Patio Heater Gas Bottle Runtime Calculator
Running out of gas mid-evening is a common frustration with outdoor heating, and buying the wrong bottle size means either wasted spend or an unplanned trip to swap it over. Enter your heater's output and bottle size below to see roughly how long it will keep running.
Work out how long your gas bottle will last
Enter your patio heater's heat output and your gas bottle size.
A 13kg bottle running a 13kW heater at full output should last approximately:
13.8 hours
If your heater has a lower setting, running it below full output will stretch this considerably further — this figure assumes continuous use at maximum heat.
Recommended products
A few well-reviewed patio heaters to consider.
- Gas
£89.99
Pros
- Pyramid tower gives 360° ambient flame light and warmth
- Ignition lighter starts the flame quickly and safely
- Charcoal grey finish blends into most gardens
Cons
- Uses a standard gas bottle not included
- Larger footprint than a slim column heater
- 13kW
£139.99
Pros
- Classic mushroom design throws heat over a wide radius
- Brushed stainless steel resists rust and corrosion
- Piezo ignition and tilt safety shut-off included
Cons
- Heavy — needs two people to assemble
- Gas bottle not included
- 2.5kW
£219.00
Pros
- No gas bottles to buy or store
- IP55 weatherproof for year-round outdoor use
- Remote control with 4 heat levels and carbon fibre glow
Cons
- Needs a nearby outdoor power socket
- Wall or ceiling fixing required
Frequently asked questions
How long does a 13kg gas bottle last on a patio heater?
A standard 13kg propane bottle typically runs a 13kW mushroom-style patio heater for around 13-14 hours at full output, though this varies with the exact heater rating and outdoor conditions.
Does turning the heat down make a gas bottle last longer?
Yes — most patio heaters let you run at a lower setting than their maximum rating, and doing so uses gas more slowly, so a bottle that lasts under 14 hours at full power could last considerably longer on a medium setting.
Why does my patio heater seem to use gas faster in cold or windy weather?
Wind carries heat away before it warms anyone nearby, so people often turn the heater up or position it more exposed to compensate, which increases gas consumption even though the heater itself isn't running any less efficiently.
Is propane or butane better for a patio heater in the UK?
Propane is generally the better choice for UK outdoor use because it continues to vaporise properly in cold temperatures, whereas butane struggles to perform once the weather turns cold, which is exactly when a patio heater is needed most.
How this calculator works
The calculator uses the heater's BTU (British Thermal Units) output – a measure of its heating power – as the primary factor. We then apply a ‘loss factor’ to account for heat lost to the surrounding air, which is influenced by temperature and wind speed. A colder ambient temperature and stronger winds will significantly reduce the heater’s efficiency, meaning a shorter runtime.
The calculator multiplies the heater's BTU output by a calculated 'effective hours' value based on your chosen temperature (ranging from 5°C to 20°C) and wind speed (from still to moderate breeze). This provides an estimated number of hours the gas bottle will effectively heat your patio. It’s important to note that this is an estimate; actual runtime can vary depending on precise conditions.
Gas Bottle Sizes and BTU Outputs (UK)
| Gas Bottle Size | Diameter (cm) | Height (cm) | Approximate BTU Output |
|---|---|---|---|
| 1/3 kg Bottle | 30 | 80 | 10,000 - 12,000 |
| 2/3 kg Bottle | 45 | 110 | 16,000 - 19,000 |
| 1kg Bottle | 60 | 140 | 24,000 - 28,000 |
| 2kg Bottle | 90 | 180 | 36,000 - 42,000 |
Worked example: 2kg Bottle Runtime
Let’s calculate the estimated runtime of a 2kg gas bottle connected to a patio heater with an output of 36,000 BTU. We'll assume an ambient temperature of 10°C and a moderate breeze (wind speed factor of 0.7 – representing a slight wind). The calculator estimates that at 10°C and a moderate breeze, a heater like this will have an effective runtime of approximately 6 hours.
This means the gas bottle should provide around 6 hours of heating under these conditions. However, if the temperature drops to 5°C or you experience a stronger wind (wind speed factor of 1.0), the estimated runtime would decrease accordingly – potentially down to 4.5 - 5 hours. Remember that prices for gas bottles vary depending on retailer and brand; a typical 2kg bottle currently costs around £35-£55.
More questions answered
What units does the calculator use?
The calculator uses hours as the primary unit for runtime. BTU (British Thermal Units) are used to measure heater output, and wind speed is expressed as a factor influencing heat loss. Temperature is in Celsius.
How accurate is this calculator's estimate?
This calculator provides an *estimated* runtime based on averages. Actual runtime will vary due to factors like wind speed, ambient temperature, heater efficiency, and the specific model of your patio heater. It’s a useful guideline, but don’t rely on it as the absolute truth.
What does the ‘wind speed factor’ represent?
The wind speed factor is an adjustable value that accounts for heat loss due to wind chill. A factor of 1.0 represents a strong breeze, while 0.5 indicates little to no wind. You can adjust this based on your local conditions.
Can I use this calculator if my patio heater has a different BTU output?
Yes, you can! Simply enter the BTU output of your specific patio heater into the calculator's input field. However, ensure you are using accurate BTU figures provided by the manufacturer.
What temperature should I enter for the ambient temperature?
Enter the actual ambient temperature – the temperature of the air around your patio. This is usually measured in Celsius. Consider that colder temperatures will significantly reduce the heater’s effectiveness.
Does the calculator account for different types of gas patios heaters?
The calculator provides a general estimate and doesn't differentiate between specific types of gas patio heaters (e.g., butane, propane). However, the underlying principles – BTU output and heat loss – apply to all gas patio heaters.
What if I’m using my heater in very wet conditions?
High humidity can also affect a gas patio heater's performance. While this calculator doesn't directly account for humidity, extremely high humidity will reduce the heater's efficiency, shortening runtime. Consider adjusting your wind speed factor upwards slightly.
How do I find the BTU output of my patio heater?
The BTU output is usually listed on the product packaging or in the manufacturer’s specifications online. Check the product details on Amazon UK or the heater's manual.
Should I always buy a larger gas bottle than I think I need?
It's generally advisable to purchase a slightly larger gas bottle than you initially estimate, particularly if you plan to use your patio heater for extended periods. This provides a buffer against unexpected changes in temperature or wind.
Can this calculator help me choose the right sized patio heater?
While this calculator focuses on runtime, using it alongside other factors like patio size and desired heat output can certainly inform your choice of patio heater. Consider the heater’s BTU rating carefully to ensure it's suitable for your space.