What Size Gas Heater Do I Need?
The size gas heater you need for a small room (29m³ - 42m³) has a heat output of 2.9 – 4.2kW. A medium room (42m³ – 66m³) needs a gas heater size with 4.3 – 6.6kW. Large rooms (66m³ - 82m³) need a gas heater size with a heat output of 6.7 to 8.2kW.
Do not go by MJ ratings, as heat output can vary greatly based on gas heater efficiency. Using kW is the net heat output that you are looking for.
These gas heater sizes are all approximations and your situation may be different based on climate, insulation, ceiling height, the number of fenestrations, window coverings, drafts, floor coverings and sub-flooring. Rinnai has a very good gas heater sizing calculator that takes many of these variables into consideration.
It is important to get the right size gas heater for your home.
You want to select the ‘Goldilocks’ heater that is just right for your gas heating needs.
Gas heating is the heating of a room or outdoor area using a gas space heater fuelled by natural gas, LPG (propane or butane) or biogas. Indoor gas heater types include unflued portable gas heaters, flued gas heaters, radiant gas heaters, convector gas heaters, radiant-convectors, and gas fireplaces.
A gas heater is a space heater used for room heating or outdoor area heating fuelled by natural gas (including CNG and LNG) or LPG (propane, butane or a mixture of the two). The two general types of home gas heaters are flued gas heaters (vented) and unflued gas heaters (unvented).
What to Consider
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
Very Cold Zone: 1kW output required for each 8.5m²
Gas Heater Sizing Example #1:
Gas Heater Sizing Example #2:
Use kW not MJ
Energy Efficiency Matters - Star Ratings
Minimum Room Sizing
Manufacturer Sizing Charts
Compare Indoor Gas Heater Prices
A Megajoule or MJ Probably Isn't What You Think
What is a megajoule and why does it matter when I buy a gas heater?
What size gas heater should I buy?
How do I compare heater prices?
Many people think they know but you might be surprised by the real answer.
A MJ is NOT This...
I recently watched a product video produced by a major Australian retailer.
In it, a “Product Expert” reviews a Rinnai gas heater.
He did a fair job of explaining the features, even if you could get the same information from the Rinnai gas heater web site or product brochure.
The problem was that the presenter lost me in the second sentence when he said: “That’s 13MJ of heat.”
He also makes a similar statement in at least one other video.
To quote the popular Gen Y meme… EPIC FAIL!
Sorry, but there is nothing worse than an “expert” giving out bad advice.
Please let me explain…
Gas Consumption = 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.
On the other hand, heat output must also take into account the relative energy efficiency ratings of the models being compared.
How is it pronounced? Say it as if it were spelled "mega jewel" or "mega jewels", not "mega jowl".
Heat Output = kW
Kilowatt (kW) is how gas heater output is measured. 3.6 MJ of input equals 1kW of output at 100% efficiency.
However, no gas appliance is 100% efficient.
That is why we have Star Ratings, so we can compare relative efficiency between models.
Appliance output is often expressed as just kW.
Energy Efficiency - Star Ratings
Star ratings were developed to provide consumers with an easy way of comparing the energy efficiency of different models.
All States now require both LPG and Natural Gas heaters to be tested and certified, under AS4553, by independent testing organisations, such as the AGA and SAI Global.
The Star Rating is based on net heater efficiency.
Net heater efficiency is calculated on the basis of a combination of efficiency measures and takes into account all gas and electrical inputs.
It basically compares the amount of raw energy input consumed by the heater in comparison to the heat energy output provided.
This is calculated as a percentage and then translated into the corresponding Star Rating.
Here are some special gas heater deals:
Comments, questions or feedback?
The information in this article is derived from various sources and is believed to be correct at the time of publication. However, the information may not be error free and may not be applicable in all circumstances.