EcoSmart ECO 24 review: the heater is the cheap part
At roughly $420 it is one of the better-value electric tankless units you can buy. The problem is that installing it correctly costs more than buying it, and almost nothing in the listing tells you that.
On this page
Start with the number that decides everything, because it is not the one on the box: this heater draws 100 amps.
That is not a footnote. A 24 kW element bank at 240 volts pulls 100 amps continuously, split across three 40 amp double-pole breakers, and it needs conductors and a panel rated to carry that. The heater costs about $420. Getting 100 amps to the wall it hangs on costs between $400 and $2,500 depending on what your service looks like today, and if you are on a 100 amp supply it is not a wiring job at all — it is a service upgrade.
Once that is understood, this is a good product at a fair price.
| Specification | EcoSmart ECO 24 |
|---|---|
| Output | |
| Rated power | 24 kW at 240 V |
| Heat output | 81,891 BTU/hr |
| Advertised flow rate | 5.8 GPM Manufacturer figure. It is a real number at a very small temperature rise, and not the number you will see in winter — the rows below are the same unit at rises you will actually meet. |
| Real flow rate | |
| At 35 °F rise (Florida, summer) | 4.7 GPM |
| At 50 °F rise (mid-Atlantic) | 3.3 GPM |
| At 70 °F rise (northern winter) | 2.3 GPM A standard shower head is 1.8 to 2.5 GPM. Divide this row by that to get the honest fixture count. |
| Electrical | |
| Current draw | 100 A at 240 V |
| Breakers required | 3 × 40 A double-pole |
| Service implication | Needs 100 A of spare capacity in the panel On a 100 A service this is usually a panel upgrade before it is a water heater purchase. |
| Physical | |
| Dimensions (W × H × D) | 17 in × 17 in × 3.5 in |
| Weight | 14.3 lb |
| Mounting | Wall |
| Heat exchanger material | Copper |
| Control | |
| Maximum set temperature | 130 °F |
| Modulation | Self-modulating, patented |
| Display | Digital output temperature, 1 °F increments |
| Plumbing | |
| Connections | 3/4 in NPT |
| Ownership | |
| Country of manufacture | United States |
| Warranty | Lifetime on electronics, exchanger and element — original owner, original installation address, professional install required |
| Model number | ECO24 |
The 5.8 GPM on the listing is arithmetic, not a lie
Every tankless heater is advertised at the smallest temperature rise the manufacturer can defend. EcoSmart quotes 5.8 GPM for the ECO 24, and that figure is genuinely achievable — at a rise of about 28 °F, which is to say heating 70 °F groundwater to 98 °F. Almost nobody wants a 98 °F shower.
The arithmetic is fixed and you can do it yourself. A BTU raises one pound of water one degree Fahrenheit, water weighs 8.34 lb per gallon, so:
GPM = BTU output ÷ (temperature rise × 8.34 × 60)
24 kW is 81,891 BTU per hour, and electric resistance heating is effectively 100% efficient at the point of use, so all of it reaches the water. Divide it out:
- 35 °F rise — south Florida, summer — 4.7 GPM
- 50 °F rise — mid-Atlantic, spring — 3.3 GPM
- 70 °F rise — northern tier, January — 2.3 GPM
A standard shower head runs 1.8 to 2.5 GPM. So in Florida this is two showers and a sink. In Minnesota in winter it is one shower, and running the kitchen tap at the same time will be noticeable.
This is not an EcoSmart failing — it is physics, and every electric unit in this class faces it. It is a sizing failing, and it is why the single most common one-star review of every electric tankless heater on the market says the same thing: it worked fine until winter. Groundwater temperature is what sets your rise, and it swings from roughly 75 °F in south Florida to 42 °F across the northern tier. Our our tankless sizing calculator runs this against a regional dataset, and how to size a tankless water heater explains the method in full.
What the 100 amp draw actually costs
This is the part of the purchase that is invisible until an electrician is standing in your basement.
A 24 kW heater is, from the panel's point of view, roughly the same load as an electric range and an electric dryer running simultaneously and never stopping. Continuous loads are also derated: the NEC requires conductors and overcurrent protection sized at 125% of a continuous load, which is why three 40 amp breakers cover a 100 amp draw rather than the 100 amps you might expect from arithmetic alone.
