Why You Need a New AC Unit (Your Complete 2025 Buying Guide)
If you’re looking to buy new ac unit, here’s what you need to know:
- Assess your needs: Determine if you need a central AC system, ductless mini-split, window unit, or portable system based on your home’s size and layout
- Size properly: Calculate the correct BTU capacity based on square footage (typically 20,000-24,000 BTU for a 1,000-1,200 sq ft home)
- Check efficiency: Look for SEER2 ratings of 15+ for optimal energy savings
- Find a professional: Choose a licensed HVAC contractor for proper installation
- Consider timing: Schedule installation during spring or fall for potential cost savings
When summer temperatures climb, nothing is more important than keeping your home comfortable. Buy new ac unit decisions can feel overwhelming with so many options, technologies, and considerations to steer. Whether you’re replacing an aging system that’s on its last legs or installing air conditioning for the first time, this guide will help you understand what matters most.
A new air conditioning system is more than just a comfort upgrade – it’s an investment in your home’s value, your family’s health through improved air quality, and significant energy savings over time. Today’s AC units are dramatically more efficient than models from even 10 years ago, with the potential to reduce your cooling costs by up to 30%.
I’m Dan W, with experience in managing home repair services and helping homeowners buy new ac unit systems that perfectly match their needs and budget. I’ve guided countless families through the selection process to ensure they receive maximum satisfaction with their new cooling systems.
Why This Guide Matters
St. Louis summers can be brutal. When temperatures soar into the 90s and humidity makes it feel like you’re walking through soup, a reliable air conditioning system becomes essential, not just a luxury. At AAA Home Services, we’ve been helping homeowners throughout St. Charles, St. Louis, and surrounding areas stay cool for over 50 years.
This guide will help you steer the sometimes confusing process of buying a new AC unit. Our goal is to help you make an informed decision that will result in:
- Cooler, more comfortable summers for years to come
- Lower monthly energy bills (a properly sized, efficient system can save you hundreds each year)
- Healthier indoor air quality for your family
- Increased home value and appeal to future buyers
Types of Residential Air Conditioning Systems
Before you buy new ac unit, it’s important to understand the different types available and which might be best for your specific situation.
Central Air Conditioning Basics
Central air conditioning systems are the most common type found in homes throughout the St. Louis area. These systems use a split design with an outdoor condenser unit and an indoor air handler or evaporator coil (typically installed with your furnace).
Pros:
- Cools your entire home through existing ductwork
- Hidden components maintain your home’s aesthetics
- Filters air throughout your entire home, improving indoor air quality
- Quiet operation (the noisiest components are outside)
Cons:
- Requires existing ductwork or the expense of installing it
- Less energy efficient if you only need to cool certain rooms
- Higher initial installation cost than room-specific options
Central AC is ideal for most homes in our service area because it provides whole-home comfort. If your home already has ductwork for heating, adding central air is usually the most cost-effective and comfortable solution.
Ductless Mini-Splits: Room-by-Room Control
Ductless mini-split systems are gaining popularity, especially in homes without existing ductwork or for additions where extending ducts would be difficult or expensive.
Pros:
- No ductwork required – installation requires only a small hole through the wall
- Zone control allows you to cool only the rooms you’re using
- Highly energy efficient – can save 30-50% compared to central systems
- Quick installation (typically 1-2 days)
- Quiet operation
Cons:
- Higher upfront cost per square foot of cooling compared to central AC
- Visible indoor units (though modern designs are sleek)
- Multiple indoor units needed for whole-home cooling
Mini-splits are excellent for older homes in areas like Webster Groves or Kirkwood where adding ductwork would be invasive, or for additions like finished basements or sunrooms. They’re also perfect for creating temperature zones in larger homes.
Learn more about how ductless mini-split AC systems can keep you cool and save you money
Window & Portable Units for Small Spaces
For smaller spaces or temporary cooling needs, window units and portable air conditioners offer affordable solutions.
Pros:
- Low upfront cost
- No permanent installation required
- Can be moved as needed
- Good for apartments or rental properties
Cons:
- Cool only a limited area
- Less energy efficient than central or mini-split systems
- Can be noisy
- Window units block light and views
- Portable units take up floor space
While we don’t typically recommend these as permanent solutions for homeowners, they can be useful in certain situations. If you’re planning to buy new ac unit for a temporary need or a small space, these might be appropriate options.
