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Unit Heater Buyer’s Guide

Unit Heater Buyer’s Guide

Unit Heater Buyer’s Guide

A dependable shop heater is essential. It should do its job quietly and should hardly be noticed.

The following guide should give you some information that can save you some time, and money.
The first consideration with buying a garage or shop heater is the size of the area to be heated. And think cubic feet, not square feet. Measure the size of your shop in square footage first, and then account for ceiling height.

You can expect to need 1 BTU per 20 square feet for a shop with a modest ceiling height (8-10 feet). But for taller ceilings you need to adjust to 1 BTU per 17 square feet. Other factors, such as insulation and your geographic location will need to be factored in. Then comes the comfort level you desire. If you spend long hours in the shop, you should want the shop to be as comfortable as your home is. If most of your garage visits are brief, perhaps you can get by with a “comfortably cool” environment.
Most garage and shop heaters are forced-air heaters, meaning they force heat into the area through the use of powerful fans. These make quick work to rid the shop of an overnight cool-down. Convection type heaters allow the heat to gently and naturally radiate into the room. Radiant heaters also lack a fan but rather “bounce” the heat into a room via polished reflectors.
These heaters typically come in three basic fuel types – natural gas, liquid propane, or electric – and each fuel type has advantages and disadvantages. Alternatively, customers also have a preference for wood stoves for certain applications. 


Currently the most popular, electric garage heaters provide the simplest solution to most heating needs. Requiring only a dedicated power circuit, and no need for venting, electric heaters come the closest to the plug-and-play device most homeowners seem to prefer.
For a garage of normal dimensions, 240 volts of power are required. Additionally, the line serving the heater should be dedicated, meaning that no other device is being fed by the same circuit. A certified electrician should be hired to run a dedicated service line.

Natural Gas

For maximum efficiency – meaning you get the heat you pay for with as little waste as possible – natural gas is the best option. Since you connect directly to a gas line, there is no refueling needed, and maintenance is minimal.
Ideally, you should install a natural gas heater on a ceiling joist in a corner of your shop. If you have sized it right, it shouldn’t matter how far from the work area it rests. Larger heaters can weigh over 100 pounds, so a block and tackle system would be needed to get it up to the ceiling. Research thoroughly to make sure you get a heater whose installation is within reach of your handyman skills.

If you don’t have a gas line already serving the garage, you’ll need to have one installed by a licensed gas technician. Flexible gas tubing can be used to reach the heater, a convenient addition not available in the past.

Natural gas heaters must vent through the roof, so part of the installation process will involve cutting a hole in the roof directly above the flue from the heater. Your venting kit will include flashing to make the cutout rain-proof. Ideally, the flue should be double walled, which provides clearance between the hot inner pipe and any combustible material.

Liquid Propane
Propane has proven to be versatile and dependable, making it a great choice for a shop heater. It’s a liquid when stored but expands as a gas when released.
If natural gas is unavailable at your residence, or if natural gas is prohibitively more expensive in your market, you should consider propane for your garage or shop heater. Both open flame and enclosed flame versions burn clean and don’t require as much venting as natural gas heaters.
Propane shop heaters must be vented. Carbon monoxide poses a very real danger with any device that derives oxygen from the air, and its colorless, mostly odorless presence exacerbates the threat. Portable propane heaters, despite being equipped with oxygen sensors, can still pose a danger in an enclosed area.


The most popular name in gas-fueled garage and shop heaters is Modine, and for good reason. These are hard-working, dependable, and durable. Another quality brand for gas heaters is Reznor, known for its line of energy efficient marvels and a long company history of success.

Both of these brands also manufacture electric models to the same level of quality as their gas-fueled units.

Frequently Asked Questions

Are unit heaters efficient?

Unit heaters are efficient, but some models out-perform others by a substantial margin in that regard. In simple terms, efficiency is getting what you pay for in energy consumption. In the realm of shop heaters, the more efficient a unit is, the more heat is delivered where it’s wanted. Heat loss is minimized in the more efficient devices.

What is the most efficient garage or shop heater?

The most efficient garage or shop heater is a gas fueled unit. Typically, garage heaters are not as efficient as residential furnaces, but the best models have efficiency ratings above 80 percent, some into the low 90s. This simply means that 80-90 percent of the money you spend on energy directly converts to heat, with as little loss as possible.

How do I install a garage or shop heater?

You install a garage or shop heater in a number of ways, but the most popular types mount near the ceiling on ceiling joists. Mounting brackets and hardware are included in most models, and should be used exactly as prescribed in the installation manual. Natural gas units must be vented through a pipe that extends above the roof, and electric units should have a dedicated 240-volt service line.

How many BTUs do I need?

You need one BTU per 20 square feet for areas with a standard ceiling (8-10 feet), and one BTU per 17 square feet for areas with a tall ceiling. If you live in a northern zone, you should tweak the unit size upward accordingly, and if your shop is not particularly well-insulated, you should account for heat loss.

Are unit heaters safe?

Unit heaters are very safe if used as directed. Some propane heaters include sensors to monitor oxygen content in the area as a safeguard against carbon monoxide poisoning. With appropriate spacing between the heater and combustible materials, the fire hazard is greatly reduced.

Which fuel type should I buy?

You should buy the fuel type that corresponds best to your needs and your budget. Natural gas and propane units create greater BTU output, but electric is much easier to install and maintain. Energy efficiency is good with all three types when premium products are installed.

How much does it cost to run a garage heater?

It costs approximately $0.28/hour to run a typical natural gas or propane heater and approximately $0.40/hour to run an electric heater on a 240-volt circuit, but many factors can alter those numbers substantially. Geographic location, quality/quantity of insulation, cost of utilities in your area, thermostat settings and the way the heaters are installed can all affect operating costs.

May 23, 2022
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