A full 20 lb propane tank used for heating typically lasts around 10–20 hours of continuous use, depending mainly on the heater’s BTU rating and your heat setting. In practical, on‑and‑off real-world use, many people see anywhere from a couple of chilly evenings to several shorter sessions from a single tank.

Key numbers for a 20 lb tank

  • A standard 20 lb tank holds about 4.7 gallons or roughly 430,000 BTUs of propane.
  • Many portable propane heaters for garages, tents, or patios run in the 10,000–40,000 BTU per hour range.
  • Rule of thumb: burn time ≈ 430,000÷heater BTU per hour430{,}000\div \text{heater BTU per hour}430,000÷heater BTU per hour (at full power, continuous).

Approximate run times by heater size

These are ballpark continuous runtimes at full output:

  • 10,000 BTU heater: up to about 40 hours.
  • 20,000–22,000 BTU heater: roughly 18–22 hours.
  • 30,000 BTU heater: around 14 hours.
  • 30,000–40,000 BTU patio/garage heater: about 10–12 hours.
  • 50,000 BTU high-output appliance: roughly 8–9 hours.

Because most people don’t run heaters on max the whole time, light or intermittent use can stretch that to 18–20 hours or more of total heating time over multiple sessions.

Simple way to estimate for your heater

  1. Find your heater’s BTU rating on the label or manual.
  2. Use:

Hours≈430,000BTU rating per hour\text{Hours}\approx \frac{430{,}000}{\text{BTU rating per hour}}Hours≈BTU rating per hour430,000​

  1. If you usually run it on medium (say half power), you can roughly double that number.

Example:

  • 30,000 BTU garage heater → 430,000÷30,000≈14430{,}000\div 30{,}000\approx 14430,000÷30,000≈14 hours on high.
  • Run about half the time or at a lower setting, and that same tank might cover several evenings of use.

Safety and cold-weather notes

  • Always use propane heaters only where they are rated (indoor-safe vs outdoor-only) and follow ventilation requirements to avoid carbon monoxide buildup.
  • In very cold weather, propane pressure drops and heaters may perform less efficiently or shut off sooner, so real-world runtimes can be a bit shorter than the math suggests.

Quick SEO-style summary

  • Main focus term: how long will a 20 lb propane tank last for heating
  • Typical answer: about 10–12 hours at 30,000–40,000 BTU/h, with a range of roughly 8–20+ hours depending on heater size and settings.
  • People online often share forum and video tests showing 30,000 BTU class heaters running around 14 hours and smaller units stretching well past 20 hours on a single tank.

Information gathered from public forums or data available on the internet and portrayed here.