Shop Jetboil Jetboil Joule. The Joule is perfect for backpacking groups and alpinists. It offers consistent heat output down to 10°F/-12°C thanks to a proprietary regulator technology. It’s inverted fuel can and liquid feed regulator provide the performance of a liquid/multi fuel stove but with the ease of use and versatility of a canister system. Setup and reliability are improved over liquid/multi fuel stoves which require significant assembly and priming before use.