On air conditioners and heaters, it’s common to see a BTU rating listed among the specifications. But what is BTU, and how does it affect which heater you should choose?
The British thermal unit, or BTU, is how HVAC units measure an appliance’s capacity for heating or cooling a space. The number reflects the energy needed to raise a pound of water by one degree Fahrenheit.
As it relates to patio heaters, the BTU rating gives you an idea of how much heat the appliance puts out and how much energy it consumes. As such, a higher BTU heater has more heating power. However, more isn’t necessarily better for your space.
If you’ve ever wondered, “How many BTU do I need to heat my patio?” you’ve come to the right place. In this guide, you’ll find out how to use BTU to choose the right patio heater for your outdoor area.
The size of the area you need to heat is one of the biggest factors that determines how many BTU for patio heater is ideal. There are other factors that will affect the BTU needed, but this is a rough estimate for different patio sizes:
Some of the other factors that can affect heat retention include:
To determine the appropriate patio heater BTU rating for your space, the first step is to identify the square footage. If you don’t already know how many square feet your patio is, measure its length and width, then multiply the two numbers.
As a general rule, 20-30 BTU per square foot is a good starting point for choosing a patio heater. However, that number can vary based on factors like the climate where you live and the layout of your patio. If you live in an area with mild winters, 20 BTU per square foot may be plenty for your space. For an open, uncovered patio in New England, you may need as much as 50 BTU per square foot to keep your patio warm in the winter.
Choosing the right patio heater isn’t always as simple as calculating how many BTU per square foot is ideal. While square footage is a good starting point, ceiling height also plays a factor. A space with a high ceiling or pergola has more air to heat than a space with a lower ceiling.
To maintain warmth in an outdoor space with high ceilings, you’ll likely need a higher BTU rating or multiple heaters. It’s also a good idea to choose ceiling-mounted patio heaters, which are designed to direct heat downward from above.
Different styles of outdoor heaters will offer different BTU ranges. As a result, no one type of heater works for every space. Here are the main categories of patio heaters you have to choose from:
Tabletop heaters can be electric or gas-powered, and you can even choose a firepit table like the Olympus Athena Fire Table, which can add to the ambiance of your patio. However, they aren’t appropriate for heating a large area. Tabletop heaters are ideal for an outdoor bistro or dining area where people are likely to sit around them.
A propane heater radiates heat outward and down to provide coverage over a wide area. Freestanding propane heaters use either a reflector to direct heat down in all directions or a panel for more directional heating.
The Bromic Tungsten Portable Gas heater, for example, has a tilting head design so you can point the heat where you want it and adjust as needed. The wind-resistant design also makes directional heaters a good choice for open patios where it can get breezy.
These electric heaters can be mounted either on the ceiling or high up on a wall. Heat naturally rises, so directing the heat downward helps it stay at ground level, where it can keep the patio area warm more easily.
Electric heaters use watts to measure heating capacity instead of BTU. The wattage reflects how much electricity the heater uses, and therefore how quickly it can heat a space. One watt is equal to roughly 3.41 BTU/hr. So, a 6000 watt heater, like the Bromic Heating Tungsten Electric 6,000-watt heater, provides roughly 20472.85 BTU/hr.
In general, you should match the BTU of your patio heater to the intended use. If you want to cover an entire backyard, you’ll likely want one or more larger propane heaters. For a smaller, covered outdoor dining area, a tabletop heater may be plenty.
There are many options for heating an outdoor space. The right BTU rating depends on the size and layout of your space, as well as the climate in your area. If you need more assistance choosing the best patio heater for your space, the friendly team at Patio Heat and Shade is ready to help. Take a look at the extensive collection of ceiling-mounted heaters available today.
A: BTU measures the heating capacity of a patio heater — more BTU means more heat.
A: Generally, 20–30 BTUs per square foot is a good starting point, but you may need more or less depending on the climate and the layout of your patio.
A: A higher BTU rating isn’t always a better choice. Too much heat in a small area can waste energy and make the space too hot to be comfortable.
A: To get the most out of your heater, use screens or dividers to block wind, add coverings or walls, and place the heater near seating zones for the best heat retention.