It is the first question every off-grid buyer asks, and the honest answer begins with hourly gas consumption. A heater's burn rate is set by its heat output, and SEFFY's two portable models publish theirs: 600 g/h at 10 kW and 360 g/h at 6 kW. From those two figures you can plan a trip instead of guessing. The heat always comes from the LPG canister; the ignition and the 25 W pump always come from the built-in 5200 mAh battery — so before you rely on any of this, the battery must be charged and the canister must be fitted.

Gas use is roughly proportional to heat load — about 60 g of LPG per kilowatt-hour as a working rule. So 10 kW → 600 g/h and 6 kW → 360 g/h. Put a 5 kg (5000 g) cylinder underneath and the math is simple division: about 8.3 hours of continuous operation at 10 kW, or about 13.9 hours at 6 kW. Real trips are intermittent — showers, dishes, a rinse — so calendar life stretches further. The hourly figure is your planning floor, not a timer that starts the moment you leave.

One nuance buyers miss: those runtimes assume the burner holds its rated output. In practice your gas use also tracks how cold the inlet is. A bigger temperature rise — heating from a 4 °C stream instead of a 20 °C tap — asks the burner for more energy per litre, so a cold-inlet trip burns the cylinder faster than the steady 8.3 h / 13.9 h ceiling suggests. Plan from the floor, then add margin for cold water.

The hourly figures feel abstract until you pencil a trip. Four 6-minute showers at roughly 4 L/min, warmed about 20 K, is around 96 litres and roughly 170 g of gas — a small slice of a 5000 g cylinder. Even the gentler 6 kW burner covers a weekend of showers and dishes on a single cylinder with margin to spare. The 8.3 h and 13.9 h numbers are the continuous ceiling; real, intermittent use sits far below it, which is why one cylinder routinely outlasts a trip.

The Thermostatic (10 kW, 600 g/h, 55 K max rise) suits high-demand, cold-inlet use where you want the most hot water per minute. The FLUE TYPE (6 kW, 360 g/h, 25 K max rise) suits lighter, warmer-climate duty where the smaller burn saves gas across a longer trip. Both draw ignition and pump power from the same charged battery — charge it; fit the canister.

• "What is the published gas consumption in g/h at full output?" — 600 and 360 are the figures; a vendor who only says "efficient" is hiding the number.
• "How many continuous hours does a 5 kg cylinder give at each burner?" — 8.3 h and 13.9 h are the planning floor; ask whether they assume a full cylinder.
• "Is the 60 g/kW·h figure a spec or a rule of thumb?" — treat it as an approximation; confirm the actual g/h for your model.
• "How is the battery recharged, and how long does a charge last for ignition and pump?" — Type-C, 12 V car, and power bank are the three paths.
• "What canister types fit?" — propane, high-mountain, butane, and LPG should all be supported for real off-grid flexibility.

• The hourly burn is for continuous use. Real trips last longer because you are not heating 24/7 — but plan from the hourly floor.
• 8.3 h / 13.9 h assume a full 5 kg cylinder and steady output. Carry a spare canister for multi-day trips; a half-empty cylinder halves the math.
• Gas gives the heat; the battery gives ignition and pump. Charge the battery and fit the canister before you depend on hot water — one without the other does nothing.
• Outdoor use only. Never run it in a tent, a cabin, or a vehicle. Combustion produces CO, which is colorless, odorless, and toxic.

Gas use scales with heat output, and the two portable burners publish theirs: 600 g/h at 10 kW and 360 g/h at 6 kW. On a full 5 kg cylinder that is roughly 8.3 hours or 13.9 hours of continuous hot water — more in real, intermittent use. Choose the burner to the trip, keep a spare canister, and remember the simple rule that never changes: gas for heat, a charged battery for ignition and pump, and both ready before you expect a shower. Outdoors only.