Similar to any product offered in the heating and air conditioning market, there bound to be some disadvantages of variable speed furnace even though it has been pushed hard and hyped up lately—primarily because of how highly profitable it is for manufactured. However, as a clever customer, it’s important for you to filter out the misleading, even wrong, information about this product.
Variable speed furnace is a term used to refer to furnaces that offer higher energy efficiency variable speed blower motor, a component in the HVAC system that activate fan to perform air circulation from the unit and over the ductwork in a home. Unlike its single speed counterpart, it can automatically adjust the fan speed based on input by sensor. It supports operation at various capacities according to the AC system requirement.
Cost-saving is often said to be one, if not the biggest advantage of using variable speed furnace. Is this claim true though? Theoretically, yes. In practice, no, especially on long-term. This statement is often advertised by manufactured based on a constantly operating motor, which in this case, the DC motors of the variable speed furnace indeed use less electricity compared to a regular motor. However, this rarely is the case for most people.
Moreover, fuel-wise, a highly efficient regular furnace and a highly efficient variable speed furnace will use similar amount of fuel, regardless of whether they use oil, propane, or natural gas.
A further problem with the claim is how it’s based on a ductwork in a proper size, which is a common issue in modern household. This shortcoming will be compensated by the variable speed motor, resulting in harder work and higher energy consumption.
Utilizing a different motor in an attempt to fix failing ducts is a band aid solution, similar to fixing malfunctioning wiring by adjusting the amount of provided power by the electrical company. The only genuine solution to resolve bad duct system is repairs by a professional contractor.
Most of the disadvantages of variable speed furnace come from the cost-saving claim by manufacturers, as explained above, but the biggest catch is probably the cost of first repair of this equipment. Variable speed furnace features much more complicated motor and control module that makes it more prone to error and faulty. Repairs cost of these items typically range between $750 and $1,500.
So, are variable speed furnaces worth it in the end? It depends on your available budget. The system is already not cheap to begin with. Therefore, it can be concluded that the cost is the primary drawback amongst other potential disadvantages of variable speed furnace that makes it not the absolute best option for homeowners.