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Full System vs. Half System for Your HVAC Equipment

Air conditioners and furnaces can be replaced on their own or together, and there are pros and cons to pairing them when upgrading your HVAC system.

Full System vs. Half System for Your HVAC Equipment

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Joshua Rodriguez


August 3rd, 2020

When it’s time to replace your air conditioner or furnace, it might also be time to replace the other.

This seems obvious when, for example, your entire HVAC system is 20 years old and both could be considerably upgraded. However, it can be less obvious when one breaks down and isn’t worth repairing, but the other is still going strong.

What do you do in those cases? Is it the best option to replace the busted half but leave the other to replace it in another 3-10 years? Or will you benefit from replacing both, even if one is still functioning relatively well?

While there isn’t a single answer that will be true for all homeowners, there are considerations that will help make your decision easier. We talk to thousands of homeowners each year, and many are only looking to replace an A/C or furnace. Of those, some do only replace the half system, and that’s the best choice for them. Others take the plunge on a full system, and it’s frequently the best decision for their long-term budget, comfort, and peace of mind.

We’re going to walk you through some considerations in this article for both. By the end, you’ll either know which option is right for you, or you’ll at least have a better sense of what information you’ll want to gather from your HVAC contractor to make the right choice.

A furnace and an air conditioner.

HVAC Equipment Matching: Limits & Possibilities

There are a lot of options in HVAC, but many of them can be broken down into a handful of categories. To talk about air conditioners, furnaces, and equipment matching, here are the broad categories of interest:

  1. Single-stage equipment
  2. Two-stage equipment
  3. Variable-speed equipment

There are several options within each of those categories, but the biggest point to remember is that the speed of your A/C has to match the speed of your furnace.

Why is this? Well, this is where it’s important to remember that your HVAC system is just that: a system. The heating and cooling equipment doesn’t exist in separate silos.

Most importantly, the blower motor in the furnace is what provides airflow for the entire system, including air conditioning. Therefore, the blower motor needs to be able to match the options in the air conditioner for the two to work well together.

So if you have an air conditioner with hundreds of speeds (variable-speed) and a blower motor that can only turn on or off (single-stage), you’re wasting the vast majority of your air conditioner’s potential.

In cases like that, it’s also possible that the equipment is simply incompatible. So not only would you not get the most out of the air conditioner, but it wouldn’t work at all.

Equipment Matching in Replacements

If you’re looking to stay at the same equipment level, maybe this won’t be an issue. But, for example, if you currently have a single-stage system and want to upgrade to a two-stage system, replacing only an A/C or furnace won’t be in the cards.

This is why it can be useful to replace them at the same time. You’ll get equipment that is designed to work together in every way, not just regarding the blower motor. This has long-term implications for your comfort and utility bills.

A scale between cost and benefit leaning towards benefit.

Budgeting Considerations

We get it. We really do. HVAC systems are a large investment. Especially if you weren’t planning on having to replace both, it can be a gut punch to realize that your entire system needs replacing.

There’s good news, though. We help hundreds of homeowners a year who are worried about their heating and cooling options, and more often than not, we find a solution that fits their budget.

And, believe it or not, going with a full system instead of a half system can be better for your budget in several ways. Don’t believe me? Read on.

Budget Item #1: Financing

Financing is generally available for any large HVAC investment, though the standards for qualifying vary based on the company and the equipment being purchased. The good news here is that financing for full systems is often superior to that offered for half system replacements. What makes them better can vary, but it often means things like 0% interest for a significantly longer time, or lower interest rates past that period.

Budget Item #2: Warranty

New equipment almost always comes with a warranty. The most standard in the HVAC industry is a 10-year warranty on parts. Some extended warranties also include labor or go out to 12 years.

The draw here for a full system isn’t that the warranty is any longer or better, but that both major pieces of equipment are under the same warranty. If the older half of your system breaks down, it could negatively affect your newer equipment, but won’t be covered under the same warranty. This could happen with a coil leak that corrodes a portion of your equipment, for example.

This also gives you peace of mind knowing that you won’t have to deal with a large HVAC investment for up to a decade or more (ideally, 15-20 years). And if you leave your home before the warranty expires, most are transferable to the new owner, so it can increase the value of your home, or at least won't decrease the value due to a system that needs to be replaced.

Budget Item #3: Labor and Maintenance

The air conditioner and furnace themselves won’t necessarily be any cheaper if you install them at the same time. However, your labor costs are almost assuredly going to be lower. The cost of labor is a major component of pricing in HVAC, so cutting those costs can save you hundreds or even thousands.

Additionally, while any system should be serviced regularly by an HVAC professional, new systems tend to need less maintenance work and small repairs, which will often save you hundreds more per year in upkeep costs

Budget Item #4: Incentives

This will be the most variable depending on where you live, but incentives for full system installations are frequently available from utility companies, manufacturers, and the HVAC installers themselves.

