our area are "Mid-Efficiency" furnaces with AFUE of 80-82%. High efficiency furnaces which have AFUE of 90-96% are growing in popularity with the rapid increases in the cost of natural gas.
Clearly there is a significant difference in the natural resources used by a 70% furnace versus a 95% furnace, and as the price of gas continues upward the value of that improved efficiency rises with it.
Old oil burning furnace Mid efficiency gas furnace High efficiency gas furnace
Furnace Efficiency
The AFUE rating is not always visible on a furnace. Look for the yellow Energy Guide sticker (visible on furnace at right) which lists the rating. Also some model numbers will incorporate the AFUE such as "80, 90, 92, or 95". Some furnace covers may say "high efficiency" but not be considered so by today's standards. All new high efficiency furnaces are what are called "condensing" furnaces. These units extract so much heat from the combustion process that the exhaust gases are cooled to the point where condensation occurs and creates water as a by product. For this reason, a tell-tale sign of a high efficiency furnace is that the exhaust gases are vented with plastic pipes (right hand furnace) instead of a metal vent (left and middle furnace). Additionally a high efficiency furnace has a small pump, about the size of a shoebox, that usually sits on the floor next to the furnace and intermittently pumps the condensation water to a drain, sink, or the exterior.
A heating contractor can perform a "combustion analysis" on your furnace that will give a real-time AFUE rating and can be very helpful information when deciding whether or not to replace an older furnace.
Thermostats: The Ultimate Energy Saving Tool
The fastest way to immediately cut your home energy use is to turn down your thermostat. Put on a sweater, put on a hat, and tough it out. Turn it down when you leave the house and turn it down when you sleep. Your savings will be huge!
Unfortunately it can be hard to get everyone in a household on board with the "low temperature" plan, and thermostat wars are a well known phenomenon to most couples. A great solution is a Programmable Thermostat. This device will allow automatic, scheduled operation of the furnace through different times of the day and different days of the week. And if unscheduled heat is needed, just push up the heat for a temporary override.
Debunking the "Re-Heat Myth" (from the U.S. Department of Energy)
"A common misconception associated with thermostats is that after a temperature setback, such as in the morning, a furnace has to work harder (e.g. burn more fuel) to warm the space back to a comfortable temperature, thereby resulting in more energy consumption rather than less. This misconception has been dispelled by years of research and numerous studies. The fuel required to reheat a building to a comfortable temperature is roughly equal to the fuel saved as the building drops to the lower temperature. You save fuel between the time that the temperature stabilizes at the lower level and the next time heat is needed. So, the longer your house remains at the lower temperature, the more energy you save."
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