The CHOICE Expert Rating  is made up of heating (70%), ease of use (20%) and standby power score (10%).

We score the heaters on how quickly and evenly they heat up the test room. For models with an additional electric heating element, the score is based on using the electric heating element together with gas heating. We also test these models with the electric element off (i.e. gas heating only), and find they perform nearly as well, with scores only a few points lower.

The testers assess how easy the controls are to use, how clearly the controls are marked and how easy the manual is to follow.

Most gas heaters need to be plugged into a power point as they use electricity for ignition and for their controls, so they use power even in standby mode. The less they use, the better their standby power score. Some have batteries that mean they don't need to plug in for ignition.

This is the measured gas that the gas heater consumes.

We recommend gas heaters that score 70% or more overall and 75% for their heating score. Note that models in different size ranges can’t be directly compared because heaters with different capacities are designed for different room sizes, so filter by room size or heater capacity (13–15 MJ/h, 18–21 MJ/h or 25 MJ/h) to find the right models for your needs.

This column shows which products have been discontinued and which are still available in shops. 'Tested models' can still be found in shops. 'Discontinued models' are models we tested but which have since been discontinued; they might still be found second-hand or in discount stores.

Recommended or typical retail price. You can often get a better price by shopping around.

This is the amount it costs to run the heater based on full blast (highest setting possible) at 4c/MJh.

Most heaters declare the heat output in Kilowatt Hours (kWh). Roughly speaking, 1 kW = 10 square metres of room heating. So if you have a 3 x 4 m room (12 sqm), you'll need a has heater with at least 1.2 kW heating output (12sqm / 10).

Based on the kW heat output. Room sizes are classified as follows: Small = 29 - 52sqm. Medium = 64 - 90sqm. Large = 65 - 113sqm. There are discrepancies in sizing due to the self regulation of the industry.

Note that models in different size ranges can’t be directly compared because heaters with different capacities are designed for different room sizes. Compare each heater against others in the same gas consumption range: small or 11–15 MJ/h, medium or 18–21 MJ/h and large or 25 MJ/h +.

Some models have a basic range of settings such as low, medium and high, or a simple slider ranging from low to high. Others have a thermostat allowing a finer range of specific room temperature settings.

The AS4553 Efficiency Star Rating is based on an industry-designed rating scale from 1 to 6 stars. Most models rate very highly in this scheme so it's not as useful as star ratings based on Australian standards, such as those applied to fridges and air conditioners.

Our results table shows the maximum recommended room floor size (assuming a standard ceiling height of 2.4m) in a cool climate. But as well as room size, consider the climate where you live. A model might heat 57m² in a cold climate but 87m² in a mild climate. 

Unflued gas heaters must have a stated minimum room volume to ensure they aren't used in a room that's too small, where their waste gas output might be at too high a level. SA, Victoria and WA have further restrictions on the use of this heater type — check with a gas plumber or retailer. We've converted the minimum volume to a minimum floor area in square metres, assuming standard ceiling height of 2.4m.

Convection (or convector) heaters work by heating the air and letting it circulate up and around through the room (usually pushed by a fan). Radiant-convection heaters radiate heat from an element at the front, so they're best for personal heating (i.e. sitting in front of the heater), but they also produce some heat by convection.

Where the manufacturer claims the heater was made.

Useful for switching the heater on at certain times (to pre-warm the house before evening, for instance) and to switch it off again automatically.

Important safety feature to prevent curious youngsters fiddling with the controls.

If the flame goes out, does the heater claim to switch off after a certain amount of time?

The ODS pilot claims to shut off the heater if the normal air oxygen content in the room is reduced below a safe level.

Does the gas heater have a warning that tells you when the filter needs to be cleaned?

A range of fan speeds is useful. Some have two manual settings (low and high) while others have an automatic fan that adjusts its speed depending on the room temperature and the thermostat setting.