What should be the volume of the tank for an electric boiler

The best way to avoid paying extra for electricity when using a boiler is to choose the right water heater. And you should start with the volume of the tank. Boilers are not accidentally called storage water heaters. Unlike flow devices, they heat the liquid inside a closed tank, where it is stored until the valve of the hot water faucet or shower is opened.

Typical consumption of hot water is approximately 20 - 40 liters per person per day. And electric boilers can have a tank volume from 5 to 500 liters. Where does such a spread in characteristics come from? The fact is that each of the boilers is designed for its own operating conditions.

  • Small boilers with a volume of up to 15 liters are usually installed in the kitchen, office and other places where the need for hot water is relatively small.
  • Boilers with a volume of up to 50 liters - completely cover the needs of one average person in hot water for washing, showering and washing dishes.
  • Boilers with a volume of 80 - 100 liters are the most common water heaters, combining a decent volume (which is enough for a couple or a family of three) and not too large sizes, allowing you to install the boiler in a bathroom or bathroom in such a way that it does not take up too much space.
  • Boilers for 150 - 200 liters of water are large heaters that make sense to install in private houses where 4 - 5 residents live.
Comparison of the sizes of the same type of electric boilers of different volumes.

If you buy too small a boiler, its volume will not be enough for the needs of the family, and the heating element will turn on too often, winding the counter. A water heater that is too large will simply heat water in vain, consuming excess electricity, and spending too much time heating the liquid to the desired temperature. Therefore, the correct selection of a boiler according to the volume of the tank is perhaps the most important aspect when choosing a device for heating water. But it should also be noted that different families approach the use of hot water in different ways, and our recommendations (based on statistics and observations of boiler manufacturers) may not fully correspond to your specific needs and habits.

Separately, one should dwell on boilers with two tanks. Thanks to the presence of two containers, some water can be quickly heated for urgent needs (for example, to be able to rinse your hands or wash a couple of dishes after dinner) even when the main volume of hot water has already been used for a shower or bath. But it should be noted that double tank boilers are more expensive than traditional water heaters.

Popular two-tank boilers

Influence of the shape of the boiler on electricity consumption

As you can see from a glance at the catalog of water heaters, manufacturers offer boilers with tanks of various shapes. The cylindrical shape of the storage tank is considered a classic. The round tank has the smallest surface area (reduces heat loss) and the shortest possible length of welds (increases reliability and increases the service life of the tank). But in practice, it is sometimes more profitable to buy a rectangular or flat boiler in order to save space and install the device closer to the point of water analysis ( sink or bathtub). In addition, rectangular household appliances visually look better next to the kitchen or bathroom furniture. For similar purposes (that is, to save space or rational use of the space of the room), storage water heaters are produced designed for horizontal installation.

But if the shape of the tank itself has almost no effect on the efficiency of the boiler, then the thickness of the heat-insulating layer greatly affects the consumption of electricity. For any storage boiler, the space between the outer shell (body) and the tank is filled with an effective heat-insulating material - polyurethane foam. It creates the effect of a thermos, not allowing the storage tank to cool down quickly. For most boilers, the thermal insulation layer has a thickness of 2.0 - 2.5 cm. But sometimes manufacturers, for the sake of compactness, slightly reduce it. This occurs, as a rule, in flat and narrow water heaters, when engineers' attempts to reduce dimensions lead at the same time to a decrease in the energy efficiency of devices. But boilers with rectangular cases, on the contrary, usually have a thicker layer of thermal insulation, since the shape of the case allows more polyurethane foam to be squeezed inside ( Atlantic, for example, claims that its rectangular boilers from the Atlantic Steatite Cube series have daily heat losses of 30% - 45 % less than that of cylindrical water heaters of the same brand, precisely due to the increased thickness of thermal insulation).

Technical solutions to reduce electricity consumption

In the context of electricity consumption, the most important parameter of a boiler is the power of its heating element. Most storage water heaters have a capacity of 1 kW to 2.5 kW. More powerful models consume more electricity per unit of time, but heat water faster. Less powerful - on the contrary: they do not spin the counter so vigorously, but remain on longer. Therefore, according to the laws of physics, “powerful” and “weak” boilers spend approximately the same amount of electricity to heat the same volume of water.

But manufacturers of household appliances have come up with several ways to reduce electricity consumption by optimizing the operation of the boiler. Some heaters have two or even three heating elements. The meaning of such a solution is usually to ensure a more uniform heating of the water, thereby reducing the operating time of the heating elements. But the “intelligent” control of the water heater seems to be more effective. For example, equipment with programmers can be configured in such a way that the device heats water according to a certain schedule and does not waste electricity in vain. And "smart" boilers generally adapt themselves to their owners. For a week or two, they study your rhythm of life and, in a fully automatic mode, create the optimal schedule for heating water. Such a boiler, for example, will not heat water while you are at work, but it will heat up to the desired temperature exactly by the time you return home. But, of course, any electronic "gadgets" and "smart" automation increase the cost of water heaters.

Water heaters with 3 heaters

"Wet" and "dry" heating elements

But even the most energy-efficient boiler will not work properly if service is not carried out on time. It's about hard water. Even the highest quality and purest tap water contains some dissolved minerals. They are deposited on the "wet" heating element of the boiler in the same way as on the walls of the electric kettle. Even a millimeter layer of scale on the heating element significantly reduces its heat transfer (part of the energy is spent on heating not water, but deposits adhering to the heating element). Therefore, many manufacturers of household appliances began to produce boilers with "dry" heating elements. In the most "advanced" implementations, a "dry" heating element is a set of ceramic elements enclosed in a metal flask, which is in contact with water, giving off heat to it. If a thick and hard “crust” of deposits forms on a conventional “wet” heating element, then only a loose coating is deposited on the bulb of a “dry” heating element, which does not impair heat transfer so much. Therefore, as practice shows, over the years, boilers with "dry" heating elements consume less electricity for heating water, all other things being equal.

Boiler device with "wet" (left) and "dry" (right) heating element.
Water heaters with dry heater

How to determine the energy efficiency of an electric boiler

Electric boilers cannot be called very energy efficient devices ( gas boilers significantly outperform them in this indicator). According to the classification of the European Union of Home Appliance Manufacturers, most of the boilers belong to classes from B to D (we wrote about what these letters mean earlier in the article “From A +++ to G: energy efficiency classes of household appliances”). The difference between devices of classes B and D is quite large - the power consumption can differ by 10% - 15%. Therefore, when buying a boiler, pay attention to the Energy Label stickers, which indicate which class this or that model of heating equipment belongs to.