The heater has a sleek, compact design and a gunmetal gray finish. On its front panel is a simple dial for selecting the desired water temperature. Both the water inlet and outlet connections come out of the unit at the bottom and required 0.75-inch NPT pipes. You can open the front panel to gain access to the interior of the water heater. Inside the unit, there are different temperature and flow sensors, as well as multistage heating elements. All of these components are governed by a microprocessor that delivers on-demand hot water at the temperature you want.
Unlike gas tankless water heaters, the Stiebel Eltron Tempra 15B does not require venting. It also has seismic-proof construction. For this reason, it is simpler to install than gas-powered tankless heaters and tank-type water heaters. Even then, Stiebel Eltron recommends professional installation to get the electric setup right. The Tempra 15B needs two separate 40-amp breakers and 8-gauge copper wiring.
This water heater requires 240 volts of electricity and has a maximum electric power draw of 1,440 watts. It is more energy-efficient than electric water heaters with tanks, but it uses a lot more electricity than gas-powered water heaters. Unlike the Rinnai RUC98iN, the Tempra 15B carries no Energy Star certification.
While this is a tankless water heater, it can still hold and heat 0.26 gallons of water. However, it takes 0.58 gpm to activate the heating elements. The Tempra 15B can handle incoming water pressure up to 150 psi and only loses 1.45 psi as it cycles the water through its heating units.
Its minimum heating temperature is 80 degrees Fahrenheit; its maximum is 140 degrees. While this is wide temperature range for an indoor, commercial tankless water heater, the flow rates of the Tempra 15B are rather low. Its maximum flow rate is 2.81 gpm at a 35-degree Fahrenheit temperature rise. This flow rate falls to 2.2 gpm for another 10-degree temperature rise. The heater cannot adequately pump hot water to high-flow showerheads and faucets.
The Stiebel Eltron Tempra 15B is a well-featured, small electric tankless water heater with heavy-duty electronics. However, you need a plumber and an electrician to install it, which might require upgrading your home electricity wiring. This unit does not have a sufficiently high flow rate for cold climates.