Burner inserter

The burner inserter is the earliest inserter variant and moves items by burning fuel instead of drawing electricity from the power grid. It behaves like other inserters in most respects, but it has its own internal fuel inventory and energy buffer. When it is idle, it consumes no power, and unlike electric inserters it does not continuously draw maximum power while working.

A burner inserter spawns with 500 kJ of internal energy, which is 25% of the energy contained in one piece of wood fuel. When it runs out of fuel in its internal inventory, it can pull fuel from its input and use that fuel for itself, a behavior often called leeching. This is not a free action: the motion itself still consumes fuel, so fuel taken for self-power is also spent on operation.

In practice, burner inserters have the same basic transfer behavior as other inserters, but their runtime is limited by the fuel they carry. Referencing inserter power usage, a burner inserter consumes about 66.9 kJ per item transfer. That works out to just under 30 transfers from one wood, about 60 from coal, and about 179 from solid fuel. With solid fuel and a maximum speed of about 0.79 transfers per second—roughly one spin every 1.27 seconds—it can run at full speed for around 141 seconds before needing refueling.

Because of this, burner inserters are most useful in very early setups or in systems where fuel is already being produced nearby. They can also remain viable in fuel-fed recycling setups, since a recycler outputting one solid fuel every few seconds can sustain them for continuous operation.