Tank-style water heaters heat and store hot water so it is ready for use as needed.
Residential-sized tank water heaters, with capacity 30-40 gallons, are generally used in residential and small commercial settings. Larger heaters, of capacity around 100 gallons, are common in commercial and small industrial applications.
Tank-style water heaters can be used in combination heating and hot water systems, or used as backup to a solar water heating system.
III Equipment Options
Tank water heaters range in heating capacity from 30,000 BTU/hr (for residential units) up to 199,000 BTU/hr (for commercial units). This seemingly unusual upper limit results from codes; units rated higher than 200,000 BTU/hr are generally classified as boilers.
Tank-style water heaters are available with atmospheric vent, direct vent or power vent options.
Modern tank water heaters will generally be at least 62% efficient. Condensing models, which condense the heater's flue gases, can be higher than 90% efficient and are currently available for commercial applications.
1. Equipment Manufacturer Database
2. Natural Gas Efficiency Consortium