Natural gas has a key advantage over other fuels like propane and heating oil: it arrives by pipe as a utility service, which means you don’t have to worry about scheduled deliveries. With other heating fuels, you must plan these deliveries carefully to avoid running out during a cold winter day.
If you’re looking for the most efficient gas furnaces, the best recommendation is to look for units with the ENERGY STAR label. The US Environmental Protection Agency created the ENERGY STAR program to help homeowners and businesses looking for the most efficient appliances and equipment.
Energy consuming devices can only get the label after passing rigorous performance tests, in federally approved laboratories that are completely independent from manufacturers and vendors.
Here we will provide an overview of the most efficient gas furnaces you can find in 2022 and 2023, but first we will discuss the metric used to describe their energy performance – the Annual Fuel Utilization Efficiency or AFUE.
What is the Annual Fuel Utilization Efficiency of Gas Furnaces?
Before purchasing any piece of equipment that uses energy, having an idea of consumption and operating costs is helpful. However, many different technologies are used for space heating and air conditioning, and we need a suitable performance metric for each type of system.
In the case of furnaces and boilers, the metric used to describe performance is the Annual Fuel Utilization Efficiency.
The AFUE is exactly what its name implies – a numerical value that tells the percentage of fuel energy that is converted into useful heat.
- In the US, natural gas has an energy content of around 1,037 BTU per cubic feet according to the Energy Information Administration.
- This means 100 cubic feet of gas will contain around 103,700 BTU of energy.
- If you burn this gas volume in a furnace with an AFUE of 92%, you get around 95,404 BTU of heating output (92% of 103,700 BTU).
- The energy content value of 1,037 BTU per cubic feet of natural gas is a US average. The exact energy content will vary depending on your location and gas provider.
Having a gas furnace with a high AFUE is especially useful now since natural gas prices have increased sharply. According to official US inflation data, the price of piped natural gas delivered as a utility service increased by 33% in the 12-month period between August 2021 and August 2022. This means the operating cost of a natural gas furnace is around 33% higher compared to last year.
The ENERGY STAR program has minimum AFUE requirements for gas furnaces, which vary depending on their type:
- At least 90% AFUE for gas-fired furnaces in the US South.
- At least 95% AFUE for gas-fired furnaces in the US North.
- At least 85% AFUE for oil-fired furnaces (regardless of location).
- Other than the minimum AFUE, an ENERGY STAR gas furnace must have a high-efficiency electronically commutated fan motor and air leakage of no more than 2%.
Their website has a list of states that are considered “US South” and “US North”, so you can tell which of the minimum AFUE requirements applies in your location. Keep in mind this distinction is only for natural gas furnaces – oil furnaces are subject to the same AFUE requirement throughout the country.
If you’re unsure about the ENERGY STAR label on a gas furnace, you can look for the brand and model on their website. If the label is counterfeit, you will not find that specific product.
Did you know? Old furnaces typically have an AFUE of less than 70%, or even less than 60% in many cases. By upgrading to a newer unit with an AFUE of 90% or above, you can cut gas consumption by more than one-third, while getting the same heating effect.
Saving Gas with a High AFUE Furnace: A Quick Example
Assume you replace a 60,000 BTU/h furnace having 60% AFUE, with a newer unit of the same capacity and 95% AFUE. Previously, this furnace would have required a natural gas input of 100,000 BTU/h to deliver its rated output (60,000 BTU/h), but now it only needs 63,158 BTU/h.
- 100,000 BTU/h x 60% = 60,000 BTU/h
- 63,158 BTU/h x 95% = 60,000 BTU/h
You’re still getting the 60,000 BTU/h of required heating output, but the energy input has been reduced by 36,842 BTU/h. Considering the average energy content of 1,037 BTU per cubic feet, the hourly gas consumption of both furnaces would be the following:
|Hourly Gas Consumption
|Consumption in 1,000 Hours
|60% AFUE Furnace
|96.43 cubic feet / hour
|95% AFUE Furnace
|60.90 cubic feet / hour
As of July 2022, the US EIA reported an average natural price of $24.61 per thousand cubic feet (MCF). Using this average value, the operating cost of the two furnaces above can be estimated for 1,000 hours of use.
- 60% AFUE gas furnace: $2,373 in 1,000 hours of use
- 95% AFUE gas furnace: $1,499 in 1,000 hours of use
In this example, the 95% AFUE gas furnace saves around $874 for every 1,000 hours of operation, compared with the older 60% AFUE furnace.
ENERGY STAR Certified Gas Furnaces
The following are some of the top ENERGY STAR certified furnaces that can help you save thousands of dollars over time thanks to their high AFUE capabilities.
|Lennox SLP99V Variable-Capacity Gas Furnace Series
|MAINLINE – Prestige ML98V
|Fujitsu – Prestige FF***LM98U
These furnaces are at the top of the ENERGY STAR product ranking as of October 2022, and they can all operate with either natural gas or propane gas. They are certified for all US climate regions, and they are also available in the Canadian market.
