How much does it cost to run a garage unit heater? The answer depends on the heater’s fuel type, input capacity, your local energy rate, how often the thermostat actually calls for heat, and how much heat the garage loses through walls, ceilings, doors, and air leakage.
As a rough starting point, an electric garage unit heater may cost anywhere from about $0.90 to $2.70 per hour while its heating elements are energized, depending on heater size and electricity rates. A natural-gas unit heater can often cost less per burner-on hour, while propane can be competitive or expensive depending heavily on local delivery prices.
The most important point is that a heater rarely runs at full output every minute that you are in the garage. A thermostat cycles the unit on and off. That means the cost to operate a heater for four hours is not necessarily the same as four full hours of fuel or electricity consumption.
This guide shows you how to calculate the operating cost of electric, natural-gas, and propane garage unit heaters using your own utility rates. It also explains which factors can make one garage cost dramatically more to heat than another, even when the heaters have similar output.
Quick Answer: Garage Unit Heater Running Cost
The table below uses simple example energy rates so you can see the general relationship between heater size and operating cost. These are illustrative examples only. Your actual utility or fuel bill should always be used for a final calculation.
| Heater Type | Example Size | Example Energy Rate | Approx. Cost While Heating |
|---|---|---|---|
| Electric | 5 kW | $0.18/kWh | $0.90/hour |
| Electric | 10 kW | $0.18/kWh | $1.80/hour |
| Electric | 15 kW | $0.18/kWh | $2.70/hour |
| Natural gas | 50,000 BTU input | $1.50/therm | $0.75/hour |
| Natural gas | 75,000 BTU input | $1.50/therm | $1.13/hour |
| Natural gas | 100,000 BTU input | $1.50/therm | $1.50/hour |
| Propane | 50,000 BTU input | $2.70/gallon | About $1.48/hour |
| Propane | 75,000 BTU input | $2.70/gallon | About $2.21/hour |
| Propane | 100,000 BTU input | $2.70/gallon | About $2.95/hour |
These figures represent approximate cost while the heater is actively producing heat at full input. Actual daily or monthly cost depends heavily on thermostat runtime.
The Three Numbers You Need Before Calculating Cost
You can estimate garage-heater operating cost with three basic pieces of information:
- The heater’s electrical kW rating or fuel input BTU rating
- Your local electricity, natural-gas, or propane price
- The approximate number of hours the heater actually runs
The first two are relatively easy to find. The third is where many inaccurate estimates come from.
If you spend six hours in your garage, the heater may not burn fuel or draw full heating power for all six hours. After the garage reaches the thermostat setting, the heater cycles. A well-insulated garage might require relatively short heating cycles. A drafty, uninsulated garage in subzero weather may keep the heater running almost continuously.
How to Calculate the Cost of an Electric Garage Unit Heater
Electric resistance unit heaters are straightforward to calculate because they are rated in kilowatts.
The formula is:
Heater kW × electricity rate per kWh × heater-on hours = operating cost
For example, suppose you have a 10 kW garage unit heater and your electricity costs $0.18 per kilowatt-hour.
10 kW × $0.18 = $1.80 per hour
If the heating elements remain on for three total hours during the day:
$1.80 × 3 = $5.40
That is the heating-energy cost for that day, excluding any special utility charges or demand charges that may apply to certain commercial accounts.
Electric Garage Heater Cost by Size
| Electric Heater Size | At $0.12/kWh | At $0.18/kWh | At $0.25/kWh |
|---|---|---|---|
| 5 kW | $0.60/hr | $0.90/hr | $1.25/hr |
| 7.5 kW | $0.90/hr | $1.35/hr | $1.88/hr |
| 10 kW | $1.20/hr | $1.80/hr | $2.50/hr |
| 12.5 kW | $1.50/hr | $2.25/hr | $3.13/hr |
| 15 kW | $1.80/hr | $2.70/hr | $3.75/hr |
Electricity prices vary substantially by state, utility, time-of-use plan, and season. Use the energy charge from your own electric bill whenever possible.
