Ecosmart US EcoSmart ECOS 18 Tankless vs Ecosmart US EcoSmart ECOS 27 Tankless (2026): Key Differences
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Choosing between the ecosmart us ecosmart ecos 18 tankless vs ecosmart ecos 27 tankless depends on your hot water needs. Both units are electric, share identical dimensions, and offer 96% thermal efficiency. They both use self-modulating technology to maintain temperature within one degree. The main difference lies in power output. The ECOS 18 delivers 18 kW, while the ECOS 27 provides 27 kW. This wattage gap directly impacts flow rates, determining how many fixtures you can serve simultaneously.
Key differences
| Aspect | EcoSmart ECOS 18 Electric Tankless | EcoSmart 27 kW Electric Tankless Water Heater |
|---|---|---|
| Wattage | 18 kW | 27 kW |
| Flow Rate | 1.8 to 4.3 GPM | 2.7 to 6.6 GPM |
| Weight | 9.3 pounds | 10.9 pounds |
| Recommended Use | Bathroom or small sink | Bathroom, small sink, or breakroom |
Which one should you choose?
Choose EcoSmart ECOS 18 Electric Tankless if
- You need hot water for a single bathroom or point-of-use sink.
- Your electrical panel has limited capacity, as the 18 kW model draws less current.
- You prefer a lighter unit that is easier to mount on the wall.
Choose EcoSmart 27 kW Electric Tankless Water Heater if
- You require higher flow rates for multiple fixtures or a larger bathroom.
- You need more hot water volume for an office breakroom or kitchen sink.
- You want greater flexibility with inlet water temperature variations.
Verdict: The ECOS 18 is sufficient for low-flow applications like a single bathroom. The ECOS 27 is better if you need higher volume or serve multiple points of use. Select the model that matches your maximum simultaneous hot water demand.
ECOS 18 vs ECOS 27 Comparison
Power output
The EcoSmart ECOS 18 Electric Tankless delivers 18 kW of power at 240 volts. This model draws 75 amps to heat water on demand. The EcoSmart 27 kW Electric Tankless Water Heater offers higher capacity with 27 kW at the same 240 volts. It requires a higher electrical draw of 112.5 amps. You need a stronger electrical circuit for the larger unit. The 27 kW model provides more heating energy per minute. Choose the 18 kW version if your electrical panel has limited capacity. Select the 27 kW model if you have the necessary amperage available for higher output.
Flow rate
Flow rate determines how much hot water you get per minute. The ECOS 18 provides between 1.8 and 4.3 gallons-per-minute. This depends on your inlet water temperature. The ECOS 27 offers a higher range of 2.7 to 6.6 gallons-per-minute. This also varies based on inlet water temperature. The 27 kW unit delivers more water simultaneously. You can run more fixtures at once with the larger model. The 18 kW unit is better for single-point use. It suits a small sink or a single bathroom. The 27 kW model handles higher demand scenarios.
Dimensions
Both units share the exact same physical footprint. The ECOS 18 measures 19 inches in height, 4.25 inches in width, and 9.25 inches in length. The ECOS 27 also measures 19 x 4.25 x 9.25 inches. They are both white and designed for wall mounting. The 27 kW model is slightly heavier at 10.9 pounds. The 18 kW model weighs 9.3 pounds. The weight difference is minimal for installation purposes. You can mount either unit in the same space. Both are 90% smaller than traditional tank heaters. This compact design saves space in your utility area.
Temperature control
Both heaters use patented self-modulating technology. This system continuously monitors water temperature and controls flow rates. The ECOS 18 maintains performance within one degree of your selected temperature. The ECOS 27 also keeps temperature within one degree of the setting. Both models provide consistent hot water when you need it. Neither unit runs out of hot water during use. The self-modulating feature ensures efficiency by only heating water when called. You get precise temperature control with either model. The technology prevents sudden temperature fluctuations during use.
Ideal applications
The ECOS 18 is ideal for a bathroom, small sink, or point-of-use applications. It works well for low-flow needs. The ECOS 27 is suitable for a bathroom, small sink, office breakroom, or other point-of-use areas. It also handles low-flow applications. The 27 kW model is better for slightly larger demands like a breakroom. The 18 kW model is sufficient for standard residential bathrooms. Both are electric and do not require venting. You can install them at the point of use. Choose based on your specific water usage requirements.
Which tankless water heater fits you
You need hot water for a single bathroom
The ECOS 18 provides 1.8 to 4.3 gallons per minute. This flow rate suits a single bathroom sink and shower. Its 18 kW power handles low-flow needs efficiently. The compact 19-inch height saves space on your wall. You get consistent temperature control within one degree for reliable daily use.
You want higher flow for multiple fixtures
The ECOS 27 delivers 2.7 to 6.6 gallons per minute. This higher output supports bathrooms, small sinks, or office breakrooms. The 27 kW power ensures better performance with colder inlet water. You maintain precise temperature control within one degree. This unit handles higher demand without compromising hot water consistency.
You need a compact point-of-use solution
Both units share identical dimensions of 19 by 4.25 by 9.25 inches. The ECOS 18 weighs slightly less at 9.3 pounds. This lighter weight makes wall mounting easier. Its 18 kW capacity is sufficient for point-of-use applications. You save 90% space compared to traditional tank heaters while getting endless hot water.
