Heating systems are available in various models, each with a range of sizes to accommodate different-sized homes. Heating system size refers to the heating capacity measured in British thermal units (BTU). While it may not seem like a big deal, getting the proper-sized unit for your home is critical. This guide will explore why size matters and how to determine the best size for your home.
Heating Effectiveness
When installing a new heating system, one of the goals is usually to heat your home more effectively than the previous system. Whether your system is too big or too small, it won’t effectively heat your home. An undersized unit will run constantly but never reach your set temperature. An oversized unit will short cycle, never running long enough to achieve your ideal comfort.
Energy Consumption
In addition to heating more effectively, most property owners want to get an improvement in the energy they consume. Whether your system uses natural gas or electricity, a new one should be more efficient than an older one. A heating system uses the most energy when starting a heating cycle. A short cycling, oversized system will experience more starts, driving up the power it consumes. An undersized system may not short cycle, but it will still consume more energy because it runs longer cycles. In both cases, you pay more for your energy but never achieve your desired comfort.
Household Temperature Consistency
A central heating system distributes air by circulating air as the heating cycle runs. The system produces positive air pressure at the supply vents and negative air pressure at the return vents. The Pascal principle explains that pressure equalizes in a container, so the heat produced at the supple vents gets drawn throughout the house by the negative pressure return vents. An oversized system doesn’t allow the system to run long enough to move the heat evenly throughout your home. Conversely, an undersized system doesn’t produce enough pressure or heat to heat your home effectively.
Repair Frequency
Every HVAC system will eventually need some repair, but it should be near or after the manufacturer’s warranty expires, usually ten years or more after installation. Improperly sized systems experience excessive wear. Oversized systems experience wear during excessive starts as they short cycles. Undersized systems experience it because of the longer heating cycles. In either case, you’ll experience parts that wear out more quickly, from the circulating fan to the ignition for a gas furnace or the compressor for a heat pump.
Unit Service Life
With an appropriately sized unit, gas furnaces and modern heat pumps should last 15 to 20 years with proper maintenance. However, the extra wear of an improperly sized unit may drastically cut that service life. Generally, you want to consider replacing a heating system when one of two possible factors is present. First, if there is any repair that costs more than 50% of the cost of a new unit, such as a bad compressor or cracked heat exchanger. The second is when the sum of total repairs over the last two years multiplied by the age of the system exceeds the cost of a new system. When your repair frequency increases due to being too large or too small, it will significantly affect the second equation and accelerate when you experience the first.
Installation Costs
The cost of installing a new HVAC system should be considered in two ways. The first is the total cost of the installation. Installing a larger system usually means you’ll pay more for it than you would for a properly sized option.
The second consideration is the system’s annualized cost or installation cost spread over the system’s life. A heating system can seem expensive, so if you have to replace it more frequently, you’ll feel that pain sooner than you should. If you install an undersized system trying to save a little money right now, you’ll significantly increase the annualized cost.
Whether you install an oversized or undersized system, you’re likely to replace it before it reaches the end of its service life because it won’t effectively heat your home. You’ll notice that it’s constantly uncomfortable and eventually want something more effective.
Ductwork Compatibility
Your ducts work with your central air handler and heating system to draw air in to heat and deliver it back to the rooms throughout your home. However, your heater must get adequate airflow through your ducts to heat effectively. If the heater is oversized for the ducting system, it will choke for air and strain to draw more. An undersized unit for the ductwork won’t draw enough air through the ducts to produce the pressure needed to create circulation.
Operational Noise Level
Noise is one of the chief complaints about HVAC systems, especially heating systems. While they shouldn’t produce much noise when operating properly, an improperly sized system may have more noise. Larger systems will generally produce more noise. However, an oversized system may also make extra noise, like banging in the ducts from trying to force too much air through the system.
Environmental Consideration
The focus on the impact residential heating has on the environment has continued growing over the last few years. Even if you’re using an all-electric system and not burning fuel, someone has to generate that electricity. When you consume more power to run an improperly sized unit, you further contribute to the power generation problem, either burning fossil fuels or requiring more solar or wind power production. Getting the proper size heating system for your home helps reduce your direct and indirect carbon footprint and environmental impact.
Impact on Indoor Air Quality
Your heater is integral in managing your home’s indoor air quality, which helps keep your home healthy. To work effectively as part of your air quality management, the system must draw the proper amount of air through the filter. With the airflow issues created by both undersized and oversized systems, your filter won’t work as effectively as it could, leaving more contaminants in your air, resulting in more frequent illness and more allergy and asthma triggers.
Determining the Proper Size Heating System
Professionals use a process to evaluate a home and determine the size of the heating system needed. It’s called the Manual J load calculation, which evaluates how much heat the house generates. It considers the size of the house plus aspects of the home’s construction, like ceiling height, number and size of windows, insulation, and more. Further, it considers the number of occupants, the shade it receives, and major heat-generating appliances. These aspects can affect the size system you need, so it’s essential to go beyond simply measuring the home’s square feet.
People around Gilbert trust A/C & Plumbing Doctors when they need professional help maintaining their homes. Our experienced team of HVAC technicians provides AC and heating installation, maintenance, and repair. We also offer ductwork installation and repair, heat pumps, indoor air quality solutions, and a wide range of residential plumbing services. Call to schedule a consultation with one of our NATE-certified installation technicians to evaluate your home’s proper size heating unit.
