Buying an HVAC system for new home construction, a remodeling project, or to upgrade or replace an existing system is a costly project. Knowing what an estimated price tag is going to be ahead of time can help save you money and ensure that you purchase a system that will adequately accommodate the square footage of your home. No more, no less.
When you hire a professional HVAC contractor, one of the tasks is to design a plan for HVAC coverage using a series of calculations based on several pieces of information about your home. This is important as a system that is too small or one that is too large can have a significant impact on monthly energy bills and system efficiency.
In a nutshell, the calculation helps figure out the right size system you need to do the job. If you buy a system that is too large, it will cost you more for the initial purchase plus your monthly bill will be higher. If the HVAC system is too small, your home won’t be cooled or heated properly.
There are several methods available to estimate the size of the HVAC equipment for your home. Each has its own specific things to look for.
Square feet alone – while this method gives an estimate on cooling requirements, it isn’t accurate for determining heat requirements. In order to get an accurate estimate, additional information is needed along with the square footage of the home. Other considerations that factor into the equation include the climate where you live, if the house is shaded or if it receives continuous direct sunlight, how much insulation is in the home, does the home have double-paned windows, and how “secure” is the home in terms of not having cracks, crevices, holes, and leaks that would allow for air or heat to escape.
Square feet plus climate – using both square footage and regional climate as factors allows an estimate of both heating and cooling needs. With heating, along with the climate, the region itself must also be considered. For example, what’s needed to maintain comfortable temperatures in Michigan during the winter for heating will be less than what’s needed in Florida and vice versa in the warmer months.
Sizing to existing system – the key to this method is if you’re purchasing for replacement purposes, the current system can serve as a gauge for the size of the equipment needed. In order for this method to work, you’ll need to know if the current system has also been sized correctly. A tip to keep in mind is if your system runs continuously regardless of outside temperatures throughout the year, consider it a properly sized system. If it runs in spurts, cutting off and on, regardless of temperature, most likely the system is too large for the home.
Manual J calculation – this method is considered as the top-of-the-line when it comes to sizing a system. It requires the ability to understand how to use tech-savvy software. This method should only be used by contractors with the knowledge and experience to use it correctly.
Before purchasing a new HVAC system, there are a few areas where you can help defray the cost with some simple check-ups as well as by making informed decisions.
One area that should be inspected before any work is started is the efficiency of the ductwork networked throughout your home. Problems happen with ductwork over the years that make the ducts less efficient due to age and deterioration. Another problem is wildlife and pests finding a way into your attic. These critters can create holes in the ducts or cause the ducts to become unattached. Dirt and debris can also be an issue not only with blocked vents but also in affecting air quality so it’s a good idea to have the ducts cleaned and serviced to ensure your new system will distribute air efficiently.
If you’re considering relocating the indoor or outdoor system to a more convenient spot, know that it is a big undertaking that will have an impact on the initial calculation of cost for a new system due to rerouting ductwork and electrical rewiring.
Upgrading the base or pad that the outside system sits on is also an option especially if the new unit needs a larger area to reside. The cost of removing and replacing the original pad must also be calculated into the initial price.
Insulation plays a big role in how efficiently a new HVAC system operates. If this is a new home or a room addition, you’ll want to have the appropriate amount of insulation installed based on the size of the area. For an older home, it may be time to have the existing insulation replaced and/or upgraded with high-quality insulation.
If you’re reverting the home from window units that use a ductless mini-split or central system, you can use the same sizing methods used to determine a new or replacement HVAC system.
Other things to consider are upgrading the circuit breaker box, service panel, breakers, and wiring. If the contractor is not licensed to do this work, you may need to factor in the cost of an electrician.
A basic formula used by some contractors and homeowners to arrive at an estimate goes like this: every 600 square feet in the home needs 1 ton of cooling. An easy calculation example would be a 1200 square foot home x 1 ton/600 square feet equals 2 tons. A 2400 square foot home would need 4 tons. If the home is new or relatively new, chances are it is well insulated and doesn’t have any points of entry for leaking. This type of home would be more in line with 1000 square feet per 1 ton.
Heat is measured by BTUs – British Thermal Units – and knowing your BTU needs is another step in calculating the cost. In order to size a home heating system, calculations are necessary to determine how many BTUs of heat are lost to the outside. To measure heat, use the formula of one ton equals 12,000 BTU. If you’re considering a 2.5-ton system, the formula would be 2.5 tons x 12,000 BTU/ton = 30,000 BTU.
BTUs are also used for cooling to measure the amount of heat removed from a room. In other words, you’ll need to know how much heat enters the home and buy a system that is capable of removing it.
As with any new appliance, if you don’t maintain it, the lifespan is drastically reduced. While the system is under warranty and as long as the warranty and service agreement cover issues, you’ll only need to add the price of a warranty/agreement program to the initial bill. As the unit ages and the warranty expires, repairs and replacements can add up. To cover yourself for future issues, consider purchasing an extended warranty from the get-go. It adds to the overall calculation for the amount you’ll spend upfront but in the long run, extended coverage can keep costs down and more money in your pocket.
For your part, doing a few simple maintenance projects can also keep the system running smoothly resulting in year-round comfort, better efficiency, and reasonable energy costs. A couple of things to keep an eye on is to ensure there is nothing blocking the vents or impeding continuous air flow. This can be as easy as keeping any shrubbery, vines, plants, and flowers away from the outside unit. Inside, keep vents unblocked with periodic dusting of the louver vents. You also don’t want to place any furniture flush with the wall blocking the vent system.
One of the first things a contractor should do is size up your home to determine how large the system needs to be to fulfill the needs of your home. With the help of many online calculators available at HVAC retailers, local city government websites, local utility companies, and other free calculators, you can check your daily operating cost by simply plugging in information about the potential unit such as tonnage size, number of BTUs, electric rate for kilowatt hours (kWh), number of hours of the day unit will be in use, estimated hours of usage for the month, SEER – Seasonal Energy Efficiency Ratio – level of the unit, and the number of systems in the home.
Doing the math and knowing and understanding the bottom line of all the bits and pieces that make up the price tag of a new HVAC system before signing a check or handing over a credit card is the smart route to take. With calculations done by a professional contractor compared against your own figures, you can compare and ask questions especially if your calculations aren’t in agreement with the contractor.
With this type of substantial investment you’ll be making for the purchase of a new HVAC system, and the possibility of unintentional miscalculations you want to make sure everything is correct. For the best and most accurate calculations, contact your local utility company and ask if they provide the service or hire an energy auditor to do the job.