Gas heaters come in various sizes, including portable, wall-mounted, and central units, typically ranging from 10,000 to 200,000 BTUs to suit different spaces.
Choosing the right gas heater size is crucial for efficient heating and comfort. Gas heaters come in various sizes measured in BTUs (British Thermal Units), ranging from small portable units to large whole-house systems. This guide covers all available gas heater sizes and their ideal applications.
Understanding Gas Heater Sizes (BTU Ratings)
BTU ratings determine a gas heater’s heating capacity. Higher BTU ratings mean more heating power. The size you need depends on:
- Square footage of the space
- Ceiling height
- Insulation quality
- Climate zone
- Number of windows/doors
Small Gas Heaters (10,000-30,000 BTU)
Ideal for:
- Single rooms (100-300 sq ft)
- Bedrooms
- Home offices
- Small garages
Examples include indoor propane space heaters and compact quartz heaters.
Medium Gas Heaters (30,000-60,000 BTU)
Best for:
- Large rooms (300-700 sq ft)
- Open floor plans
- Small apartments
- Workshops
Large Gas Heaters (60,000-100,000 BTU)
Suitable for:
- Whole-house heating (1,000-2,000 sq ft)
- Large garages
- Commercial spaces
- Outdoor patios
Extra-Large Gas Heaters (100,000-200,000+ BTU)
Designed for:
- Industrial spaces
- Warehouses
- Large commercial buildings
- Pool heating (check Raypak pool heaters for examples)
Gas Heater Types by Size
Portable Gas Heaters
Typically range from 10,000-50,000 BTU. Great for temporary heating or supplemental warmth.
Wall-Mounted Gas Heaters
Usually 15,000-40,000 BTU. Space-saving solution for permanent installation.
Built-In Gas Heaters
Range from 30,000-150,000 BTU. For whole-house systems. See our guide on built-in gas heaters for options.
Pool Heaters
Specialized units from 100,000-400,000 BTU. The Lennox SL297NV is an example of a high-efficiency gas furnace.
Choosing the Right Size
Use this simple calculation:
- Measure your space (length × width × height)
- Multiply cubic feet by 0.133 for moderate climates
- Multiply by 0.18 for colder climates
- Add 10% for each exterior wall
- Add 10% for each window/door
| Room Size | BTU Needed |
|---|---|
| 100 sq ft | 5,000-10,000 |
| 200 sq ft | 10,000-18,000 |
| 300 sq ft | 18,000-25,000 |
| 400 sq ft | 25,000-35,000 |
| 500 sq ft | 35,000-45,000 |
Special Considerations
High-Ceiling Spaces
Add 25% more BTU for ceilings over 8 feet.
Poor Insulation
Increase BTU by 30-50% for drafty spaces.
Commercial Use
Consult HVAC professionals for proper sizing of large spaces.
Energy Efficiency
Higher BTU doesn’t always mean better. Oversized heaters:
- Waste energy
- Cycle on/off frequently
- Create temperature swings
- Reduce equipment lifespan
Look for ENERGY STAR certified models for maximum efficiency.