As of today, gas furnaces with an AFUE of at least 95% qualify for the Nonbusiness Energy Property Tax Credit. The tax credit amount for gas furnaces is $150, and all models listed above qualify thanks to their high efficiency. This tax credit is available until December 31, 2022, and it will then be reviewed and updated for the 2023-2032 period.
- Also consider that this tax credit is exclusively for furnace installations in existing homes used as principal residences, where the applicant is the owner.
- Gas furnace installations in new constructions and rental properties are not eligible.
Lennox – SLP99V Variable-Capacity Gas Furnace Series
This Lennox furnace offers 39% savings compared with an older 60 AFUE unit, which is equivalent to $3,886 over a five-year period. The SLP99V is characterized by its quiet operation, thanks to the Lennox SilentComfort Technology and its fully insulated cabinet.
The SLP99V also uses a variable-speed fan motor to boost its efficiency. The heat exchanger unit comes with a limited lifetime warranty, and all other components have a 10-year warranty.
Sure Comfort S98V Gas Furnace
The Sure Comfort S98V is an upflow gas furnace capable of modulating operation, achieving uniform heating and eliminating cold spots. The unit uses an ECM motor for greater efficiency and improved humidity control, and it has a direct spark ignition system that improves reliability and service life.
The S98V also has a patented heat exchanger design that improves airflow while reducing noise.
The S98V also has a smart water management system, which turns off the furnace when a drain is blocked. This prevents spills, protecting your home from humidity damage.
Rheem R98V Gas Furnace
The Rheem Prestige Series R98V is a modulating gas furnace designed for optimal comfort, and its ignition system is nine times more reliable compared with the industry average. The ECM fan motor reduces energy consumption and noise, while providing improved humidity control and indoor air quality.
Thanks to its modulating technology, the Rheem R98V can adjust speed based on heating demand, without requiring thermostat adjustments. The R98V also produces 20% less noise compared with a typical gas furnace, and it has a spill prevention feature to avoid water damage.
Ruud U98V Gas Furnace
The Ruud U98V is an upflow furnace, which also uses modulating technology to achieve a uniform heating effect. This improves indoor comfort, since temperatures become more consistent and cold spots are avoided.
Like many other products in the list above, the U98V uses an electronically commutated blower motor to improve humidity control, while reducing noise and energy consumption.
MAINLINE – Prestige ML98V Gas Furnace
The Mainline ML98V includes all the main features of top-efficiency gas furnaces: modulating operation for improved comfort, ECM technology for improved humidity control and noise reduction, a direct-spark ignition system for improved reliability.
The ML98V is built from aluminized steel and stainless steel, achieving superior corrosion resistance and thermal fatigue resistance.
The ML98V can operate as a multistage furnace at 40%, 65%, and 100% capacity, even when using single-stage and two-stage thermostats.
Russell S98V Gas Furnace
Russell is a brand owned by Rheem, and the Russell S98V is very similar to the Rheem R98V in terms of performance features:
- Modulating operation for consistent heating and cold spot reduction.
- 20% sound reduction with respect to the industry average
- Direct spark ignition for improve reliability and longevity
- Protects your property from water damage with its spill prevention feature.
Fujitsu – Prestige FF***LM98U Gas Furnace
The FF***LM98 is the most efficient gas furnace offered by Fujitsu, using an upflow design and a heat input ranging from 60,000 to 115,000 BTU. Similar to Lennox, Fujitsu offers a limited lifetime warranty for the heat exchanger and a 10-year warranty for all other parts.
The FF***LM98 improves comfort and indoor air quality by combining modulating technology with a variable speed motor. The unit has built-in diagnostics for simpler maintenance.
Should I Purchase a Gas Furnace or an Air-Source Heat Pump?
A natural gas furnace with a high AFUE (>95%) and an air-source heat pump with a high HSPF (13-14) are among the most efficient heating systems you can have at home. Like in any design decision, each option has pros and cons.
The most important difference between a gas furnace and a heat pump is the energy input, and this is key for your purchase decisions. Both options are highly efficient, but you also need to consider local energy prices.
A gas furnace may achieve a lower operating cost if you live in a city with low gas prices, but the air-source heat pump may be better in places with cheap electricity or mild winter temperatures.
Did you know? If you’re looking for a 100% renewable heating option, you can combine an air-source heat pump with a solar panel system. – This combination can also qualify for generous tax credits thanks to the Inflation Reduction Act: a 30% tax credit for solar panels and up to $2,000 for heat pumps.
Although natural gas is less polluting than other fossil fuels, emissions are unavoidable when using a natural gas furnace. The environmental footprint can be reduced drastically with a high-AFUE model, but emissions are not fully eliminated.
High-efficiency furnaces also qualify for a tax credit, but much smaller than the incentives available for solar panels and heat pumps.