🚿 Tankless Water Heater Flow Rate Calculator
Find the exact GPM capacity you need based on your fixtures, usage, and temperature requirements
| Temperature Rise (°F) | Climate Zone | Small Unit (3-4 GPM) | Medium Unit (6-8 GPM) | Large Unit (10+ GPM) |
|---|---|---|---|---|
| 35°F rise | Very warm / Southern | 1–2 fixtures | 3–4 fixtures | 5+ fixtures |
| 45°F rise | Moderate / Central US | 1 fixture | 2–3 fixtures | 4+ fixtures |
| 55°F rise | Cool / Midwest | 1 fixture low-flow | 2 fixtures | 3–4 fixtures |
| 70°F rise | Cold / Northern | 1 fixture low-flow | 1–2 fixtures | 2–3 fixtures |
| 80°F rise | Very Cold / Alaska | Sink only | 1 shower max | 2 fixtures |
| GPM | Litres / Min | Typical Use Case | Recommended Unit Type |
|---|---|---|---|
| 2.0 GPM | 7.6 L/min | 1 low-flow shower | Point-of-use electric |
| 3.5 GPM | 13.2 L/min | 1 shower + 1 sink | Small gas unit |
| 5.0 GPM | 18.9 L/min | 2 showers or shower + kitchen | Mid-range gas |
| 7.0 GPM | 26.5 L/min | 3 fixtures simultaneously | High-capacity gas |
| 9.5 GPM | 36.0 L/min | 4–5 fixtures whole home | Commercial / high-demand |
| 11.0 GPM | 41.6 L/min | 5+ fixtures large home | Dual unit or condensing |
| Home Type | Bedrooms | Peak Fixtures | Min GPM Needed | Recommended GPM |
|---|---|---|---|---|
| Studio / 1BR Apt | 0–1 | 1 shower + 1 sink | 3.0 GPM | 4–5 GPM |
| Small Home | 2 | 1 shower + sink + kitchen | 4.5 GPM | 6 GPM |
| Average Home | 3 | 2 showers + 2 sinks | 5.5 GPM | 7–8 GPM |
| Large Home | 4 | 2 showers + dishwasher + 2 sinks | 7.0 GPM | 9–10 GPM |
| Luxury / Estate | 5+ | 3+ showers + multiple appliances | 9.0 GPM | 11+ GPM |
Tankless water heaters give continuous warm water. Busy families like that they never stay without warm water. All models work for various situations, for instance gas, propane or electric versions.
Various makers offer domestic and business types, included hybrid heat pumps and storage tanks. A.O. Smith is famous mark in that field.
Tankless Water Heaters: Benefits, Cost, and Care
Their gas models have ENERGY STAR approval with 0.95 UEF efficiency. Also, they use X3 Scale Prevention Technology, that removes the need of yearly descaling.
Tankless water heaters cost at first more than usual storage models. The price of the device itself is at least double than that of same storage units. Even so, these devices usually last more long.
They use less energy and operate more cheap. Like this the savings can repay the high price. For instance, tankless system saves around 15 % of energy compared with storage.
Also, they do not use gas or electricity when water does not flow, so avoid cost because of standby heating. In some cases, putting each one needing heaters at every hot water tap, you can reach even bigger savings.
Installation differs to that of traditional storage models. Storage usually simply connect, but tankless one sometimes must set to outside wall. They can be more hard for show.
Some think, that for small families it does not worth the investment. But for users the care stays easy. You usually descale the unit yearly once.
It can cost only 5 USD using vinegar. If water is hard, you need to flush it yearly.
Different models have different features. Electric under sink versions are little and portable with a digital screen. They let you operate the temperature.
Rheem offer energy-saving domestic units. In a rural vehicle tankless heater reacts while water flow. It then delivers endless warm water, until the flow will end.
Some models automatic heat the water line, if the water in it starts to freeze. That helps during cold weather.
