Just about everything said about new furnaces can be applied to new gas- and oil-fired boilers. They're smaller, more efficient (some have AFUE ratings similar to those on furnaces), quieter, and more sophisticated, and some have variable-capacity burners.
High-end boilers offer sealed combustion, which eliminates the consumption of house air burned up and vented outside when the burner fires. Sensors mounted outside the house can record the temperature and adjust the boiler's water temperature to the conditions outdoors.
Features like these make boiler installation more expensive and the systems more complex but also much more energy-efficient than previous models.
So what should you do about replacing your old furnace or boiler? Because every house and every situation is different, it is impossible to say whether or not a replacement furnace or boiler would make good economic sense for you. But if you have a large house, if you live in a cold climate, or if the price you pay for gas or oil is high, the scale tips in favor of the higher-efficiency models.
If your house is small or you live in a temperate climate, paying a premium for a super high-efficiency furnace makes less sense from a strictly economic standpoint. In that case a less expensive two-stage or variable-speed furnace or a simpler boiler might be the better value. A quality HVAC installer will take time to analyze your specific situation and can recommend the best options for your needs and budget.
Remember to consider the actual cost of heating your home -- not your entire energy bill -- using the simple calculation spelled out earlier in this chapter. At some point, if your heating bill is relatively low to begin with, the savings difference between an 80-percent and a 95-percent furnace doesn't amount to enough to make the larger investment worthwhile.
Also, check into whether your utility company or state energy office offers a rebate toward higher-efficiency heating and cooling equipment. Some do, and the amount tendered can sometimes pay the difference between a lower and a higher-efficiency model.
Whatever you decide, if you do opt for a new furnace or boiler, be sure you are satisfied with the skill and integrity of the installer before you hire out the work. The quality of the installation matters most. Sloppy or careless work on even the best brand of HVAC equipment will result in a less-than-ideal setup that might require repeated call-backs and more time than you're willing to spend.
Be sure the installer makes a thorough energy audit of your house before you start talking about a specific furnace or boiler. One key component in how well HVAC equipment performs has to do with whether or not it is sized correctly for the anticipated heating load. Such factors as window size, number, and placement; attic and sidewall insulation; square footage of habitable space; and other items need to be accounted for in a sizing calculation. Installers use what is called a Manual J spreadsheet to arrive at the correct heat load, and from that they can recommend an ideal size furnace or boiler.
Be sure, too, if you have plans to increase the size of the house (for instance if you're going to add an addition) or its heating space (a finished basement perhaps) that the contractor knows of these impending larger demands on the heating system so it can be sized accordingly. The boiler or furnace capacity must properly fit the space it will heat. Otherwise, it will run inefficiently, might cost more than it should, and won't provide the comfort it was designed to deliver.
Replacing the Air-Conditioning Unit
Air-conditioning compressors are rated by their seasonal energy efficiency ratio (SEER) numbers. SEER designates the efficiency you can expect from your air-conditioning system. Higher numbers mean better efficiency. Federal regulations now mandate better energy conservation: As of 2006, only air conditioners rated 13 SEER and higher are available. If you have an older A/C compressor that you typically run a lot during the summer and you own a large house, purchasing a higher SEER unit could make economic sense.
Here's an example of how a replacement upgrade can save electrical energy and money: An older 10-SEER air conditioner requires 1,200 watts of power to produce one ton of cooling (12,000 BTUs). Every point upward results in approximately a 5 percent increase in energy efficiency. A 15-SEER rated A/C unit would consume only about 800 watts to produce that same one ton of cooling.
So, if you have a three-ton capacity A/C unit (a relatively common size), and your electrical cost is 12 cents per kilowatt-hour, the older 10-SEER unit will cost about 43 cents if operated continuously for an hour. (1,200 watts x 3 equals 3,600 watts. 3,600 watts divided by 1,000 equals 3.6 kilowatt-hours x 12 cents equals 43.2 cents).
Running a 15-SEER A/C of the same capacity for the same amount of time would cost 28.8 cents. (800 watts x 3 equals 2,400 watts. 2,400 watts divided by 1,000 equals 2.4 kilowatt-hours x 12 cents equals 28.8 cents.) That 14.4-cent difference for every hour of operation could add up to substantial savings over the course of a hot summer. And bear in mind that, due to deterioration and inefficient design, many A/C systems ten years old and older may be operating at only 6-9 SEER.
The highest-efficiency central A/C units on the market today are rated at about 17-18 SEER.
Quieter While Operating
Another advantage of new A/C units is that they run more quietly than previous models. This can be an important factor if you spend time outdoors around your house or if you have nearby neighbors. It's also important if you have bedrooms located close to where the outdoor compressor is situated.
Variable Speed -- Two Stage
As A/C units evolve and become more efficient, engineers devise new ways of making them work harder to achieve better comfort. One recent innovation is to equip air conditioners with two-stage compressors, which are somewhat similar to a two-stage furnace. On warm -- but not hot -- days the compressor runs using only the lower stage.
This provides adequate cooling, but the compressor runs more quietly and for a longer period of time, which gives the system more of an opportunity to remove moisture from the air. The lower the humidity indoors, the higher you're likely to set the thermostat, which results in energy savings.
Variable-speed blowers alter the speed of the blower motor to most efficiently match the output of the air conditioner's compressor and condenser. This translates into better use of the available amount of cooling, less electricity consumption, and lower energy bills.
Like a heating system, a cooling system has to be installed correctly and sized accurately in order to work well and maintain the efficiency for which it was designed.
For years it was common for installers to place oversize air-conditioning units in homes in order to avoid claims of insufficient cooling in the summer. This practice means an air conditioner runs for short periods of time on many days, cools the house off rapidly, and then shuts down until the thermostat calls for cooling again. The result is a home that cools quickly but doesn't run air through the evaporator coil in the furnace long enough to achieve good dehumidification -- in other words, a cold but clammy house. Homeowners respond by turning down their thermostats to the point that dehumidification does take place, but at the expense of keeping the house much cooler than it needs to be.
Installers now use computer software to incorporate such information as window size and placement, insulation found in attics and sidewalls, square footage, orientation and geographical location of the house, and other factors into their sizing calculations. This enables them to precisely determine which air conditioner suits a particular house. In addition, two-stage and variable-speed A/C systems are capable of adapting themselves to provide just the right amount of cooling and dehumidifying needed for virtually any situation.
In the next section, we'll take a look at replacing your plumbing in order to improve home energy efficiency.