Guides / Water heaters · Updated
Rheem RTEX-27: breakers, wire and gpm for your water
From Rheem's own spec sheets, read November 2026.
Short answer
The Rheem RTEX-27 draws 113 A at 240 V and needs three 40 A double-pole breakers. Rheem recommends at least 200 A electrical service. With 37°F winter water it makes 2.7 gpm of 105°F water; with 77°F water, 6.6 gpm.
Flow by incoming water temperature
| Incoming water | 37°F | 42°F | 47°F | 52°F | 57°F | 62°F | 67°F | 72°F | 77°F |
|---|---|---|---|---|---|---|---|---|---|
| gpm at 105°F | 2.7 | 2.9 | 3.2 | 3.5 | 3.8 | 4.3 | 4.9 | 5.6 | 6.6 |
A shower uses 2.0 gpm with a WaterSense head or 2.5 gpm with a standard one, so divide by that for showers at once. Rheem's product page also shows 4.9 gpm as its maximum; its spec sheet table runs to 6.6 gpm with 77°F water. We use the spec sheet.
Specs
| Power | 27 kW at 240 V |
|---|---|
| Current | 113 A |
| Breakers | three 40 A double-pole |
| Wire | three runs of 8 AWG |
| Recommended service | 200 A |
| Starts at | 0.3 gpm |
| UEF | 0.93 |
Can your panel run it?
113 A is a big share of any house. The electric water heater circuit check adds it to your house's load and tells you whether your main breaker has room. For a gas or heat pump alternative, compare running costs with the water heater cost calculator.