My neighbor Dave called me in a panic three winters back. His 40-gallon tank had just died on a Sunday, no plumber available until Tuesday, and four teenagers in the house who all wanted showers before school. He ended up at Home Depot buying a Rheem RTEX-24 off the shelf because it was the only thing in stock that didn’t need a gas line or a permit wait. Three years later, he still has it, and that’s basically the whole story of why this unit sells 100+ units a month on Amazon with over 4,000 reviews behind it.
The Rheem RTEX-24 is a 24kW, 240-volt electric tankless water heater rated for up to 5.9 gallons per minute (GPM), designed to supply hot water to a small to mid-sized home without a storage tank, gas line, or venting. It runs about $549 on Amazon, carries a 4.2 out of 5 star rating across more than 4,000 reviews, and is one of the best-selling electric tankless units in its category. It is not the cheapest option and it is not the largest, but it hits a specific sweet spot: whole-home coverage for smaller households at a price most homeowners can justify without financing.
What the RTEX-24 Actually Is
Rheem builds the RTEX-24 with three separate copper immersion heating elements, each one doing part of the work so the unit only draws the power it actually needs at any given moment. This is called self-modulation, and it’s the reason the unit can claim high efficiency instead of just blasting full power the second you open a tap.
The unit weighs about 17.8 pounds and mounts on a wall, connecting to your plumbing through a 3/4 inch NPT fitting on the bottom. There’s no tank, no pilot light, and no venting to worry about because electric resistance heating doesn’t produce combustion byproducts the way gas units do.
Rheem RTEX-24 Specs at a Glance
| Spec | Detail |
|---|---|
| Power | 24 kW at 240V |
| Max flow rate | 5.9 GPM (manufacturer rated; some retailers list 4.68 GPM at a 45degF temperature rise) |
| Weight | 17.8 lbs |
| Heating elements | 3 copper immersion elements |
| Connection | 3/4” NPT, bottom-mounted |
| Amazon price (2026) | $549.00 |
| Amazon rating | 4.2 out of 5 (4,044+ ratings) |
| Home Depot rating | 3.9 out of 5 (2,814 reviews) |
That gap between the 5.9 GPM figure Rheem advertises and the 4.68 GPM Home Depot lists is not a typo war, it’s a temperature-rise difference. Flow rate on any electric tankless unit drops as the incoming water gets colder, because the unit has a fixed amount of power to raise the temperature. More on that in a minute.
Why the Reviews Are So Split
With 4,000+ reviews, you’re going to see a real spread of experiences, and the honest version of this review has to include the negative ones, not just the highlight reel.
The most common praise, based on patterns across both Amazon and Home Depot reviews: people love not running out of hot water mid-shower, installation was more straightforward than expected for those with existing 240V electrical capacity, and several reviewers specifically mention it successfully replaced a 50-gallon tank in a 2-3 bathroom house.
The most common complaints, based on the same review pool: inconsistent water temperature (usually tied to undersized electrical service or high simultaneous demand), and error codes appearing after a period of normal use, which usually point to a flow sensor issue or a failing heating element rather than a fundamentally broken unit.
Home Depot’s review data (3.9 stars across 2,814 reviews) runs slightly lower than Amazon’s (4.2 stars across 4,044+ reviews). That’s a meaningful data point on its own: the RTEX-24 performs well for most buyers, but a meaningful minority hit friction, and that friction is almost always tied to either home electrical capacity or water hardness, not the unit’s core engineering.
Who This Unit Actually Works For
Based on the specs and the GPM math, the RTEX-24 is built for:
- A small to mid-sized home (roughly 1-3 bathrooms)
- Warmer to moderate climates, where incoming groundwater temperature doesn’t force a big temperature rise
- Homeowners who already have or can add 3 dedicated 40-amp double-pole breakers and adequate panel capacity
- Someone replacing a tank of 40-50 gallons or smaller
It is not the right unit for a large home running multiple showers plus a dishwasher and washing machine at once, especially in a cold climate. Rheem makes larger units in the same RTEX line (13kW, 18kW, 27kW, 36kW) specifically because one size doesn’t fit every household, which is worth knowing before you buy based on price alone.
The Electrical Reality Nobody Mentions on the Product Page
This is the part that trips up first-time tankless buyers the most. The RTEX-24 needs three 40-amp double-pole breakers, which is a serious electrical load, not a simple swap-and-go appliance. If your electrical panel doesn’t have three open double-pole slots or the amperage headroom to support it, you’re looking at an electrician visit before you ever turn the unit on.