Packaged & High-Velocity Options
For homes with limited space or special requirements, there are additional options worth considering:
Packaged Systems:
- All components in a single outdoor unit
- Ideal when indoor space is limited
- Can be installed on roofs or ground level
High-Velocity Systems:
- Use small, flexible 2-inch ducts
- Perfect for older homes or historic properties
- Take up 75% less space than traditional ductwork
- Can be retrofitted with minimal disruption to walls and ceilings
These specialized systems solve specific challenges. For example, we’ve installed high-velocity systems in historic homes in Clayton and Brentwood where preserving architectural details was essential.
Sizing Your New AC: BTUs, Tons & Load Calculations
One of the most critical factors when you buy new ac unit is getting the right size. Think of it like Goldilocks – an undersized unit will struggle endlessly on hot days without ever making you comfortable, while an oversized unit will blast cold air, shut off quickly, then repeat the cycle too frequently. This wastes energy and leaves your home feeling clammy because it doesn’t run long enough to properly dehumidify.
Quick BTU Cheat Sheet
Air conditioner capacity is measured in BTUs (British Thermal Units) or tons (1 ton equals 12,000 BTUs). While these aren’t perfect, here’s a helpful starting point:
- 100-400 sq ft: 9,000 BTU (¾ ton)
- 400-700 sq ft: 12,000 BTU (1 ton)
- 700-1,000 sq ft: 18,000 BTU (1.5 tons)
- 1,000-1,200 sq ft: 21,000 BTU (1.75 tons)
- 1,200-1,500 sq ft: 24,000 BTU (2 tons)
- 1,500-2,000 sq ft: 30,000 BTU (2.5 tons)
- 2,000-2,500 sq ft: 34,000 BTU (3 tons)
Though, these numbers are just a rough guide. Your actual needs might be quite different based on your specific home.
Manual J Load Calculations vs Rules of Thumb
I can’t tell you how many times we’ve seen homes with improperly sized systems because someone used the “rule of thumb” approach. At AAA Home Services, we never guess – we use Manual J load calculations to precisely determine your cooling needs.
A proper Manual J calculation is like a cooling blueprint for your specific home. We consider everything that affects temperature: your home’s square footage, ceiling heights, insulation levels, window placement, St. Louis climate conditions, number of people living there, heat-generating appliances, and even which direction your home faces for sun exposure.
This precision matters tremendously because an oversized unit is actually worse than an undersized one. It’ll cool your home quickly but shut off before removing humidity, leaving you cold yet clammy. It’ll also cycle on and off frequently, wasting electricity and wearing out parts faster. Meanwhile, an undersized system will run constantly on hot days, never quite making you comfortable while driving up your energy bills.
When you’re ready to buy new ac unit, make sure your contractor performs this calculation. It’s the difference between comfort and compromise.
Signs You Need to Buy New AC Unit (Capacity Red Flags)
Your current system might be telling you it’s incorrectly sized. Watch for these warning signals:
Temperature inconsistency is a major red flag – if your living room feels like Antarctica while your bedroom remains stuffy and warm, your system likely isn’t properly sized or balanced. Short cycling (turning on and off frequently) suggests an oversized unit, while a system that runs constantly without ever reaching your set temperature is probably undersized.
High indoor humidity despite running your AC suggests the system isn’t running long enough cycles to remove moisture from the air – another sign of oversizing. And if your energy bills keep climbing despite similar usage patterns, your system is working inefficiently.
When we replace an existing system at AAA Home Services, we never assume the previous unit was correctly sized – even if it seemed to work fine. St. Louis homes have changed over the years with additions, improved insulation, and new windows. That’s why we always perform a fresh load calculation to ensure your new system matches your current needs exactly.
Proper sizing isn’t just about comfort – it’s about protecting your investment and ensuring years of efficient operation. When you’re ready to buy new ac unit, trust the experts who take the time to get the calculations right.
Energy Efficiency, SEER2 Ratings & Smart Features
Today’s air conditioners are dramatically more efficient than models from even a decade ago. Understanding efficiency ratings helps you make an informed decision when you buy new ac unit.
