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Building Science

Should the DOE Increase Furnace Efficiency Standards?

The battle over minimum furnace efficiency continues with a new proposal to go to 92 AFUE

The U.S. Department of Energy has proposed a new efficiency standard of 92 AFUE or greater for furnaces. This standard will eliminate atmospheric combustion furnaces, and furnaces that meet the new requirement, if passed, will look like the one here and have plastic intake and exhaust pipes.
Image Credit: Energy Vanguard

Do you know when the U.S. last raised furnace efficiency standards? It was 1987. Do you know how long the U.S. Department of Energy (DOE) has been trying to change that? At least since 2007.

The past eight years have been a sad case of industry heavyweights preventing progress on this important issue. The DOE, however, just proposed a new rule, so we might finally see some action here. Do you know when it’s set to go into effect, if passed?

A bit of furnace efficiency history

In 1987, the National Appliance Energy Conservation Act set a minimum of 78% Annual Fuel Utilization Efficiency (AFUE). That’s when furnaces with standing pilot lights went away.

In 2007, the DOE proposed raising the minimum from 78 to 80 AFUE. What?! Yes, it’s true. They really did that, even though the rule would have had pretty much zero effect on saving energy.

Why? Because even though 78 AFUE was the minimum allowed, nearly every furnace being made is 80 AFUE or higher. I think I’ve seen only one new furnace that had an AFUE lower than 80.

So the battle began. The state of California and a coalition of environmental and energy efficiency groups sued the DOE. That led to a set of regional standards, whereby Northern states (those with more than 5,000 heating degree days) would have had to go to 90 AFUE and the warmer South and Southwest would get to stick with 80 AFUE.

And that’s when the American Public Gas Association (APGA) blew up. According to the American Council for an Energy Efficient Economy (ACEEE), the APGA “argued that consumers would flock to electric resistance furnaces rather than install high-efficiency gas furnaces.” (See their article, Why DOE’s Cave on Furnace Standards Is Such a Big Deal.)

There’s no way they really thought that would…

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4 Comments

  1. User avater GBA Editor
    Patrick McCombe | | #1

    Orphan water heaters
    What about the problem of the orphaned water heater when someone switches to a direct vent NG furnace? Now with only one appliance venting into a flue that used to vent two, these flues are almost always oversized, which causes the water heater's flue gasses to spill into the space where the heater is located. In addition, high-efficiency furnaces are way more complicated and repair parts are more manufacturer specific, so they're harder to find when the furnace breaks. And what's the payback for a new furnace with a 10% efficiency boost. My guess is decades. I'm not convinced that we should require folks to install 90+ furnaces. Of course they should have that option, but a requirement--I don't think so.

  2. User avater
    Dana Dorsett | | #2

    get rid of that orphan too... (for Patrick McCombe)
    Atmospheric drafted combustion appliances are more trouble than it's worth, especially now that new houses have to test a sub-3ACH/50 to meet IRC 2012 code, the back drafting potential becomes huge. Just get rid of them all- insist that combustion equipment (whether water heaters or space heating equipment) all be direct vented/sealed combustion going forward as a matter of public health.

    Venting an atmospheric-drafted water heater into a flue shared by a higher-BTU/hr furnace or boiler was always a pretty sketchy hack in the first place. Space heating loads in IRC 2012 code-min houses are now comparable to or lower than the burner output of a hot water heater, if they were right-sizing the space heating equipment to the actual loads the flues would all need narrower liners anyway.

    Whether the DOE minimum AFUE is 80%, 90%, or 92%, requiring that the equipment never be more than 1.7x oversized for the load (the presumptive oversizing factor in the AFUE test) or less than 1.25x (to be able to utilize overnight setback strategies) would be the right thing for both comfort & cost. Equipment sizing is not within the DOE's regulatory domain, but very few states put a limit on oversizing factors, and the result is rampant 3-5x oversizing "...just in case..." there is a cold snap that takes the outdoor temps down to -150F or -225F or something.

    The "payback" on right-sized sealed combustion equipment is immediate, in the form of lower noise, stabler room temps, less wind-chill,. less backdrafting potential etc. If it happens to be condensing equipment, great. Payback on the cost difference on fuel savings alone may take decades at 50 cents/therm residential retail rates in warmer climates, but the notion that we are pre-destined to have prices this low is a dubious assertion at best, subscribed to primarily by those drinking the frack-water.

    About 25% of all natural gas production in the US is by-product from light-tight oil shale fracking, and at current wholesale oil prices the drilling rate for new production has slipped off a cliff, since it's uneconomic. A fracked oil well is pretty much depleted within 3 years of it's initial production, on average- it's only a matter of time before the production slips over the same precipice. At the same time utility companies are falling all over themselves installing combined cycle gas generating capacity to replace retiring coal plants, since the thermal efficiency is about 2x that of the sub-critical thermal coal they are replacing, and they have much better ramp rates, allowing them to do most of the load tracking at much higher efficiency than gas peaker plants. The upshot is increasing net gas use, and a structural setup for declining gas production. Fracked dry gas wells that do not have significant liquids (either light oil, or propane & butane) are not profitable at anywhere NEAR the current wholesale prices for natural gas. To keep gas production up to recent levels will demand a price 3-5x higher than the recent 3-year running average, barring some magic new technology for extracting it.

    Bottom line, gas prices are at historical lows, but can't remain there- they will (as has been true for decades) be volatile. Predicting the fuel cost savings "payback" of 92% efficiency vs. 80% efficiency within a 15-25 year lifecycle for the equipment isn't really possible, and basing it on recent years' gas pricing would be silly, at best.

  3. Doug McEvers | | #3

    Furnace fan electrical usage
    Modern furnaces with DC fan motors use far less electricity than fans of old. This should be part of the furnace efficiency discussion and payback. Natural gas costs may be static but electrical rates continue upward. Lower overall electrical usage due to efficient lighting and other improvements will insure future rate increases.

  4. Keith Gustafson | | #4

    Absolutely the efficiency
    Absolutely the efficiency standards should be increased.

    BE careful however on throwing in 90 percent and 96 percent like it is all the same thing. 96 percent is much more complex. For instance the sheet metal must be thinner on combustion chambers, as stainless steel is a poor conductor and the difference in a .01 thinner steel makes a difference, but can harm lifespan.

    I have a pair of condensing furnaces at work, installed in the 90's for their lack of vertical chimney ore than fuel savings, that run along with no problem day in and day out

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