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Furnace Buying Guide

How to compare residential furnaces by heating capacity, AFUE, staging, blower performance, venting, controls and installation requirements.

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Make the decision based on the complete system

Furnace selection starts with the home's heating load, not the input rating of the old furnace. Oversized furnaces can create short cycles, temperature swings and airflow-related limit problems.

Efficiency, staging and blower technology affect price and comfort, but the furnace still has to work with the existing or new cooling equipment and duct system.

Venting, combustion air, gas piping, condensate disposal on condensing furnaces and electrical/control requirements are part of the installation—not afterthoughts.

Buying Factors

What deserves attention

Heating output

Compare usable output capacity, not only furnace input Btu/h.

AFUE

AFUE is a standardized fuel-utilization rating; actual operating cost also depends on weather, fuel price and system operation.

Staging

Two-stage and modulating furnaces can operate at lower output during lighter loads, potentially improving comfort and cycle length.

Blower capability

The blower must support both heating airflow and any connected central cooling or heat-pump equipment.

Venting

Furnace efficiency and design determine venting and combustion-air requirements.

System compatibility

Coil cabinet size, controls, airflow and physical installation conditions should be checked before selection.

Installation Matters

The equipment label is only part of the purchase

Correct sizing, component matching, airflow, refrigerant setup, electrical work, drainage, controls and duct-system condition all affect how new equipment performs after installation.

A higher-efficiency unit installed into a poor air-distribution system can still deliver poor comfort and disappointing real-world performance.

Compare Proposals

Compare scope—not just the bottom-line price

Two proposals can use similar equipment while including very different labor, accessories, warranties, duct modifications, electrical work, permits and commissioning procedures.

Ask contractors to identify exactly what is included, excluded and assumed.

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Homeowner Tools

Check the numbers before making a decision

Use Central HVAC's homeowner tools to estimate system age, develop a preliminary replacement budget and review the scope of a contractor proposal.

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SmartQuote IQ™

Review the pricing, equipment, scope and warranty language in an HVAC proposal.

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