What that means in practice, by starting condition:
- 200 amp service, spare capacity, panel near the install point. Three double-pole breakers, a short conductor run, a subpanel if spaces are tight. Commonly $400 to $900.
- 200 amp service, full panel. Add a subpanel and the feeder to it. $900 to $1,800.
- 100 amp service. A load calculation will almost certainly fail. You are looking at a service upgrade — new meter base, new panel, possibly a new drop — before the heater can go in at all. $2,500 to $6,000, and utility scheduling.
breaker and wire sizing for tankless heaters goes through the load calculation itself, including how to work out whether your existing service can take it before you call anyone.
The honest summary: on the right house this is a $420 heater. On the wrong house it is a $420 heater attached to a $4,000 electrical project. Nothing in the product listing distinguishes between those two houses, and that gap is where most of the disappointment with electric tankless heaters lives.
Self-modulation is the feature worth paying for
EcoSmart's patented self-modulation is the thing that separates this from cheaper units, and it is worth understanding because it is genuinely the difference between a pleasant shower and an irritating one.
A non-modulating heater switches elements on and off in fixed stages. Demand a little hot water and it overshoots; demand a lot and it undershoots, then corrects, then overshoots again. You feel this as the temperature wandering while you stand under it.
A self-modulating unit varies power continuously against measured flow and inlet temperature. It draws 8 kW for a hand wash and 24 kW for a shower, and the output temperature stays where you set it. On the ECO 24 this works well — it is the most consistently praised aspect of the unit across its 338 Amazon ratings, and it is the reason the 4.5 star average sits above the Rheem RTEX-18's 4.2 despite the Rheem having six times as many reviews.
The digital display sets temperature in 1 °F increments up to 130 °F. That ceiling is lower than the 140 °F Rheem and Rinnai permit. For domestic hot water 120 °F is the recommended setting anyway, so the practical impact is small — but if you were planning to run a dishwasher without an internal booster heater, check its requirement first.
Where it sits against the alternatives
Three comparisons matter, and the listing avoids all of them.
Against the Rheem RTEX-18 — the closest thing to a direct competitor, priced within $5. The EcoSmart gives you 24 kW to the Rheem's 18 kW, which is a third more hot water for the same money. The Rheem gives you two 40 amp breakers instead of three, which matters if your panel is short on physical spaces rather than on capacity. On output per dollar the EcoSmart wins clearly. Our Rheem RTEX-18 review: priced against a bigger heater covers the other side.
Against the Stiebel Eltron Tempra 29 Plus — $695 against $420, 28.8 kW against 24 kW. The extra money does not buy proportionally more hot water; it buys Advanced Flow Control, which throttles flow to hold your setpoint rather than letting the temperature sag when you exceed capacity. In a cold climate that single feature is the difference between a weaker shower and a cold one. Stiebel Eltron Tempra 29 Plus review: the one that tells you the truth explains why that matters more than the kilowatt difference.
Against gas — this is the comparison most people should run and few do. A Rinnai RE180iN review: the flow rate is real, the venting is the bill delivers 4.2 GPM at the same 70 °F rise where the ECO 24 manages 2.3, for roughly three times the purchase price and a venting bill on top. If you already have a gas line, gas wins on capacity in any cold climate and it is not close. If you do not, running one costs more than the electrical work. the gas-versus-electric tankless comparison works through the gas-versus-electric decision properly.
Who should not buy this
- Anyone on 100 amp service. The load calculation will fail. Look at the Rheem RTEX-13 review: excellent at the job it is not sold for as a point-of-use unit, or stay with a tank.
- Anyone north of roughly the 40th parallel wanting whole-home coverage. 2.3 GPM in January is one fixture. Size up, or go gas.
- Anyone planning to fit it themselves. The warranty that makes this unit attractive requires professional installation with documentation.
- Anyone replacing a gas tank. You would be abandoning a gas line and paying for a panel upgrade to end up with less hot water. the ten-year cost comparison against a tank has the ten-year numbers.
What works
- 24 kW for around $420 is the most heating capacity per dollar among the electric units in this comparison.
- Genuine self-modulation. The unit draws only the power the current flow demands rather than switching in fixed stages, which is why output temperature stays flat instead of oscillating.
