How Many BTUs and Patio Heaters Do I Need for My Patio

Outdoor living spaces, like patios, gardens, and finished decks are not only trendy but they’re good for us. When we spend time outdoors with friends and family, we’re more likely to connect, laugh, and bond. In colder months, don’t let the drab weather drag you back inside. Turning your patio into a cozy backyard retreat is easy with a patio heater or outdoor fireplace from

When shopping for a heater, you may notice that most heaters list BTU, or British thermal units, along with how much space a heater can cover. We’re going to cover what BTU’s are and how to determine how many you need for your patio.

What is a British Thermal Unit (BTU)?

BTU stands for British Thermal Unit. It is the imperial system’s basic unit of heat, used to measure how much heat is required to raise one pound of water’s temperature by one degree. Heating and cooling appliances are usually marked with BTU’s to let buyers know what size space they will be best for. The heat output of a fireplace or heater is measured per hour in BTU’s.

Close up of patio heater

Calculate how many BTU’s you need

The formula for calculating BTU’s needed to heat any space is relatively simple. Don’t worry, you won’t need a graphing calculator, years of training, or any special equipment. First, you need to know how big your patio is, multiplying length x width to calculate square footage. Since patios are usually square or rectangular, this method will work for most homes.

Length X Width = Area
20 BTU x Area2
Simply multiply square footage by 20 BTU’s per square foot.

How Many Heaters Do I Need?

Let’s say your patio is 500 square feet. Look for a patio heater that provides 10,000 BTU’s. If your patio is larger that 500 square feet, or unusually shaped, consider several smaller heaters. With one large heater, the heat is concentrated , which can leave areas of the patio cold. Strategically placing heaters will keep you and your guests nice and toasty.

Other Factors

Patios require some different considerations for heating that other parts of your home. Since patios are open, they do not retain heat as well as an enclosed room. This affects the BTU’s you’ll need. If your patio or deck does not have a roof or cover, heating it efficiently requires more BTU’s. Other things to consider include the direction your patio faces—does it get a lot of sun—and the climate you live in.

  • Colder Climate = 50-60 BTU’s
  • Warmer Climate = 30-35 BTU’s

Nights under the stars will be much cozier now with a heater to keep you warm. Gather friends to roast marshmallows on a firepit, or tell ghost stories around the fireplace. At, we have electric fireplaces and heaters for every room in your home, even the outdoor spaces. Enjoy our affordable prices year-round, with free shipping!

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Learn More

  1. Do Patio Heaters Really Work?
  2. Patio Heater Buying Guide
  3. Calculating BTU’s Per Square Foot
  4. Determining How Mandy BTUs Your Home Needs
  5. Understanding BTU Readings – The Simplified Version