By late October a normal night at BWI bottoms out at 46.5 degrees. By November it is 36.5. Those are the National Weather Service climate normals for Baltimore, and they are the reason so many good fall events quietly end an hour early with half the guests sitting in their coats.
Renting a heater looks like the obvious fix. It is only half of one. Figuring out how to heat a party tent means understanding what the heater needs from you before it can warm anything: a tent that is actually closed in, a place to plug in, and enough lead time that the unit is on the truck when the tent is. Skip the first one and the most powerful heater we own will blow warm air straight out into the yard.
📋 In This Guide
When You Need to Heat a Party Tent in Maryland
If your event runs past dark any time from October through April, whether it is a graduation party, a corporate evening, a fall fundraiser or a wedding, plan for heat. That is the short version, and the numbers behind it are not close.
The National Weather Service puts the normal low at BWI at 58.8 degrees in September, 46.5 in October and 36.5 in November. Guests do not experience the daytime high they saw in the forecast. They experience whatever it is at nine in the evening, standing still, three hours after the sun went down.
A tent does not help with this on its own. It blocks sun, rain and dew, but it carries no insulation at all, so an open sided tent on a cold night is the same temperature as the yard around it. Shade is free. Warmth is not.
How to Heat a Party Tent: Three Things Have to Be True
Heating a tent takes three things at once: sidewalls to close the space in, electricity to run the blower and thermostat, and propane to make the heat. Miss any one of the three and the heater cannot do its job, no matter how big it is.
Sidewalls come first. Our own guidance has been the same for years: close the tent in and leave no more than 10 to 20 feet of opening for people to come and go. Warm air does not stay under a canopy with four open sides any more than it stays in a house with the doors off. This is the step people try to skip, and it is the one that decides whether the heat works.
Power comes second, and it is modest: the blower and the thermostat run on a standard 120 volt household outlet, so no outlet within reach means a generator to work out early rather than on setup day.
Fuel comes third, and it is the easy one, because our propane heaters arrive with a 100 pound tank, the gas line and a thermostat already included.
If you are reading this in July and have the opposite problem, we cover fans, cooling units and airflow in our guide to heating and cooling a tent.
What Size Heater Do You Need?
Plan on one heater for every 1,000 to 1,500 square feet of tent. Use the 1,500 end for a mild evening in the forties and the 1,000 end when it is genuinely cold, because the colder it gets the harder each unit has to work to hold the same temperature.
That ratio is the one we actually quote from, and it turns a vague question into arithmetic: multiply the tent dimensions, divide, and round up.
| Tent size | Floor area | Heaters, mild night | Heaters, deep cold |
|---|---|---|---|
| 20 x 20 | 400 sq ft | 1 | 1 |
| 20 x 40 | 800 sq ft | 1 | 1 |
| 30 x 30 | 900 sq ft | 1 | 1 |
| 30 x 45 | 1,350 sq ft | 1 | 2 |
| 40 x 40 | 1,600 sq ft | 2 | 2 |
| 30 x 60 | 1,800 sq ft | 2 | 2 |
| 40 x 60 | 2,400 sq ft | 2 | 3 |
| 40 x 80 | 3,200 sq ft | 3 | 4 |
| 40 x 100 | 4,000 sq ft | 3 | 4 |
Unit size matters alongside unit count. Our 80,000 BTU heater is built for 20 foot wide tents, where the throw of the blower matches the span. Our 170,000 BTU unit is the one for the 40 foot wide frames and pole tents, and it is the workhorse on most large winter jobs. We also carry a 40,000 BTU unit for small spaces and an electric 20 kilowatt heater for the rare site that has heavy three phase power available.
If you have not settled on a tent size yet, start from your guest count: our capacity guides work through the seating math, including how many people fit under a 40 x 60 tent, and our tent inventory page shows the full range.
Why the Heater Sits Outside the Tent
The heater does not go inside the tent. The unit and its propane tank sit outside on the ground, and a vent blows the warm air under the sidewall into the space. People expect something tucked in a corner near the bar, and that is not how it works.
The reason is combustion. Anything burning fuel produces carbon monoxide, and the Consumer Product Safety Commission is blunt about the risk: people die every year from carbon monoxide poisoning caused by portable heaters used inside tents. Keeping the burner outside and ducting only the warm air in is what makes a closed, heated tent safe to stand in for five hours.
That changes what your site has to offer, because you need clear, level ground just outside the tent for the unit and the tank, somewhere guests are not walking, parking or smoking. The duct runs under one section of sidewall, so that stretch of wall is committed and cannot be your main entrance.
Noise is the part nobody plans for. These units run at about 70 decibels, roughly a loud conversation, and they cycle on and off all evening. If there are speeches, put the heater at the far end from the microphone.
