If you're replacing your old, worn-out furnace with a new one, it's natural to want to upgrade along the way. While there are plenty of options for high-efficiency and fully-featured furnaces, many people gravitate towards capacity. A furnace's capacity, measured in BTUs, determines its heating power. It might seem like more power is always better, but HVAC design is rarely this straightforward.

Instead, you will enjoy the most efficiency and comfort from a perfectly sized furnace for your specific home. Unfortunately, you won't always achieve this goal even by selecting a new furnace with the same capacity as your old one. In some cases, it may even make sense to go smaller! If this sounds surprising, check out these three reasons why downgrading your furnace might make a lot of sense. 

1. Your Original Installer Never Performed a Manual J

A "Manual J" load calculation is an HVAC technique for determining how much heating and cooling capacity is necessary to keep your home comfortable. While any installer should be able to perform this process, there's no guarantee your previous installer did so. If they instead relied on "eyeballing" your requirements, they may have overestimated the capacity of your heating system.

An oversized furnace does more than just cost you money on unnecessary equipment. If your furnace is too large, it will cycle much too quickly. As a result, your home will often quickly shift between hot and cold, leading to reduced comfort and wasted energy. Having your installer perform a complete load calculation can ensure your new furnace provides the correct capacity for your home.

2. You Made Improvements to Your Home

Even if your original installer correctly sized your previous furnace, your home may have changed in ways that can impact the heating load. Heating is highly dependent on air infiltration and exfiltration. In other words, how much cold air is entering your home, and how much warm is leaving your home? The better your home prevents air exchange with the outside environment, the lower your heating load.

Many things can improve how well your home helps to keep heat inside. New windows, new doors, or even improved attic insulation can greatly affect your heating requirements. A complete load calculation always considers these factors, ensuring that you can fully benefit from the efficiency gains of your home improvements.

3. You Added a Second Furnace

Homes with two furnaces are less common than those with two air conditioners, but it occasionally makes sense to add a second unit. For example, you may have put an addition onto your house and used a second furnace to extend your heating capacity. Whatever the case, a second furnace will drastically change your overall heating requirements.

In these situations, it will almost always be necessary to downsize your older furnace, assuming it's no longer heating your entire home. Installing a smaller furnace will help balance your two systems while keeping your home energy efficient and comfortable.

Speak to a heating installation service to learn more.