Hot Stuff! Or, Your Home’s Oil Heating System and Its Replacement

• barrieabalard
• December 10th, 2009

Two points that I forgot to mention last week. First, both natural gas and propane heating systems carry the risk of carbon monoxide poisoning, so be sure to have sufficient CO monitors in your home, especially if your heating system is not a relatively new one. (It is my understanding that you always need CO monitors in your home if you use propane regardless of the system’s age.) Newer natural gas furnaces have multiple safety devices and electronic sensors that make it next to impossible for CO to escape into your home. Oil systems generally don’t have as many problems with CO because the furnace is stronger, but if yours is older, it’s wise to install the CO monitors. Electric systems do not have the risk of CO, but wood, coal, and kerosene stoves all carry CO risk. Vent them properly and use monitors.

Second, you can figure out the AFUE (Annual Fuel Utilization Efficiency) number for your gas or oil heating system by identifying its equipment features as follows:

Old, low-efficiency heating systems have:

• Natural draft that creates a flow of combustion gases
• Continuous pilot light
• Heavy heat exchanger
• 68%–72% AFUE

Mid-efficiency heating systems have:

• Exhaust fan controls the flow of combustion air and combustion gases more precisely
• Electronic ignition (no pilot light)
• Compact size and lighter weight to reduce cycling losses
• Small-diameter flue pipe
• 80%–83% AFUE

High-efficiency heating systems have:

• Condensing flue gases in a second heat exchanger for extra efficiency
• Sealed combustion
• 90%–97% AFUE

(Source:  U.S. Department of Energy)

Oil furnaces (forced hot air heat) and boilers (hot water heat), as well as a quick look at alternative heat sources, are today’s focus. I’ll start by pointing out that you can use the same AFUE chart in last week’s blog entry for oil heaters as well as gas heaters. Use the chart and process I described to figure out the ROI and length of payback when you install a newer, more efficient system. In general, replacing an oil system with an oil system costs more than replacing a natural gas system with a gas system.

As I mentioned last week, with gas furnaces, any system that’s older than twenty years is worth replacing if you have the cash to do so, and if you plan to live in the home for several more years. Note that hot water systems, which use boilers instead of furnaces, are often good up to twice as long (but do check with your heating system repair person if you have any doubts). If your furnace uses oil, however, it might not need to be replaced as quickly as a gas furnace of the same age. Twenty-year-old oil furnaces usually offer better energy efficiency than comparably-aged gas furnaces.

So, when do you replace? If your current heating system is one of the following types, replacement should be considered:

• Old coal burner that was previously switched over to oil or gas
• Old furnace without electronic ignition. If it has a pilot light, it was probably installed prior to 1992 and has an efficiency of about 65% efficient (the least efficient systems today are 80%)
• Old furnace without vent dampers or an induced draft fan (which limit the flow of heated air up the chimney when the heating system is off).

(Source:  American Council for an Energy-Efficient Economy)

Of course, if your heater needs frequent repair or is inadequate for the job of heating your home, you might want to replace it even if payback time for costs or return on investment doesn’t save you money.

Here’s something interesting to consider when thinking of replacing an oil furnace that has an AFUE of 60 or lower. You could upgrade your system with a newer, standard-efficiency flame-retention head burner. These often have an AFUE of around 80, and probably would be cheaper than replacing the entire oil furnace. See this explanation for more about what a head burner is, and why the flame-retention kind is superior. For the most energy efficiency, however, you will need to replace the entire heater.

If you are using an alternative source (wood, coal, solar, wind, etc.), replacing your system can be as inexpensive as buying a new wood stove, or it can be quite costly. While I applaud using alternative sources, I will not cover the replacement costs for these systems at this time. Also, unless the heat source is connected to your ducting with a fan to move the heat around, you won’t have central heat.

I will point out an alternative that you can try with minimal cost—using electric space heaters to augment your central heating system if you can’t currently afford to replace it. We save on energy costs by running the thermostat much lower when we use space heaters. Four of them cost us about ninety dollars. I move mine around as needed during the day. I hate to be cold (twenty-five years in Massachusetts will do that to you) and we live in a largeish, drafty home, so the space heaters have worked out well. I run mine to warm up the bedroom before going to sleep, then turn it down. We are saving fifty to sixty dollars a month total on energy costs, so the heaters paid for themselves in less than two months. And that’s with the high cost of electricity in New Jersey.

Next week: more on costs, changing to a different fuel source, another look at alternative fuels, and a linkfest full of information.

Tickers: alternative fuels, calculating payback time for new heating system, carbon monoxide (CO), electric space heaters, heating systems, oil heating system replacement costs, propane heating systems

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