At various points in our history here at Fire & Ice, we’ve included thermostats and high-quality media filters for free as part of full system installations, a savings of several hundred dollars, or even thousands depending on the thermostat and labor costs involved.

Additionally, manufacturers will sometimes offer rebates for full system replacements that aren’t applicable in a half-system installation.

Budget Item #5: Rising Costs

HVAC equipment doesn’t get cheaper. It’s sad, but true. Even the most conscientious and efficient HVAC contractor is subject to the whims of production, manufacturer, and industry costs to remain financially solvent.

For you, this means that the system you’re thinking about this year will, at best, be the same cost next year. And most of the time, it will cost more.

Of course, an extra year might put your family in a better place to be able to work an HVAC system into your budget. So it can still be the right choice to wait. But if not much is going to change, the phrase “there’s no better time than now” is especially true for HVAC investments.

Budget Item #6: Efficiency & Comfort

Even if a system is functioning properly, if it’s over 10 years old, it’s sometimes a lot less efficient than modern equipment. This efficiency translates to your overall comfort, but also your monthly utility costs.

Putting a price on comfort is more of an inexact science, but many homeowners will be happy to tell you about how much better things are in their home with a brand new system.

So what happens when you combine each of these financial benefits?

While none of these alone are likely to affect your budgeting significantly, together they definitely can. If each area can be worth hundreds or even thousands, you’re often saving several thousands of dollars with a full system replacement as opposed to waiting on one or the other. This savings is both in the short-term and long-term.

Children playing on the floor with the parents watching.

Comfort Benefits of Full HVAC System Replacement

If the information above sounds a little bit like an advertisement for a full system, it’s only because we see hundreds of families each year who try to string along an old system year to year and end up paying a lot more for it in the long-term.

Sometimes this is unavoidable, but often, it’s an avoidable situation caused by a lack of knowledge of the true costs associated with HVAC equipment.

We’re going to talk about some scenarios below where it doesn’t make sense to get a full system, but first, we want to be exhaustive in letting you know why it might be the right decision for you.

It’s easy to talk numbers when it comes to financial gains, but harder to impart how much more comfortable a new system can be. The average American spends over 90% of their life indoors, and most of that is in their home. It’s worth it to maximize your comfort during those times.

Comfort can mean many things, including:

  • Quieter operation
  • Less hot and cold spots in hard-to-reach areas of the house
  • In two-story homes, less of a divide between the temperature upstairs, downstairs, and in the basement
  • Quicker time to cool or heat, particularly when there are a lot of people in the home (parties, gatherings, etc.)
  • More options for programming your thermostat, to cater your heating and cooling to those times when you’ll be home the most
  • Better humidity control, avoiding excessive dryness in the winter and mugginess in the summer

For you, it could be others as well, but it will mean at least a few of those items for every homeowner.

When Not to Get a Full System

Ok, so you know the reasons why you might want to consider a full system. But why wouldn’t you?

There are a couple of obvious reasons: one is that your air conditioner or furnace is relatively new, and only one needs to be replaced. Once your equipment hits about 10 years, it’s at least worth a conversation about a full system, but if you have a new system that’s still under warranty, there’s no reason to replace it.

The second is budget. We outlined a bunch of reasons above why it might make financial sense for you. But look, we don’t know your situation, and only you can make the best decision for your home. If a larger investment simply isn’t possible or ideal, that’s fine.

The good news is that a properly matched half system can produce many of the same benefits outlined above. While it’s true that a fully matched system, installed at the same time, will generally produce the most benefits, you’re getting a great upgrade even if it’s just an air conditioner or furnace.

There may be other reasons related to how long you plan to stay in the home or what the status is of the current equipment. Those will be particular to the home, though, so it’s harder to generalize about them.

Find Your Ideal System

So do you know whether or not you’d like a full system? You’re hopefully a lot closer to a decision, but it can be hard to decide without first seeing specific options and pricing.

An in-home estimate should never feel like you’re being sold to. Some companies will come in with the mentality that they need to upgrade you to a full system regardless of whether or not it’s the right choice for you.

The best HVAC contractors are happy if you’re happy. The conversation should be educational, but never pushy.

With that in mind, we hope you’ll agree that it’s worth having the conversation so that you’re fully educated on your HVAC options.

Below are a few resources that you might find helpful, on the pricing and benefits of different types of systems. It’s going to get you even closer to making an informed decision. And once you’re ready, if you’re in Columbus, Ohio, or the surrounding area, we’d love to have that conversation with you in-person.

Helpful Resources:

  1. Cost of an Air Conditioner Replacement
  2. Cost of a New Furnace
  3. Single-Stage vs. Two-Stage vs. Variable-Speed Equipment: Differences and Benefits


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