Elgas LPG Gas Blog

Never Run Out of Hot Water or LPG - 8 Great Tips

We know that there is nothing more inconvenient than being out of home LPG gas. 
Here are a eight handy tips, if you are a gas bottle exchange customer, to help you stay in gas…

Eight Tips for Never Running Out

1. Always order gas as soon as the first bottle runs out. 

Don't wait until the gas bottles are both empty or near empty. 

Follow this advice and you are virtually assured to never run out of gas.

2. Remember to order sooner, rather than later, during the busy winter season. Order your gas online

You can even order online. 

Just look for the Blue Button

3. Remember to check your gas bottles more often in cold weather, especially if you use a gas heater or gas log fire. 

Even your water heater has to work harder in cold weather, as the incoming water is colder.

4. Having additional house guests can also increase your usage if you have gas hot water. 

Running out of hot waterRemember to check more often so both you and your guests avoid cold showers!

5. If you only have one gas bottle attached to your home, you may wish to consider adding a second gas bottle. 

Unless you are on automatic tanker delivery, you will either run out or have to call for a gas bottle exchange before using up all of your gas. 

These are both situations you would surely like to avoid. 

A second bottle solves the problem and is particularly wise if you use your gas for hot water and/or heating.

6. Make sure we have your Mobile Number so you receive Gas Check Alerts™ by Text (SMS). 

These are sent automatically, by our computer, based on your past gas usage. With Gas Check Alerts , you will never forget to check your gas bottles again.

7. Remember to increase how often you check your gas bottles if you install additional  gas appliances.

8. Also, be certain to tell us if you install additional appliances, especially if you are on automatic tanker delivery, so we can adjust your delivery schedule.

Follow these tips and you should enjoy using of your gas appliances without interruption.

Never Run Out of Hot Water Again

Gas Continuous Flow Hot Water Systems

Sometimes referred to as 'continuous flow', ‘instantaneous’ or ‘tankless’, these units heat the water as you need it.
Tankless continuous flow systems provide hot water on demand whenever you turn on the tap.
These units only heat the water as it passes through so there is no storage tank.  
This also means you never run out of hot water. 
With tankless systems, you only need to heat the water to 50°C, as the prevention of bacterial growth is NOT an issue with tankless units, as it is with all of the other alternatives that have tanks.
While the running costs are not quite as low as solar and heat pump units, the upfront costs are much lower. 
Greenhouse gas emissions are also much lower than electric storage.  
Available in both natural gas and LPG versions, these units are very energy efficient, with 5-Star or better ratings.

Learn How Long 45kg Gas Bottles Last

Knowing how long a bottle will last helps to anticipate ordering gas and never running out.

“How long will my gas bottles last?” is one of the most common questions we hear. 

There is no single answer to this question and a bit of explanation is required to get to the answer for your specific situation. 

Figuring it out is actually easy.

Important Reference Information

45kg gas bottlesTo get started, here are some numbers you will need to know for your reference:

Energy equivalent conversion: 

1kW/hour = 3.6MJ

1kg of LPG = 1.96 litres of LPG (propane)

LPG contains approximately 25MJ per litre

A 45kg gas bottle contains about 88 litres of LPG or 2200MJ of energy

Efficiency Matters

The MJ inputs and kW outputs are directly related but are affected by the efficiency of the appliance. 

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

Now, if you do the maths, dividing 25MJ ÷ 3.6MJ, you would expect that the output to be 6.94kW, not 6.2kW. 

The difference is that, at 5.8 Stars, the heater is 89.3% efficient.  

No gas appliance is 100% efficient, which is why we have the Star rating system to judge the relative performance of different models.

Examples of How Long a 45kg Gas Bottle Will Last

So, now that you have the background information, we can get back to answering the original question. 

The best way to do this is with examples:

Heater Example:

Gas Heater

A 15MJ 5.8 Star gas heater running at its maximum setting will last approximately 147 hours on a 45kg gas bottle. 

We know this because the gas bottle contains 2200MJ. 

The math is as follows: 2200MJ ÷ 15MJ = 147 hours. 

However, this same heater, when set on low, consumes 6.0MJ. 

So, if you operate it on low only, it will last 367 hours (2200MJ ÷ 6MJ = 367 hours). 

As most people would vary the settings, depending on the temperature, the gas bottle will last some duration between 147 and 367 hours. 

So, if you use your heater for four hours every evening, you would expect your gas bottle to last anywhere from 37 to 92 days.

Hot Water Example:

Gas Hot Water

A 16L/min 130MJ 5.0 Star continuous flow hot water heater running at full capacity will last for 16.9 hours of actual run time. 

This equates to about 204 five minute showers. 

However, the water heater can run at a flow rate of as little as 3.5L/min. 

When running slower, the unit will self-modulate and consume less gas. 

This would increase the run time by roughly 4X or to about 68 hours. 

This equates to around 816 five minute showers. 

Assuming you use hot water for other things, as well, totalling 20 minutes per day at maximum, your gas bottle would last about 50 days.

Cooktop Example:

Cooktop burners are an even greater challenge to calculate. 

The burners on a particular cooktop could vary from 5MJ for the smallest burner to 9MJ for a medium burner, 12MJ for a large burner and 15MJ for a wok burner.  

Add to this the fact that each can be run at less than maximum and you can see the maths challenge. 

If you use the medium 9MJ burner as the average, you get 244 hours of cook time. 

Not surprisingly, many cooking customers report that a single bottle can last more than a year.

What if you have multiple appliances?

Now the math gets really challenging! 

You really can’t add the MJ ratings of all of the appliances together, as they would rarely be used all at the same time and for the same duration.

The easiest method of calculating would be to estimate how long you would use each appliance per day and total their daily consumption. 

Using the previous appliance examples:

  1. You use your hot water for 20 minutes per day on maximum.  This equals 43MJ of consumption.

  2. You use your heater, on maximum, for 4 hours every evening.  This equals 60MJ of consumption.

  3. You cook, using one medium 9MJ burner, on maximum, for 45 minutes per day.  This equals 7MJ of consumption.

  4. Adding these all together, you are using 110MJ per day.  Based on this, you would expect a 45kg gas bottle to last for approximately 20 days. (2200MJ ÷ 110MJ = 20)

Quick 45kg Reference Chart

For those who can't be bothered with the maths, here is a quick reference chart with examples:

How long a 45kg LPG gas bottle-cylinder will last - Chart

Compare gas hot water systems prices


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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.