Lennox manufactures a wide range of gas and oil furnaces; the product line is divided into a few categories which vary in energy efficiency and price level. As of 2015, the cheapest furnace product range from Lennox is the Merit Series.
Furnaces in the Lennox Merit Series are powered by gas and typically have an fuel efficiency rating of between 80 to 93 percent. The entry-level model is known as the G40. The ML193 model features a higher
fuel efficiency rating and a design that separates the blower compartment from the rest of the machine.
Other Lennox furnace lines include the Elite series and the top-of-the-line Dave Lennox Signature furnaces.