RTEX-27: capacity and installation fit
The RTEX-27 provides 27 kW at 240 V in the same listed cabinet size as the RTEX-24. It is the higher-output option in Rheem’s three-circuit RTEX pairing. It can be worth comparing when a household needs more simultaneous hot-water capacity than the RTEX-24 provides, provided the electrical assessment supports the larger connected load.
Water Heating Experts helps homeowners in Palm Beach Gardens, Jupiter and nearby Palm Beach County compare the Rheem RTEX-27 with their current equipment. Start with the Rheem installation overview for the wider range, or use the specifications below to discuss this exact model. It heats water as it flows and has no stored-gallon capacity.
Electrical requirements for the RTEX-27
| Specification | Published 240 V requirement |
|---|---|
| Heating input | 27 kW |
| Supply | 240 V, single phase |
| Total unit current | 113 A |
| Dedicated circuit protection | 3 × 40 A double-pole breakers |
| Manufacturer wire listing | 3 × 8 AWG; 75°C insulation |
| Recommended household service | 200 A; electrical load assessment required |
These are the model-row values in Rheem’s July 2026 specification sheet, RH-TE-WH-SS Rev. 1. The household service recommendation is different from the heater’s branch-circuit protection. A qualified electrician must confirm available capacity, conductor sizing, circuit routing and applicable installation requirements. An existing tank-water-heater circuit should never be assumed to support this conversion.
The ratings here are specifically for 240 V. A property supplied at 208 V needs a separate performance and electrical review: lower voltage reduces heating output, so the 240 V flow figures do not carry over unchanged. Tell WHE about other large electrical loads or planned additions when discussing the project.
Flow depends on incoming water temperature
| Incoming water → outlet set point | Rheem flow example |
|---|---|
| 67°F → 105°F (38°F rise) | 4.9 GPM |
| 72°F → 105°F (33°F rise) | 5.6 GPM |
| 77°F → 105°F (28°F rise) | 6.6 GPM |
The current Rheem chart lists 4.9 GPM with 67°F inlet water and a 105°F outlet. Two 2 GPM showers leave about 0.9 GPM of headroom in that specific example, so adding a higher-flow faucet can still take demand above the illustrated output. At 77°F inlet, the chart lists 6.6 GPM. A higher desired outlet temperature changes both examples.
These are manufacturer sizing examples at a 105°F set point, not a recommendation for every household’s temperature setting. Your actual inlet temperature varies with the property and season. List the fixtures used together and their flow rates; bathroom count by itself does not describe the load. Higher outlet temperatures require more heating for each gallon and reduce available flow.
Controls, efficiency and everyday use
The RTEX-27 has digital temperature adjustment and modulates heating power as demand changes. Rheem lists 0.93 UEF for this model in the current specification table. UEF is a standardized efficiency rating, not a guaranteed percentage reduction in your electricity bill. Avoid comparing it directly with marketing statements about heating-element efficiency.
There is no storage tank to deplete, but the heater still has a limit on how much water it can heat at once. It also does not eliminate the water already sitting in long hot-water pipes. If your main concern is waiting for hot water at a distant bathroom, explain that separately from a problem with the heater keeping up once water arrives.
Dimensions, location and service access
Rheem’s July 2026 table lists 17 inches high × 17 inches wide × 3.625 inches deep, with bottom ¾-inch NPT water connections. These are cabinet dimensions, not the complete installation envelope. Allow space for plumbing, wiring, mounting and service access; confirm dimensions against the supplied unit before preparing the location.
The linked installation and owner’s manual specifies indoor installation and recommends 12 inches above and below the heater and 6 inches in front and at the sides. The location also needs protection from freezing, splashing and moisture. WHE reviews access and leak protection when assessing a replacement location.
Compare the RTEX-27 with nearby sizes
Moving from the RTEX-24 to the RTEX-27 adds 3 kW, or 12.5% rated heating input, while retaining three 40 A double-pole circuits. The published total current increases from 100 to 113 A. Moving up again to the RTEX-36 adds a fourth circuit and raises the recommended household service from 200 to 300 A. Those differences should be part of the installation comparison.
Compare Rheem RTEX-18, Rheem RTEX-24, Rheem RTEX-36, or browse the water heater model catalog. A suitable electric storage heater can also be part of the comparison when installation space, electrical work and the household’s usage are considered together.
Maintenance and limited warranty
Tankless equipment still needs maintenance. Water quality and scale affect the service plan, and the manufacturer calls for regular attention to plumbing connections. Ask about accessible service valves and maintenance needs when planning the installation. Keep the model and serial number, receipt and installation record available for future service.
Rheem’s limited warranty describes qualifying leak coverage for five years and component coverage for one year, subject to its terms and exclusions. Labor is not included in that manufacturer coverage. Coverage is determined by the applicable warranty and the cause of failure; it is not a promise of free installation or all repairs.
RTEX-27 questions
Does the RTEX-27 always deliver 6.6 GPM?
No. Rheem’s 6.6 GPM example uses 77°F incoming water and a 105°F set point. At 67°F inlet, the same chart lists 4.9 GPM. Colder inlet water, a higher outlet setting or lower supply voltage reduces the available heated flow.
Can an RTEX-27 replace an RTEX-24 without an electrical review?
The published branch-circuit count and breaker ratings match, but total current rises from 100 to 113 A. Existing wiring, protection, connections and service capacity still need verification. Matching circuit counts alone is not enough to approve an equipment change.
Can the RTEX-27 be installed outdoors?
The linked Rheem manual specifies indoor installation. WHE reviews a protected, accessible location and the space needed for service and connections before recommending the equipment.
Does the RTEX-27 need a gas line or vent?
It uses electric resistance heating, so it does not need a gas supply or combustion vent. The project still requires correctly designed electrical circuits, plumbing connections and an appropriate indoor location.
What does an installed RTEX-27 cost?
WHE quotes each installation individually after reviewing the heater, electrical requirements, plumbing and access. Send photos of the current installation and model label, and describe the fixtures that need hot water together. Equipment availability is confirmed during the estimate.
Ask WHE about the Rheem RTEX-27
For help comparing this model, text photos to 561-602-9062, call WHE or request a free installation estimate. Include your location and the problem you want the new heater to solve. Our installation service page explains the next steps.