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HVAC Load Calculator

Free HVAC load calculator. Estimate heating and cooling BTU requirements by home size, insulation, windows, and climate zone.

1,000+ Contractors Reviewed by Pros By EstimationPro Team
sq ft

Cooling Requirements

Cooling Load

42,400 BTU

Recommended AC

4 Ton

Heating Requirements

Heating Load

60,000 BTU

Recommended Furnace

60,000 BTU

Load Breakdown

Home Size2,000 sq ft
Volume16,000 cu ft
Occupant Heat2,400 BTU (4 people)
Cooling Multiplier1.00x
Heating Multiplier1.00x
Exact AC Tonnage3.53 tons
Cooling BTU / sq ft21.2
Heating BTU / sq ft30.0

12,800+ estimates calculated this month

Energy Efficiency Tips:
  • Seal air leaks around windows, doors, and ducts to reduce load by 10-20%
  • Add attic insulation to R-49+ for the biggest energy savings
  • Choose ENERGY STAR rated equipment (SEER2 15.2+ for AC)
  • A heat pump can handle both heating and cooling in Zones 1-5
  • This is a simplified estimate; a Manual J calculation provides precise sizing

HVAC Sizing & Cost Guide

System sizing guidelines, cost ranges, and load calculation factors for residential HVAC.

What Size HVAC System Do I Need?

HVAC systems are sized in tons (1 ton = 12,000 BTU/hr), with most homes requiring 2–5 tons of cooling capacity.

  • 1,000 sq ft home: 1.5–2 tons
  • 1,500 sq ft home: 2–2.5 tons
  • 2,000 sq ft home: 2.5–3.5 tons
  • 2,500 sq ft home: 3–4 tons
  • 3,000+ sq ft home: 4–5+ tons

Rule of thumb: 1 ton per 500–600 sq ft in hot climates, 1 ton per 600–800 sq ft in moderate climates. However, a proper Manual J load calculation is required for accurate sizing.

Key Takeaways

  • 1 ton = 12,000 BTU/hr of cooling
  • 2,000 sq ft home typically needs 2.5–3.5 tons
  • Manual J calculation required for accurate sizing

HVAC System Costs in 2026

A complete HVAC system replacement costs $5,000–$15,000 for a standard residential installation.

  • Central AC unit only: $3,500–$7,500 installed
  • Gas furnace only: $2,500–$6,000 installed
  • AC + furnace combo: $5,000–$12,000 installed
  • Heat pump (all-in-one): $5,000–$10,000 installed
  • Mini-split (ductless): $3,000–$8,000 per zone
  • New ductwork: $2,000–$6,000 additional (if needed)

High-efficiency systems (SEER 18+) cost 20–30% more upfront but save $300–$800/year on energy bills.

Key Takeaways

  • AC + furnace combo: $5,000–$12,000 installed
  • Heat pump: $5,000–$10,000 installed
  • High-efficiency (SEER 18+) saves $300–$800/year

Factors That Affect HVAC Load Calculations

Square footage alone is not enough to size an HVAC system. A proper Manual J calculation considers 8+ variables.

  • Climate zone: Hot/humid areas need 20–30% more cooling than moderate climates
  • Insulation levels: Poorly insulated homes may need 25–50% more capacity
  • Window area & orientation: South/west-facing windows add significant heat gain
  • Ceiling height: 9–10 ft ceilings increase volume 12–25% over standard 8 ft
  • Occupancy: Each person adds ~400 BTU/hr of heat
  • Duct condition: Leaky ducts lose 20–30% of conditioned air

Oversizing is worse than undersizing. An oversized system short-cycles, wasting energy and failing to dehumidify.

Key Takeaways

  • 8+ variables in a proper load calculation
  • Oversizing causes short-cycling and humidity issues
  • Leaky ducts waste 20–30% of conditioned air

How to Use This Calculator

Enter home size and ceiling height

Input the total conditioned square footage of your home and select the ceiling height. Higher ceilings require more heating and cooling capacity.

Select building characteristics

Choose your insulation quality, window type (single/double/triple pane), and sun exposure level to adjust the load calculation.

Pick your climate zone

Select from 7 climate zones ranging from Hot Humid (Zone 1) to Very Cold (Zone 7). This adjusts the heating and cooling loads for your region.

Review equipment recommendations

See the recommended AC tonnage and furnace BTU size, plus a detailed breakdown of how each factor affects your load estimate.

HVAC Load Calculation

Cooling BTU = Sq Ft x 20 BTU/sf x Ceiling Factor x Insulation x Windows x Sun x Climate + Occupant Heat
Heating BTU = Sq Ft x 30 BTU/sf x Ceiling Factor x Insulation x Windows x Climate
AC Tonnage = Cooling BTU / 12,000
Furnace Size = Heating BTU (rounded to nearest 10,000)

Where:

Base Cooling
= 20 BTU per sq ft baseline for cooling
Base Heating
= 30 BTU per sq ft baseline for heating
1 Ton
= 12,000 BTU/hr of cooling capacity
Occupant Heat
= 600 BTU per person (sensible + latent)

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Frequently Asked Questions

How many BTU do I need per square foot?
A general rule of thumb is 20 BTU per square foot for cooling and 30-60 BTU per square foot for heating, depending on climate. However, insulation, windows, ceiling height, and sun exposure can change this by 20-40%. This calculator adjusts for all these factors.
What size AC do I need for my house?
AC size is measured in tons, where 1 ton = 12,000 BTU/hr. A typical 2,000 sq ft home needs a 3 to 4 ton unit. Oversized AC units short-cycle (turn on and off frequently), which wastes energy and fails to dehumidify properly.
What is a Manual J calculation?
Manual J is the ACCA industry standard for calculating residential heating and cooling loads. It considers every detail: wall construction, window size and orientation, duct losses, infiltration rates, and local design temperatures. HVAC contractors use Manual J software for precise equipment sizing.
Should I oversize my HVAC system?
No. An oversized system wastes energy, increases humidity problems, and wears out faster due to short cycling. The ideal system runs for longer periods at a steady rate. Modern variable-speed systems can adjust output, but proper sizing is still essential.
What SEER rating should I look for?
As of 2023, the minimum federal standard is SEER2 13.4 in northern states and 14.3 in southern states. ENERGY STAR certified units are SEER2 15.2 or higher. Higher SEER ratings cost more upfront but save on energy bills over the 15-20 year lifespan of the equipment.
Is a heat pump better than a furnace?
Heat pumps are 2-3 times more efficient than furnaces for heating because they move heat rather than generate it. Modern cold-climate heat pumps work effectively down to -15 degrees F. In climate Zones 1-5, a heat pump is often the best choice for both heating and cooling.

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