Heating a 375 sq ft garage can cost anywhere from a few dollars per day to well over $200 per month, depending on the heater size, electricity rate, insulation level, and how long the heater runs. In many cases, the biggest factor is not just the garage size itself, but whether the heater is powerful enough to warm the space efficiently without running nonstop.
A small 1500W heater is usually cheap to run per hour but may struggle to heat a full 375 sq ft garage in cold weather. A 5000W heater costs more to operate but is often a more realistic fit for this size of garage, especially if the space is detached, uninsulated, or exposed to winter conditions. The right answer depends on how warm you want the garage and how well it holds heat.
Use the calculator below to estimate your exact running cost based on your heater size and electricity rate
What a 375 sq ft garage usually costs to heat
A quick way to estimate running cost is to multiply the heater wattage by your electricity rate. At $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. For a 375 sq ft garage, those numbers matter because this size is often right on the edge where a small heater may be underpowered and a medium heater starts making more practical sense.
If you use a 1500W heater for 8 hours a day, the full-output cost is only about $1.80 per day, but that does not mean it will heat the whole garage well. In mild conditions, it may be enough for light spot heating or for keeping part of the space more comfortable while you work nearby. In colder conditions, it may run nearly all the time and still leave the garage chilly. A 5000W heater at the same rate costs about $6.00 per day for 8 hours at full output, but it has a much better chance of actually warming the entire space. That is why the cheapest hourly cost is not always the best real-world value.
A 7500W heater may be used in a 375 sq ft garage, but it is usually more common where winters are harsher, ceiling height is greater, or insulation is poor. It will cost more to run, but it may also warm the garage much faster and cycle off sooner once the thermostat setting is reached. That makes it important to look beyond raw hourly cost alone.
For a more accurate estimate based on your actual usage, try this garage heater running cost calculator.
Why insulation and winter conditions change the real cost
Garage size gives you a starting point, but insulation often determines whether heating cost stays reasonable or climbs quickly. A 375 sq ft attached garage with insulated walls, a ceiling above it, and minimal drafts is much easier to heat than a detached garage with exposed walls and gaps around the door. In the better-insulated space, the heater can warm the garage and then cycle on and off. In the draftier space, it may run much longer and stay closer to full power.
This is also where local climate matters. In mild weather, a 5000W heater may only need to run part of the time to hold a workable temperature. In deeper winter conditions, especially if the garage starts out very cold, the same heater may run hard for long stretches. That is why monthly cost can vary so much from one homeowner to another. The garage may be the same size on paper, but the conditions inside are completely different.
If you are trying to estimate cost more accurately, it helps to match heater size to the garage first and then think about runtime second. A useful starting point is how many watts to heat a garage, because once you know the likely wattage range for 375 sq ft, the running cost becomes much easier to judge realistically.
What heater size makes the most sense for 375 sq ft
For most 375 sq ft garages, a 1500W heater is usually too small if your goal is to heat the whole space in winter. It can still be useful for targeted warmth near a bench or work area, but many homeowners find it does not deliver enough heat for the entire garage unless conditions are mild. That often leads to long runtimes, limited comfort, and a setup that feels cheap to run but underwhelming to use.
A 5000W heater is often the more balanced option for this garage size because it can provide stronger output without immediately jumping to the highest running cost bracket. In many cases, it gives a better mix of heating ability and manageable operating cost. A 7500W unit may still make sense if the garage is poorly insulated, detached, or located in a colder region, but it is usually chosen because the conditions demand it rather than because the floor size alone requires it.
The most practical approach is to judge cost in terms of usable heat, not just cents per hour. For a 375 sq ft garage, the best value often comes from choosing a heater that can warm the space properly and then cycle normally, rather than picking the smallest heater and hoping its low hourly rate makes up for weak performance.