How to Choose the Best Heater for Your Facility

KEY TAKEAWAYS:

  • The right heater depends on the space and how it is used, ceiling height, available fuel, zoning needs, budget, and how many hours the heater will run.
  • For standard-height rooms, a common estimate is 8.2 watts (W) of heat per square foot, or about 28 British thermal units per hour (Btu/h). That estimate assumes a 7-foot ceiling and average insulation.
  • Buildings with high ceilings, poor insulation, or frequent door openings need a professional heat load calculation instead of a per-square-foot estimate.
  • Natural gas supplied nearly three-quarters of the energy used for space heating in U.S. commercial buildings in 2018. Electric heat needs no venting or fuel supply, which makes it practical where gas is unavailable.
  • Most facilities combine heater types, such as a primary system for general heat and supplemental heaters for docks, workstations, and other problem areas.

Why Does Heater Selection Matter?

Space heating was the largest energy end use in U.S. commercial buildings in 2018, accounting for nearly one-third of their energy consumption. Heater choice affects operating cost for as long as the equipment runs.

It also affects safety and inventory. When a facility does not stay warm enough, employees may bring in their own space heaters. Unapproved heaters left unattended, placed near flammable materials, or set in walkways create fire and tripping hazards. Some products degrade or fail if after-hours temperatures drop below their storage limits.

For an overview of heater types and how each works, see [Internal link: Commercial & Industrial Heating: Complete Guide for Facilities].

What Should You Consider When Choosing a Heater?

Work through these six factors before comparing products.

  • Space and use. Identify which areas people occupy, which hold temperature-sensitive products, and which need little or no heat. Occupied areas and sensitive inventory get priority. Before deciding a space can go unheated, check what runs through it. Water lines, drains, and wet-pipe fire sprinkler piping in walls, ceilings, and unoccupied rooms can freeze and burst, even in areas no one uses. These spaces need enough heat to stay above freezing.
  • Ceiling height and volume. Warm air rises and collects beneath the roof. In tall buildings, heaters that warm the air lose more heat to the ceiling than heaters that warm people and surfaces directly.
  • Fuel availability. Check whether the building has a natural gas line, propane storage, or enough electrical capacity. Fuel availability often narrows the choice before any other factor.
  • Zoning. Decide whether the whole building needs uniform heat or only specific zones, such as a packing line, a dock, or an office.
  • Budget and run hours. Compare purchase and installation costs with operating costs. A heater that runs all winter is judged mainly by operating cost. A heater used a few hours a week is judged mainly by purchase cost.
  • Installation. Floor-, wall-, and ceiling-mounted models suit different spaces. Wall- and ceiling-mounted units free up floor space. Fuel-fired heaters also require venting or ventilation.

What Should You Consider When Choosing a Heater?

Standard-Height Rooms

For rooms with ceilings around 7 feet, estimate heater output with this calculation:

Length (ft) × width (ft) × 8.2 = watts required

To convert watts to Btu/h, multiply by 3.412. That figure comes from the standard conversion of 1 kilowatt-hour to 3,412 Btu.

The 8.2 W per sq ft (about 88 W per m²) figure is Global Industrial's sizing estimate. It is based on standard insulation and an average mid-North American climate, and it assumes:

  • A ceiling height of 7 feet.
  • Windows and doors totaling 15% of exterior wall area.
  • 3/4 air change per hour. "Air change” describes how leaky the room is. One air change per hour (ACH) means a volume of outdoor air equal to the room's entire air volume enters each hour, through gaps around doors and windows, wall leaks, and any ventilation, while the same amount of indoor air leaves. At 3/4 ACH, 75% of the room's air volume is replaced every hour.

Treat the result as a starting point. Poorly insulated buildings, colder climates, and spaces with more windows or door openings need more heat than this estimate shows.

Estimated Heater Output for Standard-Height Rooms (8.2 W per sq ft)

Area to be heated Watts Btu/h
150 sq ft (13.9 m²) 1,230 4,200
250 sq ft (23.2 m²) 2,050 7,000
350 sq ft (32.5 m²) 2,870 9,790
500 sq ft (46.5 m²) 4,100 13,990
750 sq ft (69.7 m²) 6,150 20,980
1,000 sq ft (92.9 m²) 8,200 27,980
1,500 sq ft (139.4 m²) 12,300 41,970

Btu/h values are rounded to the nearest 10.

High-Ceiling and Large Spaces

The per-square-foot estimate does not apply to warehouses, manufacturing floors, or other buildings with ceilings well above 8 feet. Heat loss in these buildings depends on more than floor area, and scaling the estimate by ceiling height overstates or understates the load depending on the building.

For these spaces, a qualified heating, ventilation, and air conditioning (HVAC) professional should perform a heat load calculation. The calculation accounts for:

  • Building volume and ceiling height
  • Wall, roof, and floor insulation
  • Window and door area
  • Air leakage and ventilation requirements
  • The local outdoor design temperature (the cold-weather temperature the system must handle)
  • How often dock and overhead doors open

For strategies specific to large buildings, including destratification fans that return warm air from the ceiling to the floor, see [Internal link: How to Heat a Warehouse or Large Commercial Space].