How to Calculate Natural-Gas Garage Unit Heater Cost
Natural-gas unit heaters are usually listed by BTU input. Residential natural gas is commonly billed in therms, CCF, or MCF depending on the utility.
One therm contains 100,000 BTU of energy. That makes a therm-based calculation particularly easy.
The formula is:
Heater input BTU ÷ 100,000 × gas price per therm × burner-on hours = operating cost
For example, a 75,000 BTU input heater consumes 0.75 therm per hour while the burner is operating.
If natural gas costs $1.50 per therm:
0.75 × $1.50 = $1.125 per burner-on hour
Rounded, that is approximately $1.13 per hour.
Natural-Gas Heater Cost by Input Capacity
| Gas Heater Input | At $1.00/therm | At $1.50/therm | At $2.00/therm |
|---|---|---|---|
| 30,000 BTU | $0.30/hr | $0.45/hr | $0.60/hr |
| 45,000 BTU | $0.45/hr | $0.68/hr | $0.90/hr |
| 50,000 BTU | $0.50/hr | $0.75/hr | $1.00/hr |
| 60,000 BTU | $0.60/hr | $0.90/hr | $1.20/hr |
| 75,000 BTU | $0.75/hr | $1.13/hr | $1.50/hr |
| 100,000 BTU | $1.00/hr | $1.50/hr | $2.00/hr |
| 125,000 BTU | $1.25/hr | $1.88/hr | $2.50/hr |
Gas unit heaters also use a small amount of electricity for the blower, ignition system, and controls. Compared with the fuel consumed by the burner, that electrical cost is usually relatively small, but it is still part of total operating cost.
If your utility bills natural gas in CCF or MCF instead of therms, check the bill for its heat-content conversion factor rather than assuming every cubic foot contains exactly the same amount of energy.
How to Calculate Propane Garage Unit Heater Cost
Propane is commonly sold by the gallon. One gallon of propane contains roughly 91,500 BTU of energy.
A practical formula is:
Heater input BTU ÷ 91,500 × propane price per gallon × burner-on hours = operating cost
Consider a 75,000 BTU propane unit heater with propane costing $2.70 per gallon.
75,000 ÷ 91,500 = approximately 0.82 gallon per hour
0.82 × $2.70 = approximately $2.21 per burner-on hour
Propane Garage Heater Cost by Size
| Propane Heater Input | Approx. Gallons/Hour | Cost at $2.25/gal | Cost at $2.70/gal | Cost at $3.50/gal |
|---|---|---|---|---|
| 30,000 BTU | 0.33 | $0.74/hr | $0.89/hr | $1.15/hr |
| 50,000 BTU | 0.55 | $1.23/hr | $1.48/hr | $1.91/hr |
| 75,000 BTU | 0.82 | $1.84/hr | $2.21/hr | $2.87/hr |
| 100,000 BTU | 1.09 | $2.46/hr | $2.95/hr | $3.83/hr |
| 125,000 BTU | 1.37 | $3.07/hr | $3.69/hr | $4.78/hr |
Propane prices vary by region, delivery volume, supplier, tank arrangement, and season, so local pricing is especially important.
Why “Cost Per Hour” Can Be Misleading
When people ask what a garage heater costs per hour, there are actually two different meanings.
One meaning is a full hour of burner or heating-element operation. The other is a clock hour while the thermostat maintains temperature, which can cost less because the heater cycles.
Suppose a 10 kW electric heater costs $1.80 per full heating hour. If the garage is already warm and the thermostat only energizes the heater for 30 minutes during a one-hour period, the effective cost for that clock hour is approximately $0.90.
This relationship is called duty cycle.
