Ductless Mini-Split Heat Pump Sizing Guide

This guide provides general estimates to help you choose the right capacity. Every home is different—insulation, climate, sun exposure, and ceiling height all matter—so please treat these as planning numbers and consult a qualified professional for final sizing.

Quick Room-Size → BTU Chart

Room Size (sq ft)	Typical BTU (cooling)	Indoor Unit
100–150	6,000 BTU	6k wall mount (Multi-Zone)
150–300	9,000 BTU	9k wall mount
301–500	12,000 BTU	12k wall mount
501–750	18,000 BTU	18k wall mount
751–1,000	24,000 BTU	24k wall mount
1,001–1,500	36,000 BTU	36k wall mount

Note: For open plans or high heat load spaces, choose the higher end of each range.

Adjustments to Consider

• Climate: Hot/humid summers or very cold winters → move up one size.
• Insulation & Windows: Poor insulation, single-pane, or large west/south windows → move up one size.
• Ceilings: Add ~10% capacity for 9–10 ft ceilings; ~20% for vaulted/lofted spaces.
• Sun & Usage: Kitchens, home gyms, server/AV rooms, or all-day sun → move up one size.

Multi-Zone Planning

• Size each room’s indoor unit by its needs (use the table above for each zone).
• Choose a condenser whose total rated capacity meets (or slightly exceeds) the expected simultaneous load. Not every room peaks at once.
• Long line sets, elevation changes, or branch lengths can affect performance—follow manufacturer limits.

Heating Considerations

In cold climates, look for heat-pump systems with low-ambient heating specs. Check the model’s rated heating capacity at your typical winter temperature.

Examples

1. Bedroom 180 sq ft (quiet, shaded): 6k BTU.
2. Kitchen + dining 420 sq ft (sunny, cooking heat): 12k–18k BTU; often 18k performs better.
3. Two bedrooms, 150 sq ft each: Two 6k–9k heads on a 2-zone condenser sized for ~12k–18k combined.

Electrical & Installation Notes

• Confirm breaker, wire gauge, and dedicated circuit per the unit’s nameplate and local code.
• Observe maximum line-set lengths and elevation differences; use the correct diameter and flare torque.
• Follow all manufacturer instructions; some work may require a licensed electrician.

Start the Mini-Split Builder to match rooms and line-set options, or contact us for guidance.

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