Diagnose your HVAC problem, price the fix, then decide.
Free tools for your AC, furnace or heat pump. Find out what is wrong with safe checks you can do yourself, see what the repair should cost, and know when replacing is the better deal.
National ranges, 2026
Diagnostic visit: $75–$200. Price a specific part →
All HVAC tools
| Tool | The question it answers | Covers |
|---|---|---|
| Troubleshooter | Why is my AC not blowing cold air? Why won’t the furnace start? | 12 problems, safe checks first |
| Replacement Cost | What will a new furnace, AC or heat pump cost me? Repair or replace? | By home size + the $5,000 rule |
| Repair Cost | Is this repair quote fair? | 27 parts priced |
| BTU Calculator | What size AC does this room need, and what will it cost to run? | ENERGY STAR method |
| Size Chart | How many BTU or tons for my square footage? | 100–3,000 ft² |
| Mini-Split | What size mini-split for each room, and which outdoor unit? | Single & multi-zone |
Where our numbers come from
Every price on this site is a national range from published 2026 cost guides, and every size comes from the ENERGY STAR method. Each tool shows its sources and the date we last checked them.
- Repair and replacement prices
- National installed ranges from the HomeGuide 2026 cost guides (parts plus labor).
- AC and mini-split sizing
- The ENERGY STAR room air conditioner sizing chart and its adjustments for sun, people and kitchens.
- Electricity rate
- The U.S. residential average from the EIA Short-Term Energy Outlook (about 18¢ per kWh in 2026).
- Refrigerant and efficiency rules
- EPA Technology Transitions (R-454B and R-32) and the DOE SEER2 minimums.
When a figure is our own calculation, for example adjusting a range for efficiency or interpolating between two published sizes, the drawing shows it as a dashed line. Solid lines are published figures.
We do not sell HVAC services and we are not a contractor. The goal is that you walk into the conversation with a technician already knowing what is reasonable.
What you can safely do yourself
Thermostat settings, air filters, breakers (reset once), clearing the outdoor unit and flushing a condensate drain line are homeowner jobs. Refrigerant, gas valves, capacitors and anything inside the furnace burner area are not: they need a licensed technician.
Smell gas? Leave the house without touching switches and call your gas utility or 911 from outside.
Frequently asked questions
How much does HVAC repair cost?
Most HVAC repairs cost $144–$451. Central AC repairs average $360 and furnace repairs $300.
Should I repair or replace my HVAC system?
Multiply the system’s age by the repair cost. If the result is over 5,000, replacing usually makes more sense. Run the check with your numbers.
Are these tools free?
Yes. No sign-up, no email, and everything runs in your browser.
Estimates for planning only. Prices vary by region, home, and contractor. Gas, refrigerant, and high-voltage work must be done by a licensed technician.