Comparing Flued vs Unflued Gas Heaters – Review & Prices

Comparing Flued vs Unflued Gas Heaters – Review & Prices

Australians looking to buy a gas heating will find that the available gas heaters for sale are broadly grouped as either unflued gas heaters (portable gas heaters) or flued gas heaters for the home.

Both are available in either natural gas or LPG models.

What is the difference between flued vs unflued gas heaters and which one should you buy?

Here is a review of the pros and cons for you to consider when you decide on which type of heater is right for you:

Unflued Gas Heaters

Unflued gas heaters are typically much more energy efficient than flued models and have higher Energy Star ratings.

Unflued gas heaters are also less expensive, as they do without any flue kit and the installation is much faster.

Unflued gas heaters have neither a flue nor a chimney.

As a result, they release some combustion gases and water vapour directly into the home.

The maximum levels released by unflued gas heaters are specified by government safety regulations.

Flued Gas Heaters – Rinnai Flued Gas Heaters – Flued LPG Gas Heaters – Gas Fixed Flued Heater

Flued gas heaters have a flue pipe that directs combustion gases out of your home through a flue or chimney.

This means that there are no combustion gases and water vapour emitted inside your home.

Someflued heaters have a powered flue, with an electric fan driving the gases out of the flue.

Flued heaters tend to cost more than unflued gas heaters because of the extra flue hardware and installation required.

Learn more about the details involved with both types of heaters…

Indoor Emissions – Are Unflued Gas Heaters Safe (Natural Gas or LPG)

The term “flued” refers to the fact that the combustion gases generated when the gas is burnt are directed out of your home by means of a fixed flue pipe through the wall or ceiling.

As a result, there are no emissions in your home.

The accompanying diagram shows an installation example of a flue through a wall

Care should be taken when using unflued gas heaters if the family includes very young, unborn, elderly or individuals with some medical conditions, as they may be more sensitive to the emissions.

However, for the majority of people, unflued gas heaters are quite safe when you follow all of the manufacturer’s safety instructions, including providing adequate ventilation.

Energy Efficiency & Operating Costs of Flued vs Unflued Gas Heaters

Unflued gas heaters are more efficient than flued gas heaters because some of the heat is lost through the flue.

The typical Star Ratings for unflued gas heaters are from 5.8 to 5.9 Stars, meaning that they are about 90% efficient in converting the gas to usable heat.

Flued heaters can have a broad range of performance, with Star Ratings from 1.0 to 4.8 Stars.

This equates to 61% to 84% efficiency levels.

This means is that you could save as much as 32% of the cost of heating by choosing an unflued heater compared with some flued heaters.

Portability of Unflued Gas Heaters

Unflued gas heaters can be moved where needed, from one room to another, as long as each room has a gas bayonet connection.

This is why they are commonly referred to as Portable Heaters.

The heater plugs into the bayonet connection via a gas hose.

This also allows you to rotate the direction of the heater, to aim the heat at or away from a particular part of the room.

On the other hand, flued heaters are fixed in place by the gas connection and flue.

Gas Heaters & Moving Home

Portable gas heaters (portable LPG gas heaters) are much easier to take with you when you move than flued gas heaters (flued LPG gas heaters).

You simply disconnect it from the gas heater bayonet connection and go.

Moving flued gas heaters (gas fixed flued heater) requires a gas fitter to uninstall the unit and reinstall it for the new home.

There is also the issue of the flue hole in the wall or ceiling if you remove the gas fixed flued heater.

In addition, most home buyers would consider flued gas heaters to be a built-in appliance and expect it to remain with the house.

Comparison of Flued Gas Heaters vs Portable Gas Heaters Purchase Cost

Flued Gas Heaters for the home (gas fixed flued heater) are more expensive to purchase than portable gas heaters (unflued gas heaters).

For example, when comparing comparably sized flued gas heaters (flued LPG gas heaters) and portable gas heaters (unflued gas heaters) from the same manufacturer (Rinnai gas heater), the gas fixed flued heater are 44% to 57% more expensive than the portable gas heaters.

