HVAC Buying Guide – What to Consider When Purchasing an HVAC System

When buying a new HVAC System there are a lot of things to consider, and it can oftentimes feel daunting. Our buying guide will break things down by Basics Capacity, Efficiency Rating, Brand, Model, and Features.


The basics of comparing HVAC components and prices are first based on the capacity which is a unit of measure for heat. The measures are expressed in British Thermal Units (or BTUs) or, as an equivalent measure which you may also hear, Tons. Why Tons? Because we relate the measurement of heat to mass or weight, and this is how.

One BTU is defined as the amount of heat needed to raise the temperature of 1 pound of water by 1 degree Fahrenheit. These two measures can be easily converted – 12,000 BTUs = 1 Ton of cooling/heating capacity.

Specifications for HVAC output are expressed in BTUs per hour (BTU/h) to indicate the amount of heat applied or removed in a standard unit of time. So, if someone tells you that you have a “two and a half (2½) ton A/C unit” in your house, it means your air conditioning system’s cooling capacity is 30,000 BTUs, (or 2.5 x 12,000 BTUs), or it cools at a rate of 30,000 BTUs/hr.


When it comes to HVAC systems, efficiency is simply the ratio of capacity to the amount of power needed to operate the equipment. Efficiency is expressed in a few different ways depending upon the type of heating or cooling equipment.

For air conditioning and the cooling capacity of heat pump systems, you will commonly see the Seasonal Energy Efficiency Rating, or SEER. This is the capacity divided by the amount of energy, so the higher the number the better – a higher number means the system has a greater capacity at a lower energy level.

As an example, if there are two 3-ton (36,000 BTUs) air conditioning systems, one with 14 SEER and another with 16 SEER, the 16 SEER would be more efficient.

For heating systems, there is a rating for heat pumps and a different rating for gas furnaces. For heat pumps, there is the Heating Season Performance Factor, or HSPF, which is like the heating equivalent of SEER. The HSPF of a heat pump is defined as the output of heat in BTUs over the electricity consumed (measured in watt-hours) for the heating season. Additionally, since HSPF and SEER are measured by a season’s duration, they represent the performance at a seasonal average temperature.

For gas furnaces, the measure of efficiency is called the Annual Fuel Utilization Efficiency rating, otherwise known as AFUE. AFUE is the percentage of the fuel used in the furnace converted to the heat output of BTUs. Another way to calculate the AFUE is to take the theoretical amount of energy contained in the fuel divided by the actual energy output multiplied by 100.


When considering with HVAC unit to purchase, another important factor to consider is the brand. The best way to narrow down your options is to compare prices that use the same equipment. This can be tricky because even within one manufacturer, there can be various models with the same capacity and efficiency, but have different levels of performance.

For most brands, models are tiered as “good”, “better”, and “best”, from the lowest price to the higher price, and from basic to the most extra features/options. Fortunately, names of product lines make it easier to keep track. It is important to take time to research brands and their units to ensure that you get the best value for your money.


Especially when considering the purchase of a mid-tier or high-tier HVAC unit, it is important to research the most common advanced features, which are listed below.

Sound Rating

One feature will be how quiet the unit is. The units have a sound rating in Decibels or dB, where the lower, the number, the quieter the unit will be. This may be more of a concern with some people depending on the location of the outdoor unit, for example if it is near a bedroom or where family members gather to entertain, or watch movies, or a room used for study, or listening to music.

Blower Speed

Another feature available on some models is the variable speed of blower-fan motors. These motors are what circulates air through your home’s ducts and registers. The blower-fan speed affects the airflow and not only impacts the heating and cooling performance, but also the efficiency of the system.

Fan motors in HVAC systems that are currently on the market must comply with the U.S. Department of Energy (DOE) Fan Energy Rating (FER). The FER sets a standard for the amount of electricity (in watts) used to produce a unit of airflow, which is measured by every 1,000 cubic feet per minute (CFM).

Basic HVAC systems are equipped with fixed-speed blower motors, which turns the fan on when the cooling or heat comes on and when the temperature sensors reach the set temperature, it switches off. This means that the system either blows full-speed, or not at all. Most people do have issues with this full-run/full-stop operation related to their comfort, or their annoyance by the sound of the air pushing through the vents.

Many high-tier HVAC units have variable speed blower motors instead of fixed, which have discrete speeds that can be set by the owner. The increased efficiency of these options can result in noticeably lower electricity bills. These options also result in consistent airflow from the time the heating or cooling starts, and less abrupt temperature changes.

Variable speed motors also help to evenly distribute air and maintain a healthy amount of humidity in your home. When the fan starts, running at the slower speed, the air moves slowly through the refrigerated coils. The longer it moves through the coil the more water condenses from the air. As moisture is removed from the air fan speed increases circulating the cooler, drier air to the rooms in your home.

Two-Stage Heating and Cooling

Another advanced feature available in some models, is two-stage heating and cooling. Some air conditioning systems, heat pumps, and furnaces have two-stage operation. Some of the most elaborate and most high efficiency air conditioning and heat pump systems (up to about 20 SEER and 9 and above HSPF) operate with a variable speed compressor with a range of the capacity (for example from 40-100%)

The single stage heat pump, furnace, or air conditioning unit only operates at its full capacity for the entire time it is cycled on from the temperature setting on your thermostat. Two-stage units can operate at a lower capacity on less hot or humid days (for air conditioning/heat pump systems) or milder days during the winter (for furnaces and heat pumps), thereby operating while using less electricity.


To conclude, while there are many options to consider when choosing an HVAC unit and they can seem intimidating at first glance, it’s pretty simple. If you do your research on, and compare the basics capacity, efficiency, brand, model, and features of each unit you are considering, it will ensure that you make the right decision for both you and your wallet.

If you have any questions, please give us a call at (410) 252-7400