How to Choose an Electric Water Heater

This article briefly describes the core structure of an electric storage water heater, lists key specifications, and provides several tips on how to choose the right device for a specific user’s needs.

Electric Water Heater Components

The main structural element of a water heater is the electric heating element (TЭN), which is responsible for heating the water. It is located directly inside the water tank. The TЭN’s operation depends on the thermostat settings, which maintain water temperature within a range of 35 to 90 °C. When water cools below the set point by 0.5–1 °C, the TЭN automatically turns on and begins reheating the water to the desired level.

A key component is the insulation material. This can be a cylindrical polystyrene sleeve wrapped around the tank or soft mineral wool used to wrap the tank.

Typically, electric storage water heaters have a maximum power output of up to 2 kW, so they do not overload the electrical network. Since water does not heat up instantly, it's important to choose the right balance between tank capacity and TЭN power to ensure a continuous supply of hot water at the desired temperature.

Keep in mind that electricity is relatively expensive in the country, so it's wise to operate the heater in an energy-saving mode—set the TЭN power not to maximum and allow the unit to gradually heat the required volume of water, for example, overnight.

How to Choose the Right Tank Capacity

The tank capacity depends on hot water consumption in the home or apartment. Usage is influenced by the number of water outlets, household size, and number of water-using appliances connected to the hot water system.

Below is a table showing average hot water consumption per person, depending on the intended use.

Water outlet Average consumption (L) Average temperature Consumption at 60 °C (L) Kitchen sink 10–20 50 °C 13–15 Bath 150–180 40 °C 90–100 Shower 30–50 37 °C 15–25 Sink 10–15 37 °C 5–8 Hand wash 2–5 37 °C 1–3

Example calculation:

We assume a desired hot water temperature of 60 °C, which is most energy-efficient for heating. Since the comfortable skin temperature range for water is 37–42 °C, mixing hot water with cold water reduces consumption to achieve the desired temperature.

On average, for a family of three: each person wakes up, takes a shower, has breakfast, and goes to work. If all three members follow this routine, hot water usage would be:

Shower: 20 × 3 = 60 L. Dishwashing: 13 L.

Total: 73 liters of hot water at 60 °C. Therefore, a 80-liter heater would be suitable to meet this demand without long waiting times for reheating.

Standard tank sizes for electric water heaters are: 5, 10, 30, 50, 80, 100, 120 liters. Larger models exist but are intended for use in complex hot water systems serving multiple families or entire apartment blocks.

If household water usage is high (e.g., many children, large dishwashing volume, or a hydromassage bath), it may be beneficial to install two parallel heaters—one in the kitchen and one in the bathroom. Otherwise, there’s a risk of running out of hot water and having to wait for the next heating cycle.

Price vs. Quality in Electric Water Heaters

As noted above, the design of electric water heaters does not differ significantly between manufacturers. Price differences mainly reflect the reliability of components, thickness and thermal conductivity of insulation, durability of tank material, and longevity of the TЭN—the most expensive part of the system.

The most expensive models are German-made. At the lower end are products from Italian and Turkish manufacturers. These often use Chinese TЭNs and tanks, which cannot be clearly judged as good or bad. However, in practice, their long-term reliability has not been proven over years of continuous, maintenance-free operation, unlike original German parts used in brands such as Vaillant.

Additionally, German water heaters tend to have larger dimensions due to thicker insulation. Some manufacturers have achieved such low heat loss that in a switched-off heater, water temperature drops by only 5 °C per day.