Patio heaters are umbrella or mushroom shaped heaters which evolved from regular space heaters and propane shop heaters. They can be either gas or electric, floor, or table mounted, and some can be used safely indoors as well as outdoors.
These units all work on the principle of reflected heat being cast downwards to where people might be sitting or standing. Larger gas powered units may give off 40,000 BTUs of heat, or more, while smaller units, particularly the electric types, may only give off up to 10,000 BTU's.
Atmospheric conditions and placement of the heater will generally determine how much available warmth there is, regardless of any BTU rating. For example, if you’re sitting on a patio in windy weather, even at a minimal of 5 miles per hour, the radiant area that is heated will be halved.
In other words, if your heater is rated to heat up a surrounding area out to 20 feet, it may only make usable heat at up to 10 feet in this scenario. In a 10 or 15 mile per hour wind, unless you are sitting or standing directly under the heater, or it is next to you on a table, there will be little to no heating benefit. Rain, snow and ambient temperature must also be taken into consideration and these factors will also limit how much heat you feel.
However, in optimum conditions when there’s no wind and the temperature is in the low 60's to mid 50's, a patio heater will live up to the manufacturers specifications and raise the temperature by as much as 20 degrees or more over the stated performance area.
Patio Heater Types
Free-Standing Floor Models
These are the most common types available, essentially looking like a thick pole with an umbrella top hat. They all have a safety shut off switch if they were to tip over, wheels for portability, and these models come in both electric and gas models. The gas models have the highest BTU output so they have the capability to heat up a larger area. Also, gas models overall are far more energy efficient than electric models, but their downside is you'll always need to refill the propane tank when it runs out.
Free-Standing Table Models
These are essentially miniature versions of their floor standing cousins, available as either gas or electrically powered units. They sit on top of a patio table and are capable of warming only the people sitting around the unit. The gas models are the most economical heaters to use, and they are the least affected by adverse environmental conditions.
Mounted Models
Virtually all of these types are electrically powered and depending upon what design fits your needs, they can be mounted beneath eaves, beneath a patio umbrella, hung like a swag lamp, or attached to the ceiling. They use infrared heat that effectively heats you and not the surrounding air. These are the most expensive patio heaters to run, with some consuming up to 6000 watts of power each time they’re turned on.
Fuel
Propane
The most common fuel type is propane. Large free standing units have their own propane tank storage in their base, but they can also be hooked into your regular home-fed propane tank. Smaller table top units use propane cylinders for their fuel which can be found at department stores, hardware stores, and at most specialty home/garden shops. Propane models are the most cost effective units to run, and they have the highest BTU models available.
Electricity
Most of these types can be used both indoors and outdoors, and the design varies from the traditional free-standing umbrella style, to long rectangular under-eave models, hanging lamp types, and flower petal designs that fit beneath a patio umbrella. Although they’re the most expensive types to run (with models consuming between 1500 and 6000 watts of power) they can be placed in spaces a gas fueled unit can't. Plus, you'll never have to worry about running out of fuel unless you don't pay the exorbitant electric bill you'll get while running them.
Natural Gas
Natural gas units are directly attached to your home gas piping system. In this scenario, they’re generally permanently placed fixtures. These are the most economical units to operate, but virtually all of them will be essentially free-standing floor units.
Features
Thermostatically Controlled
Every unit will have some type of thermostatic control. The simplest types will be a “low” and “high” setting on a rotary knob. The more advanced types will have an actual temperature range that you can set and forget. Mounted models can be designed to have a wall mounted thermostat while free-standing and table models will have the control on their body.
Piezo Electric Starter
Virtually every modern gas fueled patio heater will have a piezo electric starter. Just turn on the gas and hit the red “start” button. You'll have instant flame lighting at your finger tips. Higher end models that are thermostatically controlled, will automatically turn off when the set temperature is reached, and restart when the temp drops below the setting.
Features
Adjustable Reflector Top
Many of the tops on umbrella style heaters can be tilted to concentrate the heat towards a certain area. This feature can come in handy if there’s a concentration of people in one section of the patio. You can maximize the heating capability in that one particular area so there’s no wasted heat directed at an empty area.
Visual Aesthetics
Aesthetics can be an important aspect of patio heaters. Basic models look like towers and have a stainless steel or powder coated colored exterior. But higher end models can have glass centers, so you can watch the flames shoot upwards, with others resembling pyramids or lanterns, as well as a host of other designs that will mesh well with the décor of your patio.
What's Best for You
Function and effectiveness will be your main reason for getting a patio heater, while cost to run it may also come into play.
Outdoor Patios
These are the hardest areas to heat, since they are exposed to the elements. A basic rule of thumb is to get the largest gas powered BTU unit that you can afford. Most free-standing gas heaters are rated to heat up to 20 feet. If your patio is 40 feet long, you'll need at least 1 of these heaters to effectively bring up the temperature within that area, and in optimum conditions, 1 will do the job. Ideally, 3 units would be perfect: 1 at each corner and 1 in the middle. That would effectively cover both the length and width of your patio. However, if there is even so much as a moderate wind, your patio heater effectiveness will drop considerably.
Outdoor Tables
If you just want to heat up the area around an outdoor table, a single table top patio heater will do the trick. You'll maximize heat potential if you have an umbrella that will capture the rising heat. To that end, an under umbrella mounted electric heater may also work for you. They funnel heat downwards to anyone sitting around the table while capturing heat that rises beneath the umbrella.
Semi-Enclosed Patios
These spaces are the easiest places for a patio heater to heat. The ceiling captures rising heat, and the shelter of the semi-enclosed patio design lends itself to optimum heating conditions. Mounted electrical heaters work equally well in this scenario, but gas powered units would still be the most economical to use. Semi-enclosed patios also are the best places for thermostatically controlled units, since the heat retention of this design means the heater does not have to run continuously.
Indoor Patios
Your only real option here is to go electric since you can’t run a gas powered unit inside of a confined space due to the fumes emitted when they burn. Thermostatically electric units are best here, and if you're only interested in heating up the area around a table, a hanging electric heater would be ideal for that purpose.