The average American household spends $635 on heating, per year (EIA, 2011). This amount increases to $1.000 or more, in colder regions. Heating costs - mostly associated to central furnace systems, in America- are by far the most important energy cost in many countries worldwide (in the UK, the average heating bills are higher than in the North America).
A furnace with an AFUE of 90% will waste about 10% of the heat in the gas, oil or pellets, besides other possible losses through the venting system and the ducts, or due to poor maintenance.
Furnace heat losses amount to about 40% in most homes.
But the heat loss through walls, ceilings and floors is not smaller than the loss mentioned above. And that allows experts to say that most of the heat produced by a furnace (or by other heating system) is to replace heat that is lost through the chimney, the walls, the attic, the air leaks...
The bottom line: before buying a furnace you should seal and insulate your home. Ideally, you should insulate and seal it to very high levels, to keep heat loss to a minimum. That's the approach of super-insulated homes, and a way of replacing central furnace systems with gas wall furnaces or other space heaters - the best way to reduce heating bills to a minimum.
Gas furnaces are becoming standard, while oil furnaces are losing their market share quickly. And that speaks for itself.
Electric furnaces are too expensive to operate, and they are morphing into heat pumps. New wood pellet furnaces have little in common with traditional midwest furnaces, but the most sophisticated models are expensive and their results very mixed.
Installation costs are typically higher than the equipment; if you have to replace the ductwork, or re-line and change the chimney and venting system, that can be more expensive than the furnace itself.
Performance is important. And we recommend a 90%+ AFUE (Annual Fuel Utilization Efficiency) furnace for comfort and performance. A 90% AFUE furnace will lose 10% of heat during the combustion process, while a 80% AFUE furnace will lose 20%...
Take into account the Energy Guide label attached to the furnace, and prefer a multi-stage and variable speed unit, with sealed combustion. These furnaces provide more comfort, less drafts, less noise, a quicker heating and energy savings.
Their problem: they are a lot more expensive.
Features like zoning (room-by-room heating) can be important, in large buildings. Why should you heat rooms that aren't being used? Multi-stage variable speed furnaces allow you to heat a room quickly, when needed, and that –combined with zoning – is important for energy savings.
Temperature zoning is the only way of improving the energy efficiency of a central heating system, and that’s great in large homes where alternatives to central systems are difficult to implement.
But it requires some conditions. The success depends on how the system is used or on issues like insulation and air sealing, to minimize heat losses and to reduce the difference in temperatures between the rooms that are being heated and those that aren't.
Do not overlook the maintenance of your furnace. Poor maintenance will cost your many hundreds of dollars during the lifetime of your furnace, and surely much more than the costs of a regular professional maintenance.
You may carry out yourself some basic maintenance, which is important and rewarding, but that doesn't replace professional maintenance. Gas furnaces should be professionally maintained every two to four years, and oil furnaces every year.
Prefer a sealed-combustion furnace. Furnaces emit significant amounts of CO2 (and CO, a deadly gas, and water vapor and other pollutants).
If you have a traditional furnace, without non-sealed combustion, consider a CO detector. These detectors are cheap (often between $20 and $30) and can prevent serious hazards and save lives. Mount one in each level of the house. For models and customer reviews in Amazon, see: CO Detectors.
Look for signs of soot and odd odors. Call a technician if you detect any signs.
Furnaces have a very significant environmental impact. Each furnace emits on average 20.000-50.000 pounds of CO2 per year. Reducing such amounts by 30% - which is easy to get through conservation measures or by upgrading to a new multi-stage variable speed 90%+ AFUE furnace – is equivalent to reduce the CO2 emissions by 90.000-100.000 pounds over the expected lifetime of the equipment (20 years or more).
Also consider the super-insulation approach, if you are planning to build a new home or a major renovation. It can be a way of replacing central ducted furnaces with low-emission heating systems.
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