- Lifetime warranty on the exchanger, element and electronics — the longest cover here by a distance, if you meet the conditions.
- 14.3 lb and 3.5 inches deep. It mounts on a stud bay and disappears, which a 40 gallon tank does not.
- Made in the United States, which in practice means parts availability that does not depend on a container ship.
What doesn't
- The 5.8 GPM headline needs about a 28 °F rise to be true. At the 70 °F rise a northern winter delivers, this is a 2.3 GPM heater — one shower.
- 100 amps across three 40 amp double-pole breakers. On a 100 amp service this is a service upgrade first, and that is a five-figure conversation in some areas.
- The lifetime warranty is conditional on professional installation, original ownership and the original address. Self-install and you have bought a one-year warranty.
- 130 °F maximum setpoint, lower than the 140 °F Rheem and Rinnai allow. Fine for domestic use, restrictive if you wanted headroom for a dishwasher without a booster.
- Priced within $5 of the Rheem RTEX-18, which is a straight comparison the listing would rather you did not make.
The verdict
The EcoSmart ECO 24 is a well-built, fairly priced piece of hardware that is routinely bought by people it does not suit, because the two numbers that decide suitability — your incoming water temperature and your panel's spare capacity — appear nowhere on the box.
Get both of those right and it is the best value electric tankless heater at this output. A copper exchanger, real self-modulation, US manufacture, a lifetime warranty and a 3.5 inch deep enclosure for around $420 is a genuinely good offer.
Get either wrong and you have either a heater that disappoints every winter, or a $420 purchase that unlocked a $4,000 electrical project. Do the load calculation first. Everything else about this decision is downstream of it.
We may earn a commission if you buy through our links — here is how we are funded.
Check price on Amazon Opens Amazon in a new tab. Price and availability change — check before you buy.Questions people actually ask
What size breaker does the EcoSmart ECO 24 need?
Three 40 amp double-pole breakers, feeding a total draw of 100 amps at 240 volts. That is the number that decides whether this is a cheap project or an expensive one. A 200 amp panel with genuine spare capacity handles it; a 100 amp service almost never does, because after a range, a dryer and an air handler there is not 100 amps of headroom left. Have an electrician run a load calculation before you buy the heater, not after.
What is the difference between the EcoSmart ECO 24 and the ECO 27?
Three kilowatts and roughly 12% more hot water. The ECO 27 draws 112 amps against 100, needs three 40 amp breakers just the same, and costs about $80 more. If your panel can take 100 amps it can usually take 112, so the ECO 27 is the better buy in a cold climate. In a warm one the extra capacity rarely gets used. Both are the same chassis with different element counts.
Is the EcoSmart ECO 24 enough for a whole house?
It depends entirely on your incoming water temperature, which is a geography question rather than a household size one. In south Florida, at a 35 °F rise, it delivers 4.7 GPM — two showers and a sink at once. In Minnesota in January, at a 70 °F rise, it delivers 2.3 GPM, which is one shower and nothing else. Our tankless sizing calculator does this arithmetic against a regional groundwater dataset.
Is the EcoSmart lifetime warranty real?
It is real and it is genuinely lifetime on the exchanger, element and electronics — but it carries three conditions that void a large share of claims. It applies to the original owner only, at the original installation address only, and requires professional installation with documentation. Move house, sell the unit on, or fit it yourself on a Saturday, and the cover reverts to one year.
EcoSmart ECO 24 or Rheem RTEX-18?
The EcoSmart, on the numbers. They cost within $5 of each other, and the ECO 24 delivers 24 kW against the Rheem's 18 kW — about 33% more hot water for the same money. The RTEX-18 answers back with a simpler electrical install, two 40 amp breakers rather than three, which matters if your panel is tight on physical spaces rather than on amps. Buy the Rheem for the breaker count, the EcoSmart for the output.
Can I install an electric tankless water heater myself?
Physically, the plumbing is straightforward — two 3/4 inch connections and four screws. The electrical side is not. Three 40 amp double-pole breakers, correctly sized conductors for a continuous 100 amp load, and a panel that can carry it are notifiable work in most jurisdictions and a permit item in many. Beyond the safety question, self-installation voids the warranty that is the main reason to choose this unit.