Natural gas. 6-Year Tall Gas Water Heater. 40-gallon tank is suitable for families and includes extra durable high-temperature dip tube to meet the most stringent plumbing codes. Energy conserving low input pilot. Tank protected by exclusive porcelain formula. 76% recovery efficiency for more hot water. Thick non-CFC foam insulation, R-6.7. Factory installed temperature and pressure relief valve. 40 gallons. Size 58-1/2 high, diameter 18-1/2.