What the Heater Draws and What It Burns
A propane tent heater needs far less electricity than people assume, because the propane makes the heat and the outlet only runs the blower and the thermostat.
Our 80,000 BTU unit draws 5 amps on startup and 1.5 amps running. The 170,000 BTU unit draws 7.3 on startup and 5 running. Both plug into a standard 120 volt outlet. The startup number is the one worth checking, because that brief spike is what trips a circuit already loaded with catering equipment or a band.
One detail catches people every season: the extension cord is not included. It is listed that way on the heater and it still gets missed, so work out the run from the outlet to the unit and bring a cord rated for it.
If the site has no usable outlet, a generator covers it. Our 2,000 watt quiet generator delivers 16.7 amps at 120 volts, which is comfortably more than either propane heater needs. Our 3,500 watt unit handles a heater plus lighting.
On fuel, the 80,000 BTU unit burns about 3.7 pounds of propane an hour at full output and the 170,000 BTU unit about 7.9 pounds, both varying with conditions. The included 100 pound tank gives an average run time of four to eight hours, and because the thermostat cycles the burner rather than running it flat out, a normal evening event sits inside that. Tanks can be connected together for a longer day.
The electric option is a different animal, because our 20 kilowatt electric heater needs a 240 volt, 48 amp three phase supply, which is a building service rather than anything a house can offer.
Sidewalls Are a Separate Rental
Sidewalls are rented by the panel, not bundled with the tent, and you need roughly one panel for every 15 to 20 feet of tent perimeter. This is the line item people forget when they budget for heat, and it is usually the larger part of the job.
The arithmetic is quick: a 40 by 60 tent has 200 feet of perimeter, so ten 20 foot panels close it in, while a 20 by 40 tent has 120 feet and takes six. Subtract a panel or two if you are leaving an entrance open, which you should.
Panels come in 15 and 20 foot lengths at 7 or 8 feet tall, and in three styles: solid, cathedral windowed and clear. For a heated evening event the windowed and clear panels earn their place, because a fully solid tent after dark feels like a box. Installation is included, so this is not something you are clipping on yourself in the cold. You can see the styles alongside the heaters and generators on our tent accessories page.
How to Heat a Party Tent on Short Notice (You Probably Cannot)
Decide about heat when you book the tent, not the week of the event, because heaters are a small fleet compared to tents and the first genuine cold snap of the season books out every unit in the region inside about two days. The week you most want a heater is the week nobody has one.
Sidewalls go the same way, a panel at a time. Our full timeline is in our guide to how far in advance to book a tent rental in Maryland.
Enclosing and heating a tent can also change how your county looks at it. A walled tent is treated differently from an open canopy in a lot of jurisdictions, and fuel fired equipment draws its own attention. Our Maryland tent permit guide covers the county by county picture, and the Maryland Office of the State Fire Marshal is the authority on permits and inspections for temporary structures.
Not sure how much heat your date and tent size call for? Send us the date, the guest count and where the tent is going, and we will work out the units, the sidewall count and the power. Get a quote.
Frequently Asked Questions
How many heaters do I need for a 20 x 40 tent?
One heater is enough, because a 20 by 40 tent is 800 square feet and that sits comfortably inside the 1,000 to 1,500 square feet a single unit covers. For a 20 foot wide tent the 80,000 BTU heater is the right match, since its blower is sized for that span. Add a second unit only if the tent is going up in a hard freeze or the site is badly exposed to wind.
Do I need sidewalls if I am using a tent heater?
Yes, and skipping them wastes the heater entirely, because the heat has nothing holding it in and the unit vents under a sidewall by design, so without walls there is nothing for it to vent under. Close the tent in, leave no more than 10 to 20 feet open for an entrance, and budget one panel for roughly every 15 to 20 feet of perimeter.
Can you use a propane heater inside an enclosed tent?
No, and this is the one to get right. Burning propane inside an enclosed tent produces carbon monoxide in the space your guests are standing in, and the Consumer Product Safety Commission records deaths from exactly that every year. Commercial tent heaters solve it by design: the burner and the tank stay outside and only heated air is ducted in. A patio heater or a camping heater brought in from home does not work that way and does not belong under a closed tent.
How far in advance should I book a tent heater?
Book it when you book the tent, because heater inventory is much smaller than tent inventory and a single cold forecast clears it out across the region in a couple of days. For any event between October and April, treat heat and sidewalls as part of the original order. Releasing them closer to the date is easy, and finding them during a cold snap is not.
Cold weather is not the thing that ruins an outdoor event. Being unprepared for it is. Once the tent is closed in and the heat is sized properly, an October evening under a tent is one of the best places in Maryland to be. Request your quote and we will size it with you.