The products compared
EcoSmart ECOS 18 Electric Tankless
Best for: single bathroom or point-of-use setups
- Fuel Type
- Electric
- Flow Rate
- 1.8 to 4.3 GPM
- Wattage
- 18 kW
- Voltage
- 240 V
- Temperature Control
- within 1 degree
- Dimensions
- 19 x 4.25 x 9.25 inches
View on Amazon: EcoSmart ECOS 18 Electric Tankless Affiliate link
The EcoSmart ECOS 18 is an 18 kW electric tankless water heater designed for point-of-use or single bathroom applications. It delivers 1.8 to 4.3 gallons per minute depending on inlet temperature. Its compact 19 x 4.25 x 9.25 inch footprint saves space. The unit maintains temperature within 1 degree of your selection. It is ideal for low-flow needs where a smaller unit fits better than the 27 kW model.
Pros
- 18 kW power output for efficient on-demand heating
- Compact dimensions of 19 x 4.25 x 9.25 inches
- Temperature control within 1 degree of selected setting
- Up to 96% thermal energy efficiency
Cons
- Lower flow rate of 1.8 to 4.3 GPM compared to higher kW models
- Limited warranty of one year for parts
- Requires 75 Amp circuit capacity
Good fit if
- You need a heater for a single bathroom or small sink
- You have limited space for installation
- You prefer electric point-of-use solutions
Skip if
- You need to supply hot water for multiple fixtures simultaneously
- You require a higher flow rate than 4.3 GPM
- You are looking for a longer parts warranty
Verdict: EcoSmart ECOS 18 Electric Water Heater is a compact, efficient choice for single-fixture applications. It suits you if space is tight and your hot water demand is low.
EcoSmart 27 kW Electric Tankless Water Heater
Best for: single bathroom or small sink point-of-use
- Fuel Type
- Electric
- Flow Rate
- 2.7 to 6.6 GPM
- Wattage
- 27 kW
- Voltage
- 240 V
- Temperature Control
- within 1 degree
- Dimensions
- 19 x 4.25 x 9.25 inches
View on Amazon: EcoSmart 27 kW Electric Tankless Water Heater Affiliate link
The EcoSmart ECOS 27 is a 27 kW electric tankless water heater designed for point-of-use applications. It delivers a flow rate between 2.7 and 6.6 gallons per minute, depending on inlet water temperature. The unit maintains water temperature within 1 degree of your selection. It measures 19 by 4.25 by 9.25 inches and weighs 10.9 pounds. This compact model suits small sinks, bathrooms, or office breakrooms where space is limited.
Pros
- 27 kW power output for consistent hot water
- Maintains temperature within 1 degree of setting
- Compact dimensions of 19 x 4.25 x 9.25 inches
- 96% thermal energy efficiency
Cons
- Limited to 240 Volts electrical connection
- Lower flow rate compared to higher-kilowatt models
- Only one year parts warranty
Good fit if
- You need hot water for a single bathroom or small sink
- You have a 240 Volt electrical circuit available
- You want a compact unit for point-of-use installation
Skip if
- You require high flow rates for multiple simultaneous fixtures
- You only have a 120 Volt electrical outlet
- You need a unit with a longer parts warranty
Verdict: EcoSmart ECOS 27 Electric Water Heater fits users needing reliable hot water for low-flow applications like a bathroom or small sink. Its compact size and precise temperature control make it suitable for tight spaces.
Specifications side by side
| Spec | EcoSmart ECOS 18 Electric Tankless | EcoSmart 27 kW Electric Tankless Water Heater |
|---|---|---|
| Fuel Type | Electric | Electric |
| Flow Rate | 1.8 to 4.3 GPM | 2.7 to 6.6 GPM |
| Wattage | 18 kW | 27 kW |
| Voltage | 240 V | 240 V |
| Temperature Control | within 1 degree | within 1 degree |
| Dimensions | 19 x 4.25 x 9.25 inches | 19 x 4.25 x 9.25 inches |
| Weight | 9.3 pounds | 10.9 pounds |
| Color | White | White |
| Model | ECOS 18 | ECOS 27 |
Frequently asked questions
Does the ECOS 27 use more electricity than the ECOS 18?
Yes. The ECOS 27 draws more current because it has higher wattage. It operates at 27 kW compared to the ECOS 18's 18 kW. Both units run on 240-volt power. The higher wattage allows the ECOS 27 to heat water faster or handle slightly higher flow rates.
Can I install either unit in a small closet?
Yes. Both heaters share the same compact footprint. Each measures 9.25 inches in width and length, with a height of 19 inches. The ECOS 18 weighs 9.3 pounds, while the ECOS 27 is slightly heavier at 10.9 pounds. Their identical dimensions make them suitable for tight spaces.
Is the ECOS 18 better for a single bathroom?
It is often the preferred choice for this setup. The ECOS 18 delivers 1.8 to 4.3 gallons per minute. This flow rate is sufficient for one sink and shower. Its 18 kW output matches low-demand needs efficiently without over-sizing the electrical circuit.
Do both models have digital temperature control?
Yes. Both units use self-modulating technology to adjust heating elements. This system maintains water temperature within one degree of your setting. You get precise control over the output temperature on both the ECOS 18 and ECOS 27 models.
What is the weight difference between the two heaters?
The ECOS 27 is heavier by 1.6 pounds. The ECOS 18 weighs 9.3 pounds, while the ECOS 27 weighs 10.9 pounds. This slight difference comes from the additional heating components in the 27 kW model. Both are still lightweight enough for standard wall mounting.
Are the physical dimensions identical for installation purposes?
Yes. Both the ECOS 18 and ECOS 27 have identical external measurements. They are both 9.25 inches wide, 9.25 inches long, and 19 inches tall. You can use the same mounting template or space for either unit without modifying your installation area.