10 Best Electric On Demand Water Heater 2025 in the United States

The Ranein Electric Tankless Water Heater is a compact and efficient choice if you want endless hot water without waiting for a tank to heat up. It uses 18 kW of power at 240 volts and can deliver up to 4.3 gallons of hot water per minute, which is enough for about 2 to 3 water outlets like showers or sinks around your home. Because it heats water only when you need it, it can save about 60% on heating costs compared to traditional tank water heaters. Its thermal efficiency is high, reaching 99%, so very little energy is wasted. The temperature can be easily adjusted with the LED display, from 86°F to 131°F, letting you set a comfortable level precisely. The unit is relatively small, measuring just under 14 by 19 inches, which means it won’t take up much space and can be wall-mounted in various places. For safety, it includes protections against leaks, overheating, and dampness, and has passed strict quality tests.

The main considerations are that it requires a dedicated 240V power supply with specific circuit breakers and is best for smaller households or limited hot water use points due to its flow rate. If you have a large family or need hot water at many outlets simultaneously, this model might not keep up. Also, installation needs to meet the electrical requirements, which could need a professional. This heater suits anyone looking for an energy-saving, space-saving, and easy-to-control water heater for a small to medium-sized home.

The Stiebel Eltron Tempra 20 Plus Tankless Water Heater offers some impressive features that address key needs for an electric-on-demand-water-heater. It has a flow rate of up to 3.79 liters per minute, which should be sufficient for most households. The power rating of 19.2 kW ensures that it can deliver a significant temperature rise, keeping your showers hot even if demand fluctuates. The advanced flow control technology helps maintain a consistent water temperature, providing comfort and preventing interruptions during hot showers.

Energy efficiency is a strong point as well; the unit has auto-modulation and electronic flow control, and a savings monitor helps track energy costs, making it eco-friendly and potentially cost-effective in the long run. It's compact and wall-mountable, saving space without the need for venting, which can be a big advantage for smaller homes or apartments. The installation requires a minimum 125 A electric service, which might necessitate an upgrade for some homes. The digital temperature display and preset buttons make operation straightforward, and the unit runs quietly.

The warranty is robust, offering 7 years against leakage and 3 years for parts, which provides some peace of mind. However, the maximum flow rate of 3.79 liters per minute may not suffice for larger households with multiple simultaneous hot water demands. Additionally, while it is energy-efficient, the initial cost and potential need for electrical upgrades might be a consideration for some users. This unit is best suited for average-sized homes that require a reliable and efficient solution for on-demand hot water.

The Rheem 18kW 240V Tankless Electric Water Heater is a solid option for those looking to efficiently supply hot water on demand. With a flow rate of up to 4.4 gallons per minute (GPM), it can cater to smaller households or applications requiring moderate hot water supply, making it ideal for apartments or homes with limited space.

One of its strengths is the 99.8% energy efficiency, which means it consumes less energy compared to traditional water heaters. This can help save on electricity bills over time. The unit features an external digital thermostatic control with an LED display, allowing users to set temperatures with +/- 1 degree accuracy, which is a handy feature for precise control and comfort. The self-modulating technology adjusts the power based on the demand for hot water, ensuring consistent performance. Additionally, the durable copper immersion heating elements are field-serviceable, which can simplify maintenance and repair.

However, there are some limitations to consider. The maximum flow rate of 4.4 GPM may not be sufficient for larger households or simultaneous high-demand situations, such as running multiple showers at once. Also, while the installation is straightforward with bottom water connections, it may still require professional assistance for optimal setup, especially for those unfamiliar with plumbing. It’s also worth noting that while the product dimensions are compact (14.5 inches wide and 18.25 inches high), its wall-mounted design might not suit every installation preference.