Understanding Heater Duty Cycle
Duty cycle is the percentage of time the heater actually produces heat.
| Duty Cycle | Heater-On Time During 4 Clock Hours | What It Suggests |
|---|---|---|
| 25% | 1 hour | Low heat loss or mild conditions |
| 50% | 2 hours | Moderate heat demand |
| 75% | 3 hours | High heat demand |
| 100% | 4 hours | Heater runs continuously |
Duty cycle changes with outdoor temperature, wind, garage-door use, thermostat setting, insulation, and stored heat. Estimate actual burner-on or element-on hours rather than simply counting time spent in the garage.
Example Monthly Operating Costs
Suppose the garage is occupied four hours per day, 30 days per month, but the heater averages a 50% duty cycle after warm-up. That equals approximately 60 full heating hours per month.
| Heater | Example Rate | Cost Per Full Heating Hour | Approx. Monthly Cost at 60 Heating Hours |
|---|---|---|---|
| 5 kW electric | $0.18/kWh | $0.90 | $54 |
| 10 kW electric | $0.18/kWh | $1.80 | $108 |
| 15 kW electric | $0.18/kWh | $2.70 | $162 |
| 50,000 BTU natural gas | $1.50/therm | $0.75 | $45 |
| 75,000 BTU natural gas | $1.50/therm | $1.13 | About $68 |
| 100,000 BTU natural gas | $1.50/therm | $1.50 | $90 |
| 50,000 BTU propane | $2.70/gal | $1.48 | About $89 |
| 75,000 BTU propane | $2.70/gal | $2.21 | About $133 |
| 100,000 BTU propane | $2.70/gal | $2.95 | About $177 |
Again, these are examples rather than promises about what your garage will cost to heat. A poorly insulated garage may average a much higher duty cycle. A well-insulated garage may average much lower.
Does a Bigger Garage Unit Heater Always Cost More to Run?
A larger heater consumes more energy per minute while it is firing, but that does not automatically mean it will use proportionally more energy over an entire month.
Imagine a garage that needs a certain amount of heat to maintain 55°F. A larger heater may deliver that heat faster and shut off sooner. A smaller heater may run longer.
The building’s heat loss is the underlying demand.
However, this does not mean oversizing has no consequences. A substantially oversized unit can short-cycle, create greater temperature swings, produce more airflow than necessary, and potentially operate less efficiently in real-world conditions.
Correct sizing remains important. The goal is enough capacity to meet the garage’s design heat loss without going dramatically beyond what the space requires.
Input BTU, Output BTU, and Efficiency
For fuel-fired unit heaters, the BTU number used in the operating-cost formula should normally be the fuel input rating because that represents how much fuel energy the burner consumes.
Heat output is lower than input because no combustion heater is perfectly efficient.
For example, a 100,000 BTU input heater operating at 80% thermal efficiency delivers roughly 80,000 BTU of useful heat.
If another heater has the same 100,000 BTU input but higher thermal efficiency, it can deliver more useful heat from the same amount of fuel.
When comparing operating costs between gas-fired models, do not compare input capacity alone. Compare useful output, efficiency, and how well the heater size matches the garage.
Why Insulation Has Such a Large Effect on Operating Cost
Once you have selected a reasonable heater, the garage itself often has a greater effect on monthly energy cost than small differences between heater models.
Heat escapes through:
- Exterior walls
- Ceilings and roofs
- Garage doors
- Windows
- Exterior service doors
- Cracks and air leaks
- Unsealed penetrations
If the garage loses heat rapidly, the thermostat calls for heat more often. That raises the duty cycle and therefore the monthly bill.
An insulated overhead door, proper weatherstripping, ceiling insulation, wall insulation, and basic air sealing can reduce the amount of time the heater needs to operate.
Garage Door Openings Can Change the Math Quickly
Opening a large overhead door can release a significant amount of warm air and replace it with cold outdoor air in a matter of moments.
A garage used for occasional weekend projects may only open its door a few times per day. A repair shop or frequently used residential garage may open it dozens of times.
