Lennox G51 Furnaces | FurnaceCompare®

Lennox G51 Furnace Overview

The Lennox G51 gas furnace is one of Lennox’s higher-end furnaces and part of their Elite Series. The G51 is Energy Star qualified by the Environmental Protection Agency. All models of the G51 have a rating of 92.1% AFUE. Lennox estimates that users of the G51 can expect between $2088 and $3378 in savings on their utility bills over 3 years when compared to 55%-65% AFUE units.

The furnaces have an insulated cabinet, which the company claims reduces a unit’s sound. The G51 also has two heat exchangers – an aluminized steel one and a stainless steel secondary one, which capture more heat thus adding to efficiency, according to Lennox’s product brochure. Like other Lennox Elite Series furnaces, the G51 can be used with an electric heat pump to increase fuel efficiency.

Furnace Filters for the Lennox G51

Air Flow Configuration Cabinet Width Filter Size(s)
All 17-1/2″ 16x25x1 (bottom)
All 21″ 20x25x1 (bottom)
All 24-1/2″ 24x25x1 (bottom)
All All 16x25x1

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Consumer Reviews of Lennox G51


  • Very Satisfied
  • Somewhat Satisfied
  • Neutral
  • Somewhat Unsatisfied
  • Very Unsatisfied
  • #1 of 29 Lennox Furnace
  • 66.67% of customers recommended

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Lennox G51 Furnace Reviews


1.0 rating
Very Unsatisfied

Then with a tornado in Iowa no parts for three months!! Middle of January in Minnesota under warranty what’s that going to do then blame company installers? Joke it�s truly not the Callalac of furnaces… Stay the hell away from Lennox joke

Woodbury, MN

"Highly recommend this over the G61 model"

5.0 rating
Very Satisfied

R. G. Wahl of Saline Michigan installed this for us in April of 2009 under warranty, replacing the g61 model that we had for one year – a review has been submitted for this model, of which the major complaint was the noise of the two stage blower motor. There were other complaints on that furnace as well, but the only thing I can remember was the blower motor. Now, the G51 furnace has been perfect… except for a rare occurrence, which has so far been easily resolved. It seems that whenever we return from havng been away for an extended period of time during the winter, the first night back when we turn up the thermostat, the furnace will turn off. The solution has been to reset the furnace, and it comes back on and works without another issue until we again return from an extended trip in the winter time. When we report the problem the next morning (it always happens at night, as that is when we return), we are asked for the error code that was flashing before we reset the furnace. We never remember to write this down. Probably because we are half asleep, and there is no paper and pen in the furnace room. So, as of now there is no solution, due to our own neglect in not writing down the code. But other than that, no problems in 3-1/2 years.

Saline, MI

"Lennox High Efficiency Furnace Lives up to its Reputation"

5.0 rating
Very Satisfied

I’ve had this Lennox G51 single stage high efficiency furnace (92%) for four years. It replaced a furnace that was installed in about 1970, which was probably no better than 65% efficient. Obviously I am extremely pleased with the savings in fuel (both cost wise and environmentally). It is quiet and moves air well, keeping the house evenly warm in winter without the drafts caused by the previous furnace (which did not regulate its temperature well, in that it kept blowing air that was not heated, and took a long time to come on as the temperature dropped). This Lennox furnace, however, seems to respond in a very sensitive way to the changing temperatures in winter and comes on when needed and turns off before cold air starts blowing. I have never had any problems with the furnace at all except the second time I turned it on after installation. The installers returned and found a mistake in their own electrical wiring, but nothing wrong with the furnace itself. I would definitely recommend this furnace to others looking to upgrade to a product that is more efficient. It has definitely been a good value.

Detroit Michigan

Other G51 Reviews

Feedback from online forum sites about the G51 seems to be mixed. On HVAC-Talk.com, one poster says that it is the most reliable furnace on the market while others point out some of the issues with materials used in the G51.

Lennox G51 Model Numbers

The G51 is available in different models which vary in efficiency and capacity.

Model Number AFUE BTUs per Hour
G51MP-24B-045 92.1 44,000
G51MP-36B-045 92.1 44,000
G51MP-36B-070 92.1 66,000
G51MP-36C-090 92.1 88,000
G51MP-48C-090 92.1 88,000
G51MP-48C-110 92.1 110,000
G51MP-60C-090 92.1 88,000
G51MP-60C-110 92.1 110,000
G51MP-60D-135 92.1 132,000

G51 Warranty

The G51 is covered by a limited lifetime warranty on heat exchanger parts and 10-year warranty on the compressor. Lennox also offers a 5-year warranty on other components.

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