Natural Gas-Fired Heat Pumps: Are They Right For You?
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Discover how gas heat pumps can help you achieve excellent efficiency and low running costs with your home heating and cooling needs. Check out the advantages and disadvantages of gas-fired heat pumps and how they compare to electric types.
What are dual fuel heat pumps, and how they work
Gas-fired air conditioning was widespread over fifty years ago, but it lost its popularity because of low efficiencies and the higher cost to buy and install systems. Electrically powered heat pumps became popular because they were more efficient and they consume less energy. They are also cheaper to buy, install, and run. However, in some cases, electric heat pumps are less well suited to larger homes, which often require zoned temperature control, so the latest natural gas-fired heat pumps are gaining popularity.
Home sizes are growing
Advances in natural gas cooling technology have developed natural gas-fired heat pump systems, specifically for use in larger residential properties. This is a direct result of the growth in the size of new homes. The average home is now 2000 sq. ft., with more than 10% of new homes in the 4000 sq. ft. plus range, where standard heat pumps are often not ideal.
Absorption heat pumps are air-source units powered by natural gas, propane, solar, or geothermal heated water instead of electricity, but because natural gas is the most commonly used power source, they are usually known as gas-fired heat pumps.
They work in a different way to an electric heat pump, but they don't use ozone-damaging refrigerants under high pressure. Instead, they use ammonia as a natural refrigerant with water as an absorber.
How a gas-fired absorption heat pump works
A gas-fired absorption heat pump incorporates a generator, and an absorber, which combined is called a thermal compressor. This replaces the electric compressor, which is standard in air conditioning and heat pump systems. Using a pump rather than a compressor makes greater efficiency and lower running costs achievable.
An ammonia and water solution is heated by gas in the generator to raise the pressure. This results in the ammonia separating into a vapor, leaving a weak ammonia/water solution.
This solution passes into the absorber unit, and the ammonia vapor is pumped through the condenser, where it condenses as it passes through, releasing its heat into the room.
As the heat dissipates, the ammonia becomes liquid again but remains under high pressure. It then passes into the evaporator unit via an expansion valve, which lowers the pressure as it passes through. Reducing the pressure lowers the temperature at which the ammonia will boil. It passes into the evaporator, and returns to a vapor, evaporates, and quickly becomes very cold, pulling heat from the surrounding air, which drops in temperature as the solution gets warmer.
The warmed ammonia vapor passes back into the absorber unit, where it re-recombines with the weak ammonia/water solution. It returns to a liquid and discharges any remaining heat into the system.
The re-combined ammonia solution returns to the generator unit, where the cycle starts over.
Gas heat pumpAn available addition to a natural gas-fired heat pump today is a heat exchanger system [GAX], which harvests the heat given off by the generator and absorber units when it heats the ammonia to separate it from the water. This increases the overall efficiency of the process.
Advantages of a natural gas-fired absorption heat pump
- It's ideal for larger homes (4000sq. ft. +).
- They can provide controlled, zoned heating and cooling around your home.
- They use natural ammonia as a refrigerant, not an ozone-damaging gas.
- They work with any energy source: natural gas, solar energy, geothermal hot water, or other heat sources.
- They don't give off as many damaging emissions, unlike gas or coal furnaces, and burn much cleaner.
- They provide year-round efficiency, especially in extremes of hot and cold temperatures, where electric heat pumps may struggle.
- You can still keep your home cool or warm even in the event of a power failure.
- Gas-fired heat pumps are dependable and efficient, even in freezing weather. These systems work hard to harvest heat from the area.
- Overall, gas-fired heat pumps are believed to be more efficient across the full spectrum of climates.
- The Coefficient of Performance (COP) rating measures the efficiency of air-source absorption gas-fired heat pumps. The higher the COP rating, the greater the efficiency of the equipment.
Drawbacks of a natural gas-fired heat pump
- Higher cost to buy, install and run, but the efficiency over the seasons is high, especially in climates, which can be very cold or very hot and humid.
- Gas-fired heat pumps most often use natural gas, which is more expensive than electricity.
- Carbon monoxide poisoning is a risk with any gas appliance. You should always install a dependable carbon monoxide sensing system on your property if you have any gas appliances.
Heat pumps in extreme climates
Electric systems can struggle to deliver adequate levels of heating, especially in extremely cold weather. Weather conditions, which are outside of our direct control, influence air source heat pumps. Inevitably their efficiency will vary according to the prevailing conditions. In a moderate climate, they will work efficiently and provide cooling and heating to keep your home comfortable all year.
In more extreme conditions with freezing winters and hot, humid summers, electric heat pumps may struggle to cope. The benefits of a gas-fired unit will become evident when the temperature plummets and the amount of available warmer air lessens. An electric heat pump will have to work extra hard to operate efficiently, which in turn means higher power costs and wear to your equipment as it will be running flat out to cope.
Benefits of a heat pump
- Energy-efficient, capable of delivering up to three times as much energy for each unit used.
- Electric heat pumps cost less to run because they use electricity.
- Electric heat pumps are more efficient at maintaining a clean indoor atmosphere, one which is healthier, cleaner, and free of toxins.
- No risk of flammable gases or poisonous emissions that can occur with any gas unit.
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Drawbacks of an electric heat pump
- Most of us regard electricity as clean energy; however, the production of it still has adverse effects on the atmosphere. Electricity generation is expensive, and costs are rising year on year.
- Over time, the efficiency of a gas-fired heat pump may decrease the difference in savings you can expect from an electric heat compared with a gas-fired unit.
- Heat pumps use environmentally unfriendly refrigerants, which deplete the ozone layer. Because of this fact, the most common refrigerant, R22, was being phased from use on January 1, 2020. You can see the EPA's HCFC Phase Out Schedule here.
- Afterwards, the only R22 available will be from recycled and reused materials. R22 is the most common refrigerant used in heat pumps and refrigeration for years. More modern and safer materials are now being used to help save the planet. Speak to your HVAC professional if you are concerned.
- Some electric heat pumps may not reach their full efficiency in very cold or hot, humid climates. As a result, they may struggle to achieve the range of temperatures you need to be comfortable in your home.
Conclusion
A natural gas-fired heat pump is an excellent choice, especially if you have a larger home (4000sq ft +). It will deliver greater efficiency in heating and cooling over a larger area, with the benefits of zone control.
They will also deliver greater efficiency, especially in areas where temperatures are extreme. The cost to buy, install and run is higher, but the benefit of having a system that will deliver a comfortable living environment year-round, no matter what the weather does, may offset the higher initial higher costs.
For most of us living in average homes in moderate climates, the standard electric air source heat pump should fulfill your requirements perfectly and provide you with excellent efficiency and low running costs. However, if your requirements dictate you need something more powerful, then a natural gas-fired heat pump could be your ideal choice.
In every case, you should consult a professional HVAC technician from a reputable company to discuss your specific requirements in detail and offer guidance and advice. You know it makes sense.
