It depends on what type of water heater do you have. For a gas-heater, 75 gallons is considered large. For the electric heater, 120 gallons is considered large.
Instant water heaters, commonly known as on demand or tankless water heaters are available at large home improvement stores such as Lowes or Home Depot, or wherever water heaters are sold.
Electric geysers or electric water heaters as they are sometimes called come in a variety of different capacities with the usual range being between 100 and 300 litres capacity for domestic installations. Larger capacities are available for use in industrial an commercial installations for example hotels and hospitals.
Yes, the tankless water heaters do cost more than the normal water heaters because tankless water heaters are designed to supply hot water only when needed unlike normal ones.
American Water Heaters.
American Water Heaters
Electric water heaters have not carbon monoxide.
Unlike storage water heaters where a large quantity of water is kept heated all the time, the instant water heaters heat the water during passage. It does take a few seconds for hot water to reach but it save a lot of money while saving electricity.
Common sizes (in gallons) are 20, 30, 40, 50, 66, and 80.
You can buy water heaters from any home hardware store.
GE hot water heaters are made by Rheem.
Rheem provide a series of high efficiency gas water heaters. Several different companies also provide tank-less water heaters, which are very efficient, as well as solar water heaters.
"Rheem does manufacture both gas and electric water heaters. Rheem currently offers 18 different varieties of gas water heaters and 9 different varieties of electric water heaters. Both types of Rheem water heaters are known for their rigorous standards, reliability, and efficiency."