A true indirect water heater with electric backup is a storage tank heated by a boiler or other primary heat source, with an electric element available as backup. The five listed products are not indirect water heaters: they are small electric point-of-use heaters or immersion heaters. They may suit a sink, bucket, or temporary hot-water task, but they are not substitutes for a whole-home indirect tank. The ThermoMate and other compact units are best for limited faucet use; immersion models are for heating water in a container.
| Product | Best suited for | Important limitation |
|---|---|---|
| ThermoMate 3500W tankless | Small sink hot-water demand | Point-of-use unit, not a storage tank |
| 3000W 110V tankless heater | Low-flow kitchen or bathroom use | Not suitable for showers |
| 2000W immersion heater with LCD thermometer | Heating water in a bucket or container | Requires full immersion before power is connected |
| crazybrace 2000W immersion heater | Portable bucket or small-pool water heating | Use only with water and follow immersion instructions |
| 3kW under-sink tankless heater | One low-flow point of use | Not designed for multiple taps or showers |
ThermoMate 3500W Tankless Water Heater
This model is best for a buyer seeking a compact electric heater for a kitchen or bathroom sink rather than a backup element for an indirect tank. Its listed name specifies 120V, 29.2 amps, 3500W, on-demand operation, and a temperature display. Those details make it the closest match here for a fixed point-of-use hot-water need.
Why it was selected: The listed power and display features are relevant to a buyer comparing small electric heaters. Limitation: The product information provided does not establish storage capacity or compatibility with an indirect tank, so do not treat it as a tank backup.
3000W 110V Tankless Electric Heater
This compact unit is best for a low-flow sink application where an on-demand heater is more appropriate than a storage tank. The listed features include a 3000W output, 110V supply, LED display, and selectable Fahrenheit or Celsius display. The product description states temperature rises of 82°F at 0.3 GPM and 131°F at 0.5 GPM.
Why it was selected: Its stated low-flow performance helps clarify the limits of small electric units. Limitation: The listing says it is not suitable for showers, which commonly require at least 1.8 GPM. It is not an indirect tank or an electric backup element.
2000W Immersion Heater With LCD Thermometer
This portable heater is best for a buyer who needs to warm water in a bucket or similar container, not supply a home’s plumbing. Its listed features include a 2000W element, 304 stainless steel protective cover, and digital LCD thermometer. The product description says it can heat five gallons in a few minutes, while larger volumes may take longer.
Why it was selected: It offers a portable electric way to heat a limited amount of water. Limitation: The instructions say to fully immerse it before connecting power, avoid touching the water while it operates, and not use it continuously for more than three hours.
crazybrace 2000W Portable Immersion Heater
This model is best for portable water heating during camping or for a bucket or small pool, based on its listed use cases. It operates at 110–125V AC and includes a 304 stainless steel guard and LCD thermometer. Its product description says it can heat up to five gallons in a few minutes, with more time needed for larger amounts.
Why it was selected: It is a distinct container-heating option with a temperature-reading feature. Limitation: The listing says to use it only for water and to ensure it is completely submerged before connecting it to power.
3kW Under-Sink Point-of-Use Heater
This heater is best for one low-flow tap where adjustable temperature control is useful. Its listed features include 3kW, 120V plug-in operation, a digital display, a control knob, a 30–55°C temperature range, and safety protections such as overheat, leakage, dry-heating, and over-pressure protection.
Why it was selected: The product description clearly identifies it as a one-point-of-use heater and lists operating limits. Limitation: It is not designed for showers or multiple taps at once; the listing notes that output temperature depends on inlet temperature, flow, and heater capacity.
Buying Guide: Choosing an Indirect Heater With Electric Backup
What should a true indirect water heater include?
Look for a storage tank designed to receive heat from a boiler through a heat exchanger, plus a built-in electric element if electric backup is required. Verify tank capacity, element specifications, electrical requirements, and compatibility with the existing boiler and controls. None of the five products above is described as this type of equipment.
Do you need whole-house hot water or one-point heating?
For whole-house supply, compare indirect storage tanks and their backup-element options with a qualified installer. A small tankless point-of-use unit is intended for limited flow at a faucet. An immersion heater warms water in a container and does not supply plumbing fixtures.
How should electrical needs affect the choice?
Check voltage, wattage, circuit requirements, and installation instructions before buying. The listed tankless options are 110V or 120V models, while the immersion units specify a grounded 120V outlet. These product details alone do not confirm whether a particular household circuit is suitable.
Frequently Asked Questions
Is a tankless point-of-use heater an indirect water heater?
No. A point-of-use tankless heater warms water as it flows through the unit. An indirect heater stores water in a tank and receives heat from a separate primary source.
Can an immersion heater act as an electric backup for an indirect tank?
No. The listed immersion heaters are designed to be submerged in a separate container of water. The provided information does not identify them as tank elements or approve them for installation in a storage tank.
Which listed product is best for a single sink?
The ThermoMate or the 3kW under-sink model may fit a low-flow, single-sink use case. Compare their stated specifications and installation requirements; neither is a whole-home indirect system.
Can these compact heaters supply a shower?
The 3000W and 3kW product descriptions state that they are not suitable for showers. The other listings do not establish shower performance, so do not assume they can meet that demand.
What should buyers do if they need a real electric backup tank?
Shop for an indirect storage tank specifically described with an electric backup element, then confirm its capacity and electrical and boiler compatibility with a qualified installer.