| Properties | Hydrogen | Comparison |
|---|---|---|
| Density (gaseous) | 0.089 kg/m3 (0°C, 1 bar) | 1/10 of natural gas |
| Density (liquid) | 70.79 kg/m3 (–253°C, 1 bar) | 1/6 of natural gas |
| Boiling point | –252.76°C (1 bar) | 90°C below LNG |
| Energy per unit of mass (LHV) | 120.1 MJ/kg | 3x that of gasoline |
| Energy density (ambient cond., LHV) | 0.01 MJ/L | 1/3 of natural gas |
| Specific energy (liquefied, LHV) | 8.5 MJ/L | 1/3 of LNG |
| Flame velocity | 346 cm/s | 8x methane |
| Ignition range | 4–77% in air by volume | 6x wider than methane |
| Autoignition temperature | 585°C | 220°C for gasoline |
| Ignition energy | 0.02 MJ | 1/10 of methane |
Notes: cm/s = centimetre per second; kg/m3 = kilograms per cubic metre; LHV = lower heating value; MJ = megajoule; MJ/kg = megajoules per kilogram; MJ/L = megajoules per litre.
Source: The Future of Hydrogen: Seizing today’s opportunities, IEA, June 2019.