10 Best Compact Tankless Electric Hot Water Heaters 2026 in the United States

The EcoSmart ECO 18 is a compact electric tankless water heater designed for residential use in moderate climates where incoming water temperatures are around 62°F or higher. It offers a power rating of 18 kilowatts at 240 volts, which is quite strong for its size (14" x 17" x 3.5") and enables it to provide a maximum flow rate of about 3.5 gallons per minute. This means it can comfortably supply hot water for one or two fixtures simultaneously, such as a bathroom sink and a shower, but might not be enough for larger households needing multiple hot water sources at once.

One of its convenient features is the digital temperature control with 1-degree increments, allowing precise adjustments for comfort. The patented self-modulating technology helps maintain energy efficiency at an impressive 99.8%, which can help reduce electricity costs compared to traditional water heaters. Installation is relatively straightforward due to its compact design, though it requires a 240-volt electrical connection and is best suited for homes with compatible wiring. The unit comes with a lifetime warranty on electronics, exchanger, and heating element, which offers good peace of mind, although the warranty does not cover labor costs or incidental damages.

A drawback is that it’s optimized for warmer incoming water and may struggle in colder climates without additional units or pre-heating, limiting its versatility. The EcoSmart ECO 18 serves as a solid choice for small households or point-of-use scenarios looking for energy-efficient, on-demand hot water in a compact form.

The EcoSmart ECO 27 is a compact, wall-mounted electric tankless water heater that stands out for its high power rating of 27 kW, which allows it to deliver a maximum flow rate of about 6.6 gallons per minute. This means it can supply enough hot water for multiple bathroom fixtures simultaneously in small to medium homes, making it suitable if you want a reliable flow without a bulky tank. It uses 240 volts on a single phase and offers digital temperature control with an easy-to-read LED display, so adjusting hot water temperature up to 120°F is straightforward. The heater is quite space-efficient with dimensions of 17 by 17 by 3.5 inches and weighs just under 11 pounds, which makes installation feasible in tight spots, especially compared to traditional tank water heaters. Energy efficiency is a strong point here; as a tankless unit, it heats water on demand, helping reduce energy waste and utility bills. EcoSmart backs this model with a limited lifetime warranty on key electronic components and heating elements, though the warranty doesn’t cover labor or incidental costs and requires proper registration to remain valid.

One limitation is that the maximum temperature is capped at 120°F, which might be lower than some users expect for specific needs. Also, while the flow rate is good for many households, it might be insufficient for larger homes with higher simultaneous hot water demands. The EcoSmart ECO 27 represents a smart choice if you want compact size, energy-efficient electric heating, and moderate hot water flow, but it may not be the best fit if you need very high temperature settings or serve a larger family with heavy water usage.

The ThermoMate 11kW Electric Tankless Water Heater is a compact, wall-mounted unit designed to deliver instant hot water on demand. It offers a flow rate of about 2.15 gallons per minute with a 35°F temperature rise, which is suitable for low-flow applications like a single bathroom sink, small office break room, or similar points of use. Its maximum flow rate of 2.7 GPM means it won’t support multiple or high-demand fixtures simultaneously but shines where space is limited and continuous hot water is needed.

This model runs on 208 to 240 volts and requires a substantial 46-amp power supply, demanding a 60-amp breaker setup (two double-pole 30-amp breakers). Installation might be more involved than simpler heaters, so some electrical know-how or professional help is recommended. The heater uses self-modulating technology to adjust energy use based on water flow, achieving about 99% energy efficiency, which can cut water heating costs by up to 60% compared to traditional tank heaters.

Durability is a strong point here. The heater's alloy metal housing and separated heating element design help prevent scale and corrosion, reducing maintenance needs and enhancing longevity. Safety features include ETL certification, overheating protection, and automatic shutoff if no water is detected, which adds peace of mind. At roughly 12 by 15 inches and weighing 14.3 pounds, it is fairly compact and easy to fit into tight spaces, ideal for users looking to save floor space. However, it is intended for indoor use only and is best suited for low-demand, point-of-use scenarios rather than whole-home installation. The ThermoMate ET110 is a reliable, energy-efficient choice for users needing consistent instant hot water in compact settings, provided the electrical requirements match your setup. Its limitations in flow rate and installation complexity mean it’s less suitable for larger households or multi-fixture demands.