Understanding SEER2 & Why It Matters
SEER2 (Seasonal Energy Efficiency Ratio 2) is the new standard that replaced the older SEER rating in 2023. Think of SEER2 like the MPG (miles per gallon) for your air conditioner – the higher the number, the less energy your system uses to keep you cool.
When you’re looking at the numbers, here’s what matters: minimum legal SEER2 ratings are now 13.4 for the North (including our St. Louis region) and 14.3 for the South. But if you want real efficiency, look for ENERGY STAR® qualified units starting at SEER2 15.2, with premium models reaching impressive ratings of 21+.
The financial impact is significant. Upgrading from an older SEER 9 unit (common in many St. Louis homes built before 2006) to even a basic SEER2 13 system can reduce your cooling costs by about 28% – that’s potentially $300 saved every year. For most homeowners in our area, systems with SEER2 ratings between 15-17 hit the sweet spot of upfront investment versus long-term savings.
Yes, you’ll pay more initially for higher efficiency, but your monthly energy bills will thank you for years to come. It’s like investing in a more fuel-efficient car – the savings add up with every mile (or in this case, every hot summer day).
Learn more about understanding SEER ratings
High-Efficiency Upgrades Worth Considering
When you buy new ac unit, the SEER2 rating is just the beginning of the efficiency story. Several advanced features can dramatically improve both your comfort and energy savings.
Variable-speed compressors are the gold standard in cooling technology. Unlike basic systems that blast at full power then shut off completely (think of driving by constantly flooring the gas pedal, then coasting), variable-speed units can run at precisely the level needed. They operate longer at lower speeds, which actually improves comfort by removing more humidity from your home. These sophisticated systems maintain temperature within half a degree of your setting, run whisper-quiet, and can be up to 40% more efficient than basic models.
For a middle-ground option, two-stage compressors offer an excellent balance of performance and price. They operate at two levels: high for those scorching St. Louis summer days when you need maximum cooling, and low for milder days when just a little cooling will do. They’re more efficient than single-stage systems but generally less expensive than fully variable options.
Modern AC units also feature improved coil designs with improved heat transfer properties and corrosion-resistant materials. These engineering advancements might not be flashy selling points, but they significantly improve efficiency and extend the life of your system – particularly important in our humid Midwest climate.
Smart Controls & Indoor Air Quality Add-Ons
The most efficient air conditioner in the world won’t save you money if it’s not controlled properly. That’s where smart technology comes in. Wi-Fi enabled thermostats allow you to adjust your home’s temperature from anywhere using your smartphone – perfect for when plans change or you want to cool your home before returning from vacation.
The best smart thermostats go beyond remote control. They learn your schedule, suggest energy-optimizing adjustments, and provide detailed usage reports. Some can even detect when you’ve left windows open or when maintenance is needed. These intelligent controls typically add 10-15% in energy savings beyond what your high-efficiency AC unit already provides.
But comfort isn’t just about temperature. Modern AC systems can be equipped with advanced air quality features that make your home healthier. Air purification options include hospital-grade filtration systems that capture microscopic allergens, UV light purification that neutralizes bacteria and viruses, and humidity control features that maintain optimal moisture levels.
Some homeowners don’t realize that proper humidity control (typically between 40-60%) not only makes your home feel more comfortable but also improves energy efficiency. When humidity is properly managed, you can set your thermostat a few degrees higher while maintaining the same comfort level – and each degree represents roughly 3-5% in energy savings.
At AAA Home Services, we believe in finding the perfect balance of efficiency features for your specific home and budget. Whether you’re primarily concerned with lowering energy bills, improving comfort, or enhancing indoor air quality, we can help you steer the options when you buy new ac unit. And don’t forget to check if you qualify for federal tax credits for energy-efficient home improvements, which can help offset the cost of higher-efficiency systems.
How to Buy New AC Unit: Step-by-Step Process
Now that you understand the options, let’s walk through the process of purchasing and installing your new air conditioning system.
Decide: Repair or Replace Before You Buy New AC Unit
The first big question is whether you should repair your existing system or take the plunge on a replacement. This isn’t always a clear-cut decision, but there are some telltale signs that it’s time to buy new ac unit rather than sink more money into repairs.