Should You Choose Gas or Electric?

Choose gas where the building has a natural gas line or propane supply and needs high output for large areas. Natural gas supplied nearly three-quarters of space heating energy in U.S. commercial buildings in 2018. Gas heaters require venting or ventilation for combustion products.

Choose electric where gas is unavailable, where venting is impractical, or where the heat is supplemental or limited to small areas. Electric heaters produce no combustion byproducts but are limited by the building's electrical capacity, and high-output units may require dedicated circuits or higher-voltage service.

Operating cost depends on local energy prices and how many hours the heater runs. For a cost comparison per unit of delivered heat.

Which Type of Heater Fits Your Space?

Forced-air and unit heaters. A fan blows air across a heat exchanger or heating element and distributes warm air through the space. Unit heaters are self-contained, fan-forced heaters, usually hung from the ceiling or mounted on a wall. They are a common choice for general heat in warehouses, workshops, and garages. They come in gas, electric, and hydronic models. Hydronic models have no burner or heating element of their own. They heat air with hot water piped from a central boiler through a coil inside the unit.

Convection heaters. Convection heaters warm the air and rely on natural circulation, without a fan, to spread the heat. They suit enclosed rooms with few door openings.

Infrared and radiant heaters. Infrared (IR) heaters warm people, floors, and objects directly instead of the air. They suit high-ceiling buildings, spot and zone heating, and areas with frequent door openings. Racking and equipment in the heater's path block the heat.

Hydronic heaters. Hydronic systems circulate hot water or steam from a boiler to unit heaters, baseboards, or radiant floors. They fit buildings that already have a boiler or that need heat distributed to many separate rooms.

Oil-fired heaters. Oil-fired heaters suit sites without natural gas service. They require on-site fuel storage, venting, and regular burner maintenance.

Patio heaters. Gas and electric patio heaters warm outdoor break areas, entrances, and other open-air spaces.

Specialty heaters. Some applications need purpose-built equipment. These include blanket heaters for drums, barrels, and containers; heaters rated for hazardous locations; heaters that prevent freezing in pump houses; and washdown unit heaters for dirty or wet environments.

How Should You Heat Different Areas of a Facility?

Most facilities need more than one heater type. Match each area to the heat that suits it.

Heater Types by Facility Area

Area Common choices Why
High-bay warehouse or distribution floor Overhead infrared (gas tube or electric), gas unit heaters IR heats people and floors instead of air that rises to the ceiling
Loading dock IR heaters, unit heaters Radiant heat holds up better when doors open
Manufacturing floor Gas infrared tube heaters, unit heaters Broad coverage for large production areas
Workshop or maintenance bay Unit heaters, IR heaters Fast heat for open work areas
Office or break room Electric wall, baseboard, or convection heaters; hydronic baseboards Quiet heat for enclosed rooms
Packing station or single workstation Electric or gas infrared (spot heat) Warms one area without heating the whole building
Outdoor break area or entrance Patio heaters, outdoor-rated IR Radiant heat stays effective in moving air

For door seals, air curtains, and other ways to reduce heat loss at docks.

Should the Heater Be Primary or Supplemental?

A primary heater provides consistent heat across a whole building or zone. Choose a system sized to the full heat load, such as unit heaters, overhead infrared, or hydronic heat.

A supplemental heater targets a specific area where the primary system falls short, such as a drafty entrance or an isolated workstation. Choose a heater that delivers heat where it is needed, such as a spot IR or wall-mounted electric heater.

Do You Need Portable Heat?

Portable heaters cover temporary and seasonal needs, such as a construction or renovation area, an equipment outage, an outdoor work area, or drying out a space after a leak. For portable heater types and portable heater safety.

Frequently Asked Questions

How many watts do I need to heat a room?

For a room with a ceiling of about 7 feet, multiply the floor area in square feet by 8.2 to estimate watts. A 1,000 sq ft room needs about 8,200 W. Poor insulation, a cold climate, or a higher ceiling increases the requirement.

How do I convert watts to Btu per hour?

Multiply watts by 3.412. That factor comes from the standard conversion of 1 kilowatt-hour to 3,412 Btu. An 8,200 W heater produces about 27,980 Btu/h.

What is the best heater for a warehouse?

It depends on ceiling height, layout, and fuel. Overhead infrared heaters suit high-ceiling buildings because they heat people and floors instead of air that rises to the roof. Unit heaters are also widely used. For a full comparison, see [Internal link: How to Heat a Warehouse or Large Commercial Space].

Can a facility use different types of heaters in different areas?

Yes, and most do. A warehouse might use overhead IR on the floor, unit heaters at the docks, and electric heaters in offices.

What heater should I use if the building has no gas line?

Electric heaters need no fuel supply or venting. Where electrical capacity is limited and higher output is required, propane- or oil-fired heaters with on-site fuel storage are options.

When do I need a professional heat load calculation?

Get one for buildings with ceilings well above 8 feet, for large or poorly insulated spaces, and when selecting a facility's primary heating system. The per-square-foot estimate applies only to standard-height rooms.

References