Every opening creates a recovery load.
This is one reason two otherwise identical garages can have very different fuel bills. The building dimensions may be the same, but their operating patterns are not.
Your Thermostat Setting Matters
Maintaining a garage at 45°F typically requires less energy than maintaining it at 65°F during the same outdoor conditions.
The larger the difference between indoor and outdoor temperature, the faster heat tends to leave the building.
If the garage is primarily used to prevent freezing or keep vehicles above extreme cold, a lower thermostat setting may provide significant savings compared with maintaining living-space temperatures.
If you use the garage as a workshop, you may decide the added comfort is worth the additional cost. The key is understanding that thermostat setting is part of the operating-cost equation.
Occasional Heating vs. Maintaining Temperature All Winter
There are two common approaches to heating a garage.
Maintaining a Lower Temperature Continuously
The heater keeps the garage above a chosen baseline temperature all winter. This may help protect stored liquids, tools, plumbing, or equipment from extreme cold.
The benefit is that the building and everything inside it remain relatively warm. The downside is that heat loss continues 24 hours per day.
Heating Only When the Garage Is Occupied
The thermostat is lowered when the garage is not in use and increased before or during work sessions.
This can reduce total heating hours, but recovery may require the heater to run continuously for a period because it must warm not only the air but also the concrete floor, walls, vehicles, tools, and equipment.
Which strategy costs less depends on climate, insulation, usage, and the minimum temperature you need to maintain.
Natural Gas vs. Electric vs. Propane: Which Is Cheapest to Operate?
There is no universal winner because energy prices vary dramatically by region.
Natural gas often has a lower fuel cost per unit of heat in areas where residential gas service is already available. Electric resistance heaters can be more expensive to operate where electricity rates are high, but they eliminate combustion venting and gas delivery. Propane can be practical where natural gas is unavailable, but its delivered price can fluctuate substantially.
The best comparison is to calculate the cost of usable heat with your own rates rather than assuming one fuel is always cheaper.
| Factor | Electric | Natural Gas | Propane |
|---|---|---|---|
| Rate to check | $/kWh | $/therm or utility equivalent | $/gallon |
| Cost calculation | Very simple | Simple once billing units are known | Simple using BTU per gallon |
| Fuel delivery | Electrical service | Gas utility line | Storage tank and deliveries |
| Price variability | Varies by utility | Varies by utility and season | Can vary significantly by supplier and season |
| Extra operating load | Fan included in electrical draw | Small electrical blower/control load | Small electrical blower/control load |
Do 240-Volt Electric Garage Heaters Cost More Than 120-Volt Heaters?
Voltage by itself does not determine energy cost.
Your electric utility charges for energy in kilowatt-hours, not simply for voltage.
A 5 kW heater uses approximately 5 kWh when operating at full output for one hour whether the equipment is designed around a particular 240-volt circuit configuration or another compatible electrical arrangement.
Higher-voltage unit heaters are common because delivering substantial heating power at lower current can make more sense electrically. But the operating cost still comes back to kilowatts multiplied by your electricity rate and runtime.
How to Estimate Your Own Monthly Garage Heating Bill
Use the following process rather than relying on a generic online estimate.
- Find the heater’s kW rating or fuel input BTU rating.
- Find your actual energy rate from your electric bill, gas bill, or propane supplier.
- Calculate the cost for one full heating hour.
- Estimate how many hours per day the heater actually produces heat.
- Multiply by the number of days you expect to use the heater.
- Repeat the estimate for mild and very cold weather so you have a realistic range.
If you do not know the duty cycle, start with several scenarios such as 25%, 50%, and 75% rather than assuming the heater will run continuously.
How to Reduce Garage Unit Heater Operating Costs
The most effective savings usually come from reducing heat loss or unnecessary runtime.
- Insulate exterior walls and the ceiling where practical.
- Use insulated garage doors.
- Replace damaged weatherstripping around overhead doors.
