Your heating options
 
Portable oil-filled column heater or convection heater

Their heating capacity is limited to 2.4 kW, so they're suitable for areas like bedrooms and small to medium living areas. Their effectiveness will depend on the climate and how well insulated the room is.

If they're not fan-assisted, they heat the room quite slowly. With or without a fan, they're not fast space heaters and so are better for rooms that need heating over long periods. Look for models with a thermostat and a timer.

For more see our Electric column heaters test.

Off-peak storage heater

This type of heater uses cheap off-peak electricity during the night to heat up a storage material (usually bricks). This heat is then released into the room during the day. Storage heaters are less flexible than other types, and you may need an extra heater in the evening if they run low on stored heat.
Reverse-cycle air conditioner

These use electricity to 'pump' heat from one place to another. Even on a cold day, the outside air contains heat that can be pumped inside.

Air conditioners are rated according to their heat output, which is higher than their electricity input, giving them an efficiency of up to 250%. However, their efficiency declines the colder it gets outside.

Room air conditioners come as wall or window units and as split systems, which are much quieter because the working part (compressor) is installed outside the house. Larger models may require a separate electric circuit.

For more see our Reverse-cycle air conditioners (6.8 kW) test.
Gas

Unflued radiant and/or convection heater

Unflued heaters vent their combustion gases (carbon monoxide, nitrogen dioxide, water vapour) into the room. In Victoria you're not allowed to use unflued natural gas heaters for that reason (unflued liquified petroleum gas (LPG) heaters can be used under certain conditions). NSW, Queensland, SA and WA also restrict the use of unflued natural gas and LPG heaters.

We recommend you ensure good ventilation when using one -- particularly because of the water vapour, which could otherwise cause problems with condensation. For safety reasons, unflued gas heaters aren't suitable for bedrooms and bathrooms.

You can get them with a heating capacity from around 8 MJ to over 25 MJ per hour (depending on the size of your room), and they use almost all the heat that's contained in the gas (up to 90% efficiency), though the necessary ventilation can cause additional heat loss. They're usually portable (which is handy if you have a gas connection in several rooms), and easier and cheaper to install than flued heaters.
Flued heater

Flued heaters come as console (standing against a wall), inbuilt or log-fire-imitation models. They cost more than unflued models because of the flue installation. But as the combustion gases are vented outside, you won't have the problems mentioned for unflued heaters.

Flued heaters are particularly suitable for living areas and bedrooms. However, they're less efficient than unflued heaters (up to 75% efficiency), because part of the heat is lost with the gases through the flue.
Solid fuels

The key to efficient solid-fuel burning is to control the air supply, so that the fuel doesn't burn too fast and heat isn't lost.
Open fire

Open fires may be romantic and nice to look at, but they only produce very localised heat and they're very inefficient: around 85% of the energy is lost straight up the chimney. In most places you'd need an additional heater.
Non-airtight stove

Non-airtight stoves, such as pot-belly stoves, get very hot and supply mainly radiant heat. You can't accurately control the air supply to the fire.

They have an efficiency of around 30%, and aren't suitable for heating large areas over long periods of time. However, they're relatively cheap, so could be considered for areas that only have to be heated occasionally.
Slow combustion

Modern slow-combustion stoves have an airtight firebox, and air inlet controls to regulate the amount of air supplied to the combustion chamber. They're up to 70% efficient and must comply with Australian standard requirements regarding their flue gas emissions.

Manufacturers of slow-combustion heaters usually state the size of the area you can heat with any particular model. However, the heat output depends on various factors, such as which fuel you use, how damp it is and how you load and maintain the heater.

Small, medium and large slow-combustion heaters are available. Small models (with a heat output of up to 15 kW) are the most commonly used for room heating, with radiant models (without a fan) being able to heat areas of up to 90 square metres, and convection models (with a fan) heating up to 130 square metres.