Amazon’s own AI-generated summary of RTEX-24 reviews doesn’t sugarcoat anything: alongside genuine praise, it directly states that “reliability is a concern as units fail after 10 months of use” for some buyers, and flags “heating performance issues” as a recurring theme. That’s coming straight from an aggregation of the actual review text, not speculation, so let’s walk through what’s really going wrong for the buyers who report problems.
The most common Rheem RTEX-24 problems reported by verified owners include heating element failures, inconsistent water temperature, wiring harness issues, and sensor or control board faults, with some units experiencing failures within the first year of use. These issues aren’t universal (the unit maintains a 4.2-star rating across more than 4,000 reviews), but they appear often enough across detailed reviews to take seriously before you buy.
Heating Element Failures
This is the most frequently documented issue across detailed verified reviews. The RTEX-24’s three copper immersion elements are a serviceable design (several reviewers describe replacing a single element in about 30 minutes), but element failure itself shows up repeatedly, sometimes within the first year of ownership.
One particularly detailed verified review documented replacing “every single part” of an 18kW RTEX unit over roughly two years, including multiple heating elements, before ultimately replacing the entire unit, and reported the same failure pattern recurring on the replacement unit as well. That reviewer specifically flagged hard water and mineral buildup as a likely contributing factor, since scale accumulation on heating elements is a documented cause of premature failure across the entire tankless water heater category, not unique to Rheem.
Inconsistent Water Temperature
Amazon’s aggregated review summary specifically calls out “mixed experiences with water temperature,” with some buyers reporting the water is “plenty hot” while others say it “doesn’t get hot enough.” Based on the detailed reviews available, this pattern most often traces back to two root causes: insufficient electrical capacity (running the unit below its full three-element capability due to panel limitations) or cold groundwater temperature requiring more temperature rise than the household’s electrical setup can fully support.
Wiring and Component Failures
Beyond the heating elements themselves, several detailed reviews describe wire harness arcing, control board failures, and sensor faults. One reviewer described a wire harness that began “arcing and fused together melting off and almost catching fire,” which tripped the breaker before causing more serious damage. This is a serious safety-relevant complaint, and it underscores why proper installation, particularly secure wiring connections, matters enormously with a unit drawing this much current.
The E5 Error and Flow-Related Faults
Multiple reviews reference an “E5” error code appearing during use, generally associated with flow or heating demand exceeding what the unit’s current configuration can support. This ties directly back to the electrical capacity and groundwater temperature issues covered elsewhere in this guide, the error often shows up when a household’s real-world demand exceeds what their specific installation (voltage, panel capacity, incoming water temperature) can actually deliver, rather than indicating a random defect.
How Common Are These Problems, Really?
It’s worth keeping these complaints in perspective. The RTEX-24 maintains a 4.2 out of 5 star rating across more than 4,000 Amazon reviews, meaning the majority of buyers report a positive experience. Home Depot’s data shows a slightly lower but still respectable 3.9 stars across 2,814 reviews. The documented problems are real and worth planning around, but they represent a meaningful minority of the overall review pool, not the typical experience.
How to Reduce Your Risk of These Problems
Based on the patterns in verified reviews, a few practical steps can meaningfully reduce your odds of running into these issues: ensure your electrical installation is done by a qualified, licensed electrician with secure, properly rated connections; consider a water softener or regular descaling schedule if you have hard water, since mineral buildup is a documented contributor to element failure; and confirm your unit is correctly sized for both your fixture count and your local groundwater temperature, since undersizing appears to be a common root cause behind both temperature inconsistency and error codes.
For a complete breakdown of Rheem’s specific error codes and what they mean, see our error codes guide.
Rheem RTEX-24 24kW 240V Electric Tankless Water Heater - Check Current Price on Amazon
If you’re troubleshooting a failed element, this replacement part shows up frequently in real owner discussions:
HE 90240 Heating Element Replacement for Rheem RTEX-18/24/27 - View on Amazon
The Bottom Line
The Rheem RTEX-24’s most common documented problems, heating element failures, inconsistent temperature, and occasional wiring or sensor faults, are real but affect a minority of the overall review pool. Proper installation, attention to water hardness, and correct sizing meaningfully reduce your risk of encountering them.
Frequently Asked Questions
What are the most common problems with the Rheem RTEX-24? Based on verified reviews, the most common issues include heating element failures, inconsistent water temperature, and occasional wiring or control board faults, with some units failing within the first year of use.
Why does my Rheem RTEX-24 have inconsistent water temperature? This most often traces back to insufficient electrical capacity for your household’s demand or cold groundwater requiring more temperature rise than your setup can fully support.
Is the Rheem RTEX-24 unreliable? Not overall. It maintains a 4.2-star rating across more than 4,000 Amazon reviews, meaning most buyers report a positive experience, though a documented minority experience component failures.
What causes heating elements to fail on the Rheem RTEX-24? Hard water and mineral buildup on the elements is a commonly cited contributing factor, based on detailed reviewer accounts, though element failure can also occur independent of water hardness in some cases.
What is the E5 error on the Rheem RTEX-24? It’s generally associated with flow or heating demand exceeding what the unit’s current configuration can support, often linked to electrical capacity or groundwater temperature limitations rather than a random defect.
How long do Rheem RTEX-24 heating elements typically last? This varies significantly based on water hardness and usage. Some units run for years without issue, while others experience element failures within the first year, particularly in hard water areas without regular maintenance.
Can I fix a heating element problem myself? Yes, several verified reviewers describe replacing a single failed element in about 30 minutes using basic tools, after properly shutting off the breaker and water supply first.
Is the wiring harness issue dangerous? Potentially, yes. At least one verified reviewer described arcing that could have caused a fire, underscoring the importance of proper, licensed electrical installation with secure connections.
Does hard water make Rheem RTEX-24 problems worse? Yes, mineral buildup on heating elements from hard water is a commonly cited contributing factor to premature element failure across the tankless water heater category generally, not unique to Rheem.
Should these problems stop me from buying the RTEX-24? Not necessarily. The unit’s overall 4.2-star rating reflects a mostly positive ownership experience. Understanding these documented risks helps you take preventive steps, like proper installation and water hardness management, to reduce your odds of encountering them.
References
- Amazon.com AI-generated review summary and individual verified customer reviews for Rheem RTEX-24, accessed July 2026: https://www.amazon.com/dp/B01MS9DVEE
- Home Depot customer review data for Rheem RTEX-24, accessed July 2026