Original research by National HVAC Parts, based on analysis of 45,000+ OEM replacement part orders from January 2025 through June 2026. This data is free to cite with attribution to NationalHVACParts.com.
Key Findings
- Run capacitors account for 31% of all AC repair part orders — more than the next three failure categories combined.
- Flame sensors are the #1 winter part failure, representing 24% of heating-season orders. A $15 part causes the majority of "furnace won't stay lit" calls.
- July is the deadliest month for AC systems: capacitor orders spike 340% above the January baseline, with contactor orders up 280%.
- Goodman systems have the highest capacitor replacement rate per unit installed, while Carrier systems show the highest control board replacement rate.
- The average homeowner spends $47 on the part that fixes their system — compared to $350-$500 for a service call that replaces the same part.
Part Failure Rankings: What Breaks Most
Cooling Season (April–September)
| Rank | Part | % of Orders | Avg Cost | DIY Difficulty |
|---|---|---|---|---|
| 1 | Run Capacitor | 31% | $19 | Easy |
| 2 | Contactor | 18% | $32 | Easy |
| 3 | Condenser Fan Motor | 14% | $127 | Moderate |
| 4 | Control Board | 9% | $156 | Moderate |
| 5 | Compressor Start Components | 7% | $34 | Easy |
| 6 | Thermostat | 5% | $45 | Easy |
| 7 | Transformer | 4% | $28 | Easy |
| 8 | Expansion Valve / TXV | 3% | $89 | Pro Only |
Heating Season (October–March)
| Rank | Part | % of Orders | Avg Cost | DIY Difficulty |
|---|---|---|---|---|
| 1 | Flame Sensor | 24% | $18 | Easy |
| 2 | Hot Surface Igniter | 19% | $29 | Easy |
| 3 | Control Board (IFC) | 15% | $162 | Moderate |
| 4 | Pressure Switch | 11% | $24 | Easy |
| 5 | Draft Inducer Motor | 8% | $185 | Moderate |
| 6 | Gas Valve | 7% | $189 | Advanced |
| 7 | Limit Switch | 6% | $19 | Easy |
| 8 | Blower Motor | 5% | $142 | Moderate |
Failure Rates by Brand
Based on order volume normalized by estimated installed base in the United States:
Most Frequently Replaced Parts by Brand
| Brand | #1 Failure Part | #2 Failure Part | #3 Failure Part |
|---|---|---|---|
| Carrier | Control Board | Capacitor | Contactor |
| Goodman | Capacitor | Contactor | Flame Sensor |
| Lennox | Igniter | Pressure Switch | Control Board |
| Trane | Capacitor | Contactor | Fan Motor |
| Rheem/Ruud | Flame Sensor | Capacitor | Igniter |
| ICP/Heil/Tempstar | Capacitor | Control Board | Pressure Switch |
Note: Higher replacement rates do not necessarily indicate lower quality. Brands with larger installed bases naturally generate more replacement orders. Carrier's higher control board replacement rate correlates with its older installed base, not a design deficiency.
The Seasonal Failure Curve
HVAC part failures follow a predictable pattern tied to the first extreme-temperature days of each season:
| Month | Top Failure | Volume vs Baseline | Why |
|---|---|---|---|
| January | Flame Sensor | +180% | First extended cold snap — furnaces running continuously |
| February | Igniter | +140% | Thermal cycling fatigue from on/off cycles |
| March | Pressure Switch | +90% | Condensation in flue during temperature swings |
| April | Capacitor | +120% | First AC startup — capacitors that degraded over winter |
| May | Capacitor | +200% | Sustained cooling demand begins |
| June | Contactor | +250% | Heavy cycling in variable weather |
| July | Capacitor | +340% | Peak heat — capacitors fail under maximum load |
| August | Fan Motor | +190% | Cumulative heat exposure destroys bearings |
| September | Capacitor | +160% | End-of-season failures from summer stress |
| October | Flame Sensor | +220% | First heating demand — dirty sensors from summer dormancy |
| November | Igniter | +170% | Heating demand increases, igniters cycle more |
| December | Control Board | +130% | Continuous run stress, power surges from winter storms |
The DIY vs Pro Gap
Our data reveals a significant cost gap between homeowners who order parts and DIY versus those who pay for full-service repair:
| Repair | Part Cost (DIY) | Typical Service Call | Savings |
|---|---|---|---|
| Capacitor Replacement | $19 | $180-$350 | 85-95% |
| Contactor Replacement | $32 | $200-$400 | 84-92% |
| Flame Sensor Replacement | $18 | $150-$275 | 88-93% |
| Igniter Replacement | $29 | $200-$350 | 85-92% |
| Condenser Fan Motor | $127 | $350-$600 | 64-79% |
| Control Board | $156 | $450-$800 | 65-81% |
The average homeowner who orders the OEM part and does the repair themselves saves $283 per repair, based on our order data compared to national service call averages from HomeAdvisor and Angi.
Methodology
This index is based on 45,247 OEM replacement part orders processed by National HVAC Parts between January 2025 and June 2026. Orders are categorized by part type, equipment brand, geographic region, and date. Failure rankings reflect replacement demand, which correlates with but does not directly measure failure rates — some parts may be replaced preventively. Brand comparisons are normalized by estimated U.S. installed base using AHRI shipment data.
This data is free to use and cite with attribution: "Source: National HVAC Parts 2026 HVAC Parts Failure Index (NationalHVACParts.com)." For press inquiries or custom data requests, contact us.