There are many factors that influence how quickly a room can heat up. It is therefore almost impossible to calculate this for someone’s specific situation. However, this article includes a calculator to find out how long it takes to heat up your room based on a few assumptions.
Additionally, this article includes the heat-up time for a standard US living room with a standard 1500 watt infrared heater as well as the proper amount of watts required (2300 W).
It will take an infrared heating system of 1500 watts approximately 5 minutes to heat an average-sized 330 square foot room from 50 °F (10 °C) to 68 °F (20 °C). Factors such as insulation, outdoor temperature, objects in the room, and humidity levels increase the time needed to heat the room.
Here are my heat-up time calculators for feet and meters
You will need to fill in:
- the total wattage of infrared heating you are planning to use
- the length, width, and height of the room in feet (left calculator) or meters (right calculator)
Infrared heaters require fewer watts for the same heating
The heat-up time by infrared heaters is the same as with conventional heating systems. However, infrared heating is a more efficient way of heating. Therefore, the amount of watts needed to heat a room is about 40% less. You can read all about infrared heating efficiency in my article: Everything I learned about infrared heating efficiency.
The heat-up calculator runs on a few assumptions
There are too many factors that influence the heat-up time that I had to make several assumptions and leave out unknown aspects of the room.
I made the following assumptions:
- heating the room means increasing the temperature by 18 degrees Fahrenheit (10 °C)
- an infrared heater is 40% more efficient than conventional heating systems
The following aspects were not taken into account:
- insulation value of the room
- objects in the room
- starting temperature
- humidity levels of the air
These aspects are different for every room and every house. They are even different over the day. Additionally, something like the exact insulation value is very hard to determine.
A 1500 watt heater in a standard living room
Most portable infrared heaters on the market are 1500 W. So we have:
- 1500 watts of infrared heating
- 2970 cubic feet room (984 cubic meters)
Here’s the heat-up time:
So, it takes a 1500 watts infrared heater approximately 5 minutes to heat an average-sized living room from a cold morning temperature to a comfortable room temperature. However, as mentioned before, this calculation is done by leaving out many relevant factors such as humidity levels and the presence of furniture. Therefore, these 5 minutes are only an estimation. The actual time it will take depends on your specific situation and will take longer than 5 minutes.
How long does it take with the proper amount of heating? (2300 W for 330 square feet)
The calculation above assumed the use of one 1500 W infrared heater. However, a room of 330 square feet normally requires a bit more watts. A general rule of thumb for heating requirements is 10 watts per square feet. That means you will need 3300 watts to heat this room.
However, infrared heaters are much more effective heaters and require about 40% less energy to create the same level of comfort. Therefore, 2300 watts of infrared heating is sufficient for a 330 square foot room. You can read all about why infrared heating is so much more efficient in my article: Infrared heaters energy use.
So, how long does it take for 2300 watts of infrared heating to heat a 330 square feet room?
- Room size: 2970 cubic feet (84 cubic meters)
- 2300 W of infrared are as effective as 3300 W regular heater
So, it takes 3,5 minutes for proper infrared heating (2300 W for 330 square feet) to heat the room. Again, this calculation did not take into account many relevant factors and should therefore only be used as a general indication of the absolute minimum time required to heat the room.
How to calculate the heat-up time for your room by yourself
The calculation above assumed a standard-sized living room. To be able to calculate the heat-up time for your own room by yourself, you will need to know the size of your room in cubic feet. You can calculate this by measuring the floor area of your room and multiply this by the height. So for example, if your room is 10 feet long and 10 feet wide with a ceiling of 9 feet, you will have 10 x 10 x 9 = 900 cubic feet.
Additionally, you will need to look at how many watts your infrared heater has. This is most likely 1500 W since almost all portable infrared space heaters have this wattage.
Steps of calculation:
- divide the number 840 by the amount of watts you have (this will give you a number in seconds)
- divide the number 35 by the outcome (this will get you the seconds needed to increase 1,8 Fahrenheit (1 °C)
- take your room size in cubic feet, and
- divide this by the seconds you just calculated (this will give the seconds needed to heat the entire room by 1,8 Fahrenheit (1 °C)
- multiply this number by the number of degrees you want the room to increase, and you will have the time needed to heat your room.
- multiply this number by 0,6 to get a better indication of how long it takes infrared heaters to heat a room to a comfortable level.
- 840 / 1500 W = 0,56 seconds (840 is the joules required to heat 1 cubic feet of air by 1 °C)
- 35 / 0,56 = 62,5 seconds
- 900 cubic feet room
- 900 cubic feet / 62,5 seconds = 14,4 seconds
- to increase the room 18 degrees Fahrenheit: 14,4 x 10 = 144 seconds. Which is a little over 2 minutes.
- 144 seconds x 0,6 = 86,4 seconds, or 1,44 minutes.
Infrared heaters actually do not heat the air in a room, but rather the people and objects inside it. Therefore, they are much more effective at creating a comfortable level of warmth. This does, however, not directly mean a room temperature increase. Please read my article if you want to know why. Everything I know about infrared heating efficiency.
How many watts do you need per room?
In general, when you have more heating capacity (wattage), the time needed to heat up a room is reduced. However, there is a recommended minimum of watts per room. This differs between regular heaters and infrared heaters since infrared provides more effective heating.
The following table shows the amount of wattage required per room for infrared heaters as well as regular space heaters. The wattage is different since not every room needs the same amount of heating due to different temperature requirements and other factors such as humidity levels. A bedroom for example should be colder than the living room for the best sleep.
|Area||Infrared heating: wattage |
per sq. ft (0,1 m²)
|Regular heating: wattage |
per sq. ft (0,1 m²)
|Living room||7 W||10 W|
|Bedroom||4.5 W||6.3 W|
|Bathroom||9.3 W||13.3 W|
|Closed porch||9.3 W||13.3 W|
|Open outdoor area||28 – 56 W||Warm air cannot heat an outdoor area|