Here’s the Truth About Dual Fuel Heating

Gas Furnace Burners

Considering a switch from an all-natural gas furnace or heat pump to dual fuel heat? If you are, you're probably familiar with conventional wisdom about dual fuel HVAC equipment.

The basic idea behind dual fuel is that it's a more energy efficient way to heat your home than, say… just using natural gas or just using electricity. This chart from Georgia Power attempts to portray an apples-to-apples cost comparison among natural gas, dual fuel, and heat pump (electric) heating. All in all, dual fuel seems like it offers slightly lower costs than electric heat and significantly lower costs than natural gas.

Pretty compelling, right? If the Georgia Power chart was the sum total of info out there on the efficiency of different heat sources, you'd probably be all in for dual fuel. Reality, however, is more complicated than a single chart reveals.

Nowadays, dual fuel isn't necessarily more energy efficient than its most popular alternatives for every home all of the time. In fact - and this is just our opinion, mind you - the question of "upgrading" to dual fuel heating equipment should actually have less to do with cost and more to do with comfort.

In theory, dual fuel heating makes sense

Most dual fuel systems are set up so that electricity heats your home when the outdoor temperature is greater than 40 degrees. When it dips below 40 degrees, natural gas heat kicks in.

The thinking is that it's overkill to heat your home with gas when things are "cold, but not that cold." Heat pumps operate pretty efficiently in those conditions, and using gas actually costs more.

However, when temperatures edge closer to freezing, heat pumps are expensive to operate and you're better off using gas - hence, dual fuel heat. In theory, it gives you the best of both worlds.

But things are changing.

Technology is changing the HVAC landscape

In recent years, gas prices have taken a serious nosedive. Like it or not, fracking has made it easier and more cost effective to extract natural gas from mother earth. The result for consumers is that it's cheaper to heat your home with gas than at any other time in recent memory, even when temperatures exceed 40 degrees.

So, do today's rock bottom natural gas prices spell doomsday for heat pumps? Not at all! In fact, heat pump technology has come a long way in the last decade or so. If your perception of heat pumps is that they're painfully expensive to operate in super-cold weather, you should get a load (pun intended) of what's on the market today.

In most cases, homeowners with new heat pumps don't have to worry about expensive "supplemental," "resistance," or "strip" heat laying waste to their electric bills. Heat pumps are better now. Even people in Vermont use electricity to heat their homes nowadays! Crazy, right?

Here's what all of this means for dual fuel heating:

  • If you already have natural gas lines connected to your house, it might be more cost-effective to stick with an all-gas furnace.
  • If you're replacing an old heat pump, going with a modern, energy-efficient heat pump probably makes more sense than dual fuel. That's especially true if your home isn't already connected to gas lines.

So far, things aren't looking so good for dual fuel anymore. If there the efficiency gains aren't as great as we thought, does dual fuel still serve a purpose?

Dual fuel heat can improve indoor comfort

We recommend dual fuel heat in this situation: Your home becomes exceedingly dry in the fall and winter, leaving you with uncomfortably dry skin.

The thing about gas heat is that it's really really hot. With gas, the temperature of the air coming out of your vents will almost always be higher than your body temperature. By contrast, heat produced by heat pumps sometimes feels cool. It isn't cool - it's warmer than the ambient temperature - but it feels that way because your body temperature is higher than the temperature of the air produced by the heat pump. New two-stage and variable speed heat pumps blow hotter air than older ones, but the air still won't feel as hot as air heated by natural gas.

Anyway, the result of natural gas's "really hot" heat is that it dries out the air a lot more than a heat pump's "less hot" heat. Some people don't like this side effect. If that sounds like you, dual fuel heating might make sense.

Here's a breakdown of heat source possibilities according to comfort concerns and HVAC infrastructure:

  • You suffer from dry skin and your home has gas lines: Take advantage of the gas lines you've got and go with dual fuel equipment. You'll get the benefits of gas and electric heating with fewer of the comfort downsides. However, if your dry skin has reached the level of total cracked-skin misery, consider switching to a heat pump.
  • You're not bothered by indoor dryness in winter: If your home is connected to natural gas, go with an all-gas furnace. Currently using a heat pump? Stick with that. It might be why the dryness isn't getting to you.

Comfort is subjective, so go with what makes the most sense for you! Here's the other thing we always tell our clients:

Your new heating equipment is going to be awesome!

If you're replacing an old system, you're going to be blown away by the efficiency and operational improvements in modern HVAC equipment. Natural gas, dual fuel, heat pump - everything is just a lot better than it used to be!

Whether you go with dual fuel or something else, just be sure to factor comfort into your decision. Different types of systems do produce different conditions inside your home. You're already getting new, high quality equipment, so efficiency is more or less taken care of. What matters most is how you want things to feel, and various heating sources have various comfort-related advantages and drawbacks.

So, does dual fuel heat make sense for your home? As with most things in life and in HVAC, it's up to you.