Your AC is likely ready for retirement if it’s over 10-15 years old. Most systems have a lifespan of 15-20 years, and those final few years often come with declining efficiency and increasing repair costs. Speaking of repairs, if you’re facing a fix that would cost more than half the price of a new system, replacement usually makes more financial sense.
Another important factor is your refrigerant type. If your system still uses R-22 (often called Freon), you’re dealing with a phased-out refrigerant that becomes more expensive and harder to find each year. Frequent repairs are another red flag – if you’ve needed two or more significant repairs in the past year, your system is telling you something.
Rising energy bills despite regular maintenance and rooms that never seem to reach comfortable temperatures are the final warning signs. Our technicians can provide an honest assessment of your current system’s condition and help you make this important decision.
Ducted vs Ductless Decision Tree
Once you’ve decided to buy new ac unit, you’ll need to choose between ducted and ductless options. This decision largely depends on your home’s existing infrastructure and your specific cooling needs.
Central air conditioning makes the most sense if your home already has ductwork in good condition. It provides whole-home cooling with a single system and keeps all components hidden away except for vents and the outdoor unit. Many homeowners prefer this aesthetic, though it does come with a higher upfront cost if your ductwork needs significant repairs.
Ductless mini-splits shine in homes without existing ductwork. They’re perfect if you want independent temperature control in different zones, or if you’re adding cooling to a new addition or converted space like a garage apartment. Mini-splits also offer superior energy efficiency and quicker, less invasive installation. Many of our St. Louis customers are surprised by how sleek and unobtrusive modern mini-split indoor units can be.
Some homes actually benefit from a hybrid approach – using central AC for main living areas while adding mini-splits to solve specific problem areas like a sunroom that’s always too hot or a basement that stays too cold.
Finding a Trusted Installer & Checking Warranties
When you buy new ac unit, the quality of installation is just as critical as the equipment itself. Even the best air conditioner will underperform if improperly installed. Here’s what matters when selecting your HVAC partner:
Look for contractors who are fully licensed, insured, and bonded. NATE certification (North American Technician Excellence) is the gold standard for technicians, ensuring they have proven their knowledge through rigorous testing. Experience matters too – you want professionals who have successfully completed installations like yours many times before.
A reputable contractor will always perform Manual J load calculations and be willing to show you the results, not just give you a quick estimate based on square footage. And of course, check their reputation through reviews and references. We’re proud of our 50+ years of experience and over 8,000 Google reviews from satisfied customers throughout the St. Louis area.
Warranty coverage is another crucial consideration. Most manufacturers offer 5-10 year parts warranties, while labor warranties vary by contractor. At AAA Home Services, we stand behind our work with comprehensive labor warranties. Extended warranty options might be available for additional peace of mind.
Proper registration is essential – many manufacturers require you to register your equipment within 60-90 days of installation to activate the full warranty term. Regular professional maintenance is typically required to keep your warranty valid, which is another good reason to establish a relationship with a trusted service provider.
Learn more about our new air conditioner installation services
Rebates, Financing & Registration Must-Dos
When you buy new ac unit, there are several ways to make your purchase more affordable. Don’t miss out on available incentives that can significantly reduce your total investment.
Federal tax credits can cover up to 30% of the cost for qualifying high-efficiency systems – a substantial savings that makes premium equipment much more accessible. Manufacturer rebates change seasonally but can offer hundreds in additional savings. Just note that while utility incentives are common in many areas, Ameren electric rebates are not available in 2025 for HVAC equipment.
Many homeowners choose to finance their new system. We offer competitive financing plans that can help make your new system fit your budget. When comparing financing options, look beyond just the monthly payment to understand the total cost over the term of the financing.
After your installation, there are a few important steps to complete. Register your equipment with the manufacturer promptly – this is often required to activate your full warranty coverage. Schedule regular maintenance to keep your system running efficiently and maintain warranty protection. And keep all your documentation, including warranty information and maintenance records, in a safe place for future reference.
Register your system with the manufacturer
At AAA Home Services, we guide you through every step of this process, from selecting the right system to maximizing available incentives and ensuring your new AC is properly registered and maintained. Our goal is to make buying a new AC unit as smooth and stress-free as possible while ensuring you get the most value from your investment.
