Know exactly how many tanks to bring — and what it'll cost
🔥 Heater
🛢️ Propane Tank
📅 Trip Details
All calculations use the verified energy content of propane and official Mr. Heater specifications:
| Model | BTU Settings | Run time on 1 lb cylinder | Coverage |
|---|---|---|---|
| Little Buddy | 3,800 BTU (fixed) | ~5.6 hrs | Up to 95 sq ft |
| Portable Buddy (MH9BX) | 4,000 / 9,000 BTU | ~5.4 hrs (low) / ~2.4 hrs (high) | Up to 225 sq ft |
| Big Buddy (MH18B) | 4,000 / 9,000 / 18,000 BTU | Uses 2 × 1 lb (up to 11 hrs dual tanks) | Up to 450 sq ft |
Sources: Mr. Heater Portable Buddy spec page · Mr. Heater Big Buddy spec page
A heater running at 50% duty cycle uses half the propane of one running continuously — yet the shelter stays nearly as warm because radiant heat builds up. Ice fishing forum regulars consistently report that their Portable Buddy cycles on for 15–20 minutes, heats the shelter, then turns down or shuts off for a similar period. Adjusting the duty cycle input to match your real conditions is the single biggest accuracy improvement over a simple "BTU ÷ tank" calculation.
How long does a 1 lb propane tank last in a Mr. Heater Portable Buddy?
At the 4,000 BTU low setting, a 1 lb cylinder lasts about 5.4 hours continuously, or roughly 10+ hours at 50% duty cycle. At the 9,000 BTU high setting, continuous run time is about 2.4 hours, or ~4.8 hours cycling. Use this calculator with your real duty cycle for a personalized estimate.
How many propane tanks do I need for a full day of ice fishing?
For an 8-hour trip in a typical hub shelter with a Portable Buddy on low at 50% duty cycle, you need roughly 0.75 of a 1 lb tank — so one cylinder is usually enough. On high (9,000 BTU) at 50% duty, you'd use about 1.7 lb of propane, meaning two 1 lb cylinders. A 5 lb tank covers most day trips at any setting.
How much propane does a Mr. Heater Big Buddy use per hour?
The Big Buddy burns approximately 0.186 lb/hr at 4,000 BTU, 0.417 lb/hr at 9,000 BTU, and 0.834 lb/hr at 18,000 BTU. Running dual 1 lb cylinders at 4,000 BTU, the two tanks together last about 10.7 hours continuously. At 50% duty cycle that stretches to over 21 hours.
Is a 20 lb propane tank worth it for ice fishing?
For trips longer than one day, or if you fish every weekend, a 20 lb tank with a hose-and-filter kit is far more cost-effective than 1 lb cylinders. The propane cost per BTU is roughly 4–6× lower from a 20 lb tank exchanged at a big-box store than from individual 1 lb canisters. The trade-off is weight and setup time.
Why does my heater run out of propane faster in extreme cold?
Liquid propane must vaporize before it can burn. The vaporization rate slows significantly below about 0 °F (−18 °C) as tank pressure drops. The gas flow becomes insufficient to sustain the flame, causing the heater to sputter or shut off even when propane remains in the tank. Pre-warming spare cylinders inside the shelter keeps them above the pressure threshold.
Is it safe to use a propane heater inside an ice fishing shelter?
Mr. Heater Buddy models are rated for indoor use and feature an Oxygen Depletion Sensor (ODS) that shuts the heater off if oxygen drops to unsafe levels. Per Mr. Heater guidelines, maintain at least 4 inches of ventilation at floor level and at the ceiling. Never run the heater while sleeping, and always keep a battery-powered CO detector inside the shelter. See Mr. Heater's safety documentation for complete guidance.