- Seal obvious drafts and penetrations.
- Use a thermostat rather than manually running the heater continuously.
- Lower the thermostat when the garage does not need full comfort temperature.
- Avoid leaving overhead doors open longer than necessary.
- Keep the heater clean and maintained according to the manufacturer.
- Make sure warm discharge air is directed into the occupied space rather than immediately toward the thermostat.
- Consider air circulation in high-ceiling garages to reduce excessive heat stratification.
Buying a slightly more efficient heater can help, but reducing building heat loss can often produce savings every hour the heater operates.
Fixed Utility Charges vs. Actual Heater Energy Cost
One detail frequently overlooked in operating-cost comparisons is the fixed monthly charge on a utility bill.
If your home already has natural-gas service, a garage heater may simply add fuel consumption to an existing bill. If gas service would exist only for the garage, fixed utility charges can materially change the economics. Propane tank rental, delivery minimums, electrical upgrades, and commercial demand charges can have a similar effect.
Operating Cost Is Different From Total Cost of Ownership
The cheapest heater to run is not automatically the cheapest heater to own.
Total cost of ownership can include:
- Purchase price
- Electrical installation
- Gas piping
- Venting
- Propane tank installation or rental
- Permits
- Maintenance
- Repairs
- Energy or fuel
A higher hourly energy cost can still make sense when installation is much cheaper. Conversely, lower fuel cost can matter more in a large garage heated for many winter hours.
Frequently Asked Questions
How much does a 5 kW garage heater cost to run?
Multiply 5 kW by your electricity rate. At $0.18 per kWh, a 5 kW heater costs approximately $0.90 for each full hour that the heating elements operate.
How much does a 10 kW garage heater cost to run?
At $0.18 per kWh, a 10 kW electric garage heater costs approximately $1.80 per full heating hour. If it averages a 50% duty cycle during a four-hour garage session, it would use approximately two full heating hours, or about $3.60 in this example.
How much natural gas does a 50,000 BTU garage heater use?
A 50,000 BTU input heater consumes approximately half of a therm of natural-gas energy per burner-on hour. At $1.50 per therm, that equals about $0.75 per hour for the gas itself.
How much propane does a 50,000 BTU garage heater use?
Using approximately 91,500 BTU per gallon of propane, a 50,000 BTU input heater can use roughly 0.55 gallon per burner-on hour at full input.
Is it expensive to heat a garage all winter?
It can be, particularly if the garage is large, poorly insulated, maintained at a high temperature, or located in a severe winter climate. A well-insulated garage maintained at a modest temperature can cost considerably less because the heater runs fewer hours.
Does turning the thermostat down save money?
Generally, yes. A lower indoor temperature reduces the temperature difference between the garage and outdoors, which usually reduces heat loss and heater runtime.
Is natural gas cheaper than electric heat for a garage?
Often, but not always. The correct answer depends on local electricity and gas prices, equipment efficiency, installation costs, and how many hours the garage is heated. Use your own utility rates for a meaningful comparison.
Final Thoughts
The cost to run a garage unit heater is not determined by heater size alone. Your energy rate, fuel type, thermostat setting, climate, insulation, ceiling height, garage-door use, and actual heater runtime all matter.
For electric heaters, calculate cost by multiplying kilowatts by your electricity rate and heating hours. For natural gas, convert the heater’s BTU input into therms and multiply by your gas rate. For propane, divide BTU input by roughly 91,500 BTU per gallon and multiply by your delivered propane price.
Most importantly, distinguish between an hour that you are in the garage and an hour that the heater is actually firing. Thermostat duty cycle can make the difference between a realistic monthly estimate and one that is far too high or too low.
If your goal is to reduce the monthly bill, begin with the garage itself. Proper insulation, air sealing, an insulated overhead door, sensible thermostat settings, and correctly sized equipment can reduce how often the heater has to operate regardless of which fuel you choose.