Frequently Asked Questions About Buying a New AC Unit
What refrigerant will my new system use?
When you buy new ac unit today, you’ll be getting one with much more environmentally friendly refrigerant than systems from just a few years ago.
Most modern systems currently use R-410A, which was a big improvement over the ozone-depleting R-22 found in older units. However, even R-410A is now being phased down due to its global warming potential.
The newest systems are starting to use A2L refrigerants like R-454B (sometimes called Puron Advance), which have a dramatically lower impact on the environment. These newer refrigerants essentially future-proof your system against upcoming regulatory changes that will continue to phase out higher-impact options.
This might seem like a small detail, but it’s actually important for both environmental reasons and your wallet – systems using outdated refrigerants become increasingly expensive to service as those refrigerants become scarcer.
How long does installation typically take?
“How long will I be without air conditioning?” is one of the most common questions we hear from homeowners ready to buy new ac unit systems.
The good news is that most installations happen quite quickly:
For a straightforward replacement of your existing central AC system, we can typically complete the job in a single day. Our team arrives in the morning and often has you cooling comfortably by dinner time.
If you’re installing a ductless mini-split system, installation usually takes 4-6 hours for a single zone, with additional zones adding more time. Most multi-zone installations can still be completed within 1-2 days.
For homes needing new or modified ductwork along with your AC installation, the timeline stretches to 3-5 days depending on the complexity of your home’s layout.
At AAA Home Services, we understand that being without cooling in a St. Louis summer is no fun. That’s why we work efficiently to minimize disruption, and can often offer same-day or next-day service depending on our schedule and availability.
What maintenance keeps my warranty valid?
Your new air conditioning system is a significant investment, and keeping its warranty valid should be a priority. Manufacturers have specific requirements to maintain warranty coverage, and skipping these can leave you paying out-of-pocket for repairs that would otherwise be covered.
The simplest and most important maintenance task is changing or cleaning your air filters every 1-3 months. This is the one DIY task we recommend for homeowners – clean filters keep your system running efficiently and prevent dust buildup that can damage components.
Beyond filter changes, professional annual maintenance is typically required to maintain your warranty. These tune-ups allow technicians to catch small issues before they become expensive problems, clean critical components, and document that you’re properly caring for your system.
Be sure to keep records of all service visits in a folder with your warranty information. If you ever need to make a warranty claim, having this documentation readily available makes the process much smoother.
Addressing minor issues promptly is also crucial. That strange noise or slight performance change could indicate a developing problem that, if ignored, might lead to a major component failure.
Regular maintenance doesn’t just protect your warranty – it also extends your system’s lifespan, maintains energy efficiency, and helps prevent those inconvenient breakdowns that always seem to happen on the hottest day of summer.
Learn more about air conditioning maintenance tips
Conclusion
When you buy new ac unit, you’re not just purchasing a cooling system—you’re making a thoughtful investment in your family’s comfort and your home’s value. Today’s air conditioning technology has evolved dramatically, offering smart features and efficiency levels that homeowners couldn’t even imagine a decade ago.
The journey to selecting the perfect AC system doesn’t have to be overwhelming. Working with experienced professionals who take the time to understand your specific needs makes all the difference. At AAA Home Services, we’ve spent over 50 years helping families throughout St. Charles, St. Louis, and surrounding communities create more comfortable homes.
Our approach ensures your complete satisfaction with your new cooling system. We start by conducting thorough load calculations to determine the exact size your home requires—no guesswork involved. Then we present options at different price points and efficiency levels, helping you balance upfront costs with long-term savings. Our skilled technicians handle every aspect of installation with minimal disruption to your daily life, and we provide ongoing maintenance services to protect your investment for years to come.
Don’t wait until your current system fails during the sweltering St. Louis summer heat. If you’re noticing higher energy bills, uneven cooling, or hearing strange noises from your existing unit, it’s smart to be proactive. With our fair, honest pricing and highly-rated service, we’ll help you steer the process of buying a new AC unit with confidence and peace of mind.
Your new air conditioning system will do more than just keep you cool—it will improve your home’s air quality, potentially increase your property value, and provide reliable comfort for many summers to come. The right system, properly installed, becomes an essential part of creating a truly comfortable home environment.