The National Fire Protection Association (NFPA), which publishes the National Electrical Code (NEC) used across the US, notes that residential electrical services are sized based on total home load, and major 240V appliances need to be accounted for in that calculation (NFPA, “5 Key Considerations for Single Family Residential Electrical Services Based on the 2020 NEC,” Corey Hannahs, Jan 2022). That’s a general code reference, not RTEX-24-specific guidance, but it explains why so many reviewers mention needing an electrician even for a “simple” tankless swap.
Should You Buy It?
If you have a small to mid-sized home, live somewhere with moderate groundwater temperatures, and either already have the electrical capacity or are budgeting for an electrician, the RTEX-24 is a legitimately good value at $549. The 4.2-star rating across 4,000+ purchases backs that up. If you’re in a cold climate with multiple bathrooms running simultaneously, look at Rheem’s larger RTEX models or a different brand entirely before committing.
If you want the actual unit, here it is on Amazon:
Rheem RTEX-24 24kW 240V Electric Tankless Water Heater - View on Amazon
If you already own one and it’s due for basic upkeep, these are the same accessories that show up repeatedly in the RTEX-24 review threads:
Rheem SP20060 Electric Water Heater Tune-Up Kit - View on Amazon
For a deeper look at what it actually costs to run this unit month to month, see our full Rheem RTEX-24 price breakdown.
The Bottom Line
The Rheem RTEX-24 is a well-reviewed, reasonably priced electric tankless water heater that works well for smaller homes with adequate electrical capacity. It is not a magic fix for a house that needs a bigger unit, and it is not a DIY-only project if your panel isn’t already set up for it. Go in with realistic expectations about sizing and electrical prep, and the 4.2-star track record across thousands of real buyers holds up.
Frequently Asked Questions
Is the Rheem RTEX-24 good for a whole house? It can supply a whole house if that house is small to mid-sized, roughly 1 to 3 bathrooms, with moderate simultaneous hot water demand. For larger homes or homes with 4+ bathrooms, Rheem’s bigger RTEX models (27kW or 36kW) are a better fit.
How many amps does the Rheem RTEX-24 need? The RTEX-24 requires three 40-amp double-pole breakers, which is a significant electrical load that most standard panels need to be checked for before installation.
What is the flow rate of the Rheem RTEX-24? Rheem rates it at up to 5.9 GPM, though real-world flow rate depends on incoming water temperature. Home Depot’s listing shows 4.68 GPM at a 45-degree temperature rise, which is a more conservative real-world figure for colder climates.
Does the Rheem RTEX-24 need venting? No. As an electric resistance water heater, it produces no combustion byproducts and does not require venting, unlike gas tankless units.
How long does a Rheem RTEX-24 last? Rheem does not publish a specific lifespan figure for the RTEX-24, but electric tankless units in this class are generally expected to last 15-20 years with basic maintenance like periodic descaling in hard water areas.
Why does my Rheem RTEX-24 show an error code? Error codes on the RTEX-24 most commonly point to a flow sensor fault or a failing heating element, both of which are addressed in our dedicated error codes guide.
Is the Rheem RTEX-24 worth it compared to a tank water heater? For smaller households with moderate hot water demand, many owners report it pays for itself over time through reduced standby energy loss, since it only heats water on demand instead of maintaining a full tank at temperature around the clock.
Can I install the Rheem RTEX-24 myself? The plumbing connection is straightforward, but the electrical work (three 40-amp double-pole breakers) is a licensed electrician job in most jurisdictions and is not recommended as a DIY project unless you are a qualified electrician yourself.
What’s the difference between the RTEX-24 and RTEX-18? The RTEX-24 delivers more power (24kW vs 18kW) and a higher flow rate, making it better suited to slightly larger homes or colder climates where more heating capacity is needed to hit the same output temperature.
Does the Rheem RTEX-24 work in cold climates? It works, but flow rate drops as incoming groundwater temperature drops, since the unit has a fixed power budget to raise water temperature. Homes in cold climates may need a larger RTEX model to maintain the same usable flow rate as a warmer climate.
References
- Amazon.com product listing and customer review data for Rheem RTEX-24, accessed July 2026: https://www.amazon.com/dp/B01MS9DVEE
- NFPA, “5 Key Considerations for Single Family Residential Electrical Services Based on the 2020 NEC,” Corey Hannahs, January 6, 2022: https://www.nfpa.org/News-Blogs-and-Articles/Blogs/2022/01/06/Considerations-for-Single-Family-Residential-Electrical-Services-Based-on-the-2020-NEC
- TanklessHeat.org, “Rheem RTEX-24 Residential Tankless Water Heater Review,” William Fisher: https://www.tanklessheat.org/rheem-rtex-24-review/