A 1500W garage heater is the cheapest of these three sizes to run, a 5000W heater costs much more per hour but can heat a larger space effectively, and a 7500W heater is the most expensive to operate but is often used where stronger output is necessary. The real cost depends on your electricity rate and how many hours the heater actually runs, but the basic pattern is simple: the higher the wattage, the higher the running cost.
At a rough electricity rate of $0.15 per kWh, a 1500W heater costs about $0.23 per hour, a 5000W heater costs about $0.75 per hour, and a 7500W heater costs about $1.13 per hour if they run continuously. That gives you a practical starting point, but the real monthly cost depends on whether the heater cycles on and off through a thermostat or runs close to full output for long periods in a cold garage.
Use the calculator below to estimate your exact running cost based on your heater size and electricity rate.
What each heater size usually costs to run
A simple way to compare these heaters is to look at hourly and daily cost side by side. A 1500W heater uses 1.5 kWh per hour, so it is usually the most affordable option to run. That makes it a reasonable choice for spot heating, short work sessions, or smaller garages where you do not need heavy-duty output. The trade-off is that it may struggle if the garage is large, very cold, or poorly insulated.
A 5000W heater uses 5 kWh per hour, and a 7500W heater uses 7.5 kWh per hour. That raises the running cost quickly, but these larger heaters are designed for bigger spaces or colder conditions. In other words, the more expensive heater is not automatically the worse choice. If it heats the space properly and cycles normally, it may be more practical than using a smaller heater that runs nonstop and still leaves the garage cold.
- 1500W heater at $0.15 per kWh: about $0.23 per hour
- 5000W heater at $0.15 per kWh: about $0.75 per hour
- 7500W heater at $0.15 per kWh: about $1.13 per hour
- At 8 hours of continuous use, that works out to about $1.80, $6.00, and $9.00 per day
If you want a deeper look at exact garage sizing before comparing costs, it helps to read what size electric heater do I need for my garage so you are matching the running cost to a heater that actually suits the space.
Why the real cost can be higher or lower than the basic math
The hourly figures above assume the heater runs at full power the whole time. In real garages, that is not always what happens. Once the space reaches the thermostat setting, the heater often cycles on and off, which lowers the true average cost. That is why a garage heater that looks expensive on paper may cost less than expected in an insulated attached garage used only for a few hours at a time.
On the other hand, a drafty detached garage can push the real cost much higher because the heater runs longer and works harder to hold the temperature. A small 1500W heater might look cheap to run, but if it never really catches up in cold weather, it may stay on nearly all the time and still not heat the space well. A larger 5000W or 7500W unit costs more per hour, but it may warm the garage faster and maintain a usable temperature more effectively.
The most useful way to think about running cost is not just price per hour, but price for the result you want. A small heater makes sense for lighter use and small spaces. A 5000W or 7500W heater makes more sense when garage size, climate, and insulation demand stronger output. The cheapest heater to run is not always the most practical heater to own.
You can calculate your exact running cost based on your heater size and electricity rate using this garage heater cost calculator.