Looks like Jetboil plans to drop the Helios from their group cooking system line next spring and replace it with the new Joule. The Joule improves upon the inverted canister design concept of the Helios to offer a more streamlined package (no external cables), ease of use compared to a liquid fuel stove, fast boiling times, and exceptional cold weather performance.
The Joule gives you liquid fuel performance in a more user friendly canister stove. Similar to the Helios, the Joule uses an inverted canister design with a new liquid feed regulator for better liquid fuel performance. Ribs inside the regulator vaporize a tiny amount of fuel in order to ignite the stove. This means no priming is required as with standard liquid fuel stoves. The burner head is also 25% larger than on other Jetboil stoves and convex versus concave shaped, enabling it to pump out more heat.
When the propane/iso-butane mix is stored under pressure in the Jetboil fuel canisters, it turns into a liquid. When you open the stove valve, some of the mixture vaporizes and turns into gas. There are two different ways to get propane from a fuel canister, vapor withdrawal or liquid withdrawal.
Most personal cooking systems use vapor withdrawal, simply grabbing the vaporized gas from the top of the canister. As propane vapor is used, the pressure in the canister decreases, which in turn causes the liquid propane to vaporize, replacing the vapors which have been used. This method works great when the air temperature is generally 40°F-50°F or warmer.
With the new inverted canister design, Jetboil can directly grab liquid fuel when the valve is open. This method works best as the air temperature decreases, especially in lower BTU applications such as camping stoves (versus your outdoor grill). Boil times will be consistent down to 15°F and Jetboil says even a steady performance at -10°F is possible.
One thing people complained about with other Jetboil stoves is their inability to simmer properly. The Joule can easily simmer, as the stove is regulating on a liquid versus a vapor level, so you won't run into the problem of it shutting off at low flame levels.
As your average backpacker, unlike an alpinist, does not care about sub-zero temperature performance, Jetboil was sure to focus on boiling time with the new Joule. Pumping out 10K BTU of heat, the Joule will boil 1/2L water in about 1 min 20 secs or 1L in 2 min 40 secs.
The Joule features a 2.5L pot with insulated FluxRing at the base and an integrated handle that folds for storage. The lid is see-through and includes a strainer for all your one pot gourmet meals. The stand and fuel canister pack up nicely into the pot when you are ready to throw it back into your pack. Jetboil will also offer a new Frypan with FluxRing technology for those looking for a little more cooking variety.
The Jetboil Joule group cooking system retails for $170, with the optional windscreen and hanging kit for $20.