Depending on the model and installation situation, you may also need to purchase an accessory flue kit when you install  gas fixed flued heater.

Installation Cost of Portable Gas Heaters vs Flued Gas Heaters for the Home

If you already have a gas heater bayonet connection in your home, there is no cost to install a portable gas heaters (portable LPG gas heaters).

So, while not prohibitively expensive, it does cost more to install flued gas heaters (gas fixed flued heater) for the home than portable gas heaters (unflued gas heaters).

Even if you need to add a gas heater bayonet connection, the installation costs for portable gas heaters (portable LPG gas heaters) would be modest.

Installation of flued gas heaters (flued LPG gas heaters) in your home requires the services of a gas fitter in all circumstances.

There is also the cost of installing the  gas fixed flued heater flue kit through the wall or ceiling.

What Size Gas Heater Do I Need?

What to Consider

If you buy too small a heater, it will not be able to adequately heat the intended area.

Selecting a heater that is too large will cost you extra money and oversizing can be unsafe.

A number of things need to be considered when determining your heater sizing:

♦  The volume of the area to be heated including consideration of ceiling height.

♦  The climate zone that you live in.

♦  The physical features of your home including wall & ceiling insulation, window coverings and carpeting.

♦  The kW output of the gas heater, not to be confused with the gas Mj input.

Heating Area Volume & Climate Zone

The required kW output required is primarily dependent upon the area to be heater and the climate zone in which you live.

The following rough guide assumes your ceilings are no higher than 2.4M:

Very Cold Zone: 1kW output required for each 8.5m²

Cold Zone: 1 kW output required for each 10m²

Cool Zone: 1kW output required for each 13 m²

Mild Zone: 1kW output required for each 16m²

Adjustment Factors

The indicated heating areas would be adjusted down by 5% for each of the following conditions: house built on pillars (non-slab), no carpets on floors, no drapes on windows or a ceiling height exceeding 2.4m.

Deduct an additional 10% if the area does not have ceiling insulation.

Please note that this is only a guide and individual home designs and situations may vary.

Gas Heater Sizing Example #1:

You live in the Cold Zone and you want to heat an area 5m X 10m, which equals 50m².
Because 1kW will heat 10m², you should need a heater with a 5kW output.

Gas Heater Sizing Example #2:

Same as the previous example but in this case your ceilings are over 2.4m and you have wood flooring instead of carpeting.

You would need to deduct 5% for each of these two items.

So, instead of 1 kW heating 10m², it would heat 9m² (10% total reduction).

This means you would need a heater with 5.6 kW of output (50 ÷ 9).

Use kW not MJ

Megajoules per Hour (MJ/hr) ratings on appliances actually indicate the gas consumption of the appliance, not the heat output.

It is often expressed as just MJ.

Kilowatt (kW) is how gas heater output is measured.

Energy Efficiency Matters – Star Ratings

So, remember to use kW as a comparison and not MJ.

The efficiency of the heater, in converting gas energy to heat, is a key factor.

For example, a 25MJ heater with a 5.8 Star rating has an output of 6.2kW.

A 25MJ heater with a 2.8 Star rating only has an output of 5.0kW.

As a result, in a Cold Zone climate, they would heat 62m² and 50m², respectively.

This means that the 5.8 Star heater will heat an area 24% larger while using the same amount of gas.

Please refer to the manufacturers’ specifications to determine the exact kW output for each heater you are considering.

Minimum Room Sizing

Some States specifiy the minimum room sizing (volume of room in M³)  and minimum ventilation requirements for unflued heaters.

Minimum room sizing also varies between thermostatically controlled and manually controlled heaters.

Portable heaters should not be used in bedrooms, bathrooms or hallways.

All installations must comply with Australian Standard AS5601 – Gas Installations.

Your gas fitter will be able to guide you on many of these points.

Manufacturer Sizing Charts

To make it even easier, most manufacturers have sizing charts, for their heaters, based on climate zone maps.

Take the time to measure the area you wish to heat and use these charts and maps to get the correctly sized heater.

It is always wise to follow the manufacturers’ advice.