What size AC do I need? Why won't my furnace start? Is a heat pump worth it?
Free HVAC calculators, sizing guides, and troubleshooting help, with the reasoning shown, not just a recommendation.
HVAC Calculators & Sizing Tools
Our calculators give a simplified load estimate from your climate, insulation, windows, and occupants, so you can avoid oversizing and ballpark the right size. A contractor's Manual J load calculation should confirm the final size before you buy.
AC BTU Calculator
Estimate cooling capacity for any room size. Factors in climate zone, insulation, windows, and heat sources.
AC Tonnage Calculator
Convert BTUs to tons and size central AC systems.
SEER2 Savings Calculator
Compare energy costs between different SEER2 ratings. Calculate ROI and payback period for upgrades.
Heat Pump Size Calculator
Size heat pumps for both heating and cooling. Includes cold climate considerations and backup heat.
Furnace Sizing Calculator
Calculate furnace BTU requirements. Factors in home size, insulation, climate zone, and heat loss.
Mini Split Sizing
Size ductless mini splits for single or multi-zone applications.
All calculators updated for 2026 efficiency standards
How much AC do you actually need?
Room size drives the BTU/hr your AC needs. These bands follow the ENERGY STAR room air conditioner sizing chart. Oversizing feels safe but causes short-cycling, the unit cools the air fast, shuts off, and never runs long enough to strip humidity, leaving a cold clammy room.
Complete HVAC System Guides & Resources
Whether you're replacing equipment, troubleshooting problems, or comparing options, our comprehensive guides provide the technical details and real-world insights you need.
Air Conditioning Systems
Heating Systems
How a heat pump moves heat
A heat pump doesn't generate heat, it moves it. The same closed refrigerant loop pulls heat from outdoor air (even cold air still has usable heat) and releases it indoors, then runs backwards in summer to move indoor heat out. That's why a heat pump can deliver 2–4 kWh of heat for every 1 kWh of electricity it consumes.
Energy Efficiency & Ratings
What efficiency actually saves
Higher SEER2 lowers annual cooling cost, but with diminishing returns. Going from the 13.4 SEER2 minimum to 16 saves more per point than going from 18 to 22. The chart uses a 3-ton AC with about 1,500 cooling hours a year at $0.18/kWh; run the SEER2 calculator to plug in your rates.
Indoor Air Quality
Quick HVAC Answers & Common Questions
Sizing Questions
Cost Questions
Efficiency Questions
Troubleshooting
Smart HVAC Technology & Controls
Optimize comfort and efficiency with smart thermostats and zoning systems for precise climate control.
Smart Thermostats
What smart thermostats actually save, and when a $30 programmable does the same job, with the payback math shown.
Zoning & Multi-Zone Systems
Whether zoning is worth the added cost for your home, how many zones make sense, and how to size a multi-zone mini split.
HVAC Resources & Tools
Troubleshooting
Cost Guides
How We Source Our Content
Figures come from primary sources such as the DOE, EIA, ENERGY STAR and the EPA, recalculated and linked on every page. No affiliate links or paid placements.
Data-Driven Content
Guides cite DOE, EIA, ENERGY STAR and EPA data, and the calculators use the same published formulas.
Industry Standards
Grounded in ASHRAE, ACCA, EPA, DOE, and ENERGY STAR guidance
Updated as Standards Change
Content is refreshed as standards, tax law, and equipment specifications change
Our Editorial Standards
Research Process
- Cite primary sources (EPA, DOE, ENERGY STAR, ASHRAE, ACCA, NEC) with direct links
- Cross-reference EPA ENERGY STAR databases
- Sizing tools use simplified load estimates; we recommend a contractor's Manual J before you buy.
- Include regional climate zone variations
Independence Commitment
- No affiliate links or referral fees
- No manufacturer sponsorships
- Transparent about limitations and assumptions
Start With Our Most Popular Calculator
Size your AC correctly and avoid a common, costly mistake: oversizing. Our calculator gives a simplified load estimate; a contractor's Manual J should confirm the final size before you buy.