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Saving on water heating: an electric boiler or a gas water heater?

A simple household question: how much does it cost to take a hot shower for, say, 10 minutes? In 10 minutes, depending on the water pressure, your system can consume from 60 to 100 liters of water. To simplify the calculations, let's assume that you splash as much as 100 liters on yourself.

You have an electric boiler in your home for preparing and storing hot water, or, as a second option, you have a gas water heater that prepares hot water on the fly. So the logical question is, amid rising energy prices, which is more profitable to use?

Let's count!

For domestic use, water at 38-40°C is usually sufficient. However, in the case of an electric water heater, it is important to keep the water temperature at least 55°C to avoid the development of Legionella bacteria, which can cause water odors and other health problems. Legionella grows at temperatures between 20°C and 45°C, so regularly heating the water to 55°C or higher helps prevent its growth. Accordingly, a gas flow-through column can only be set to a heating temperature of 40°C.

Now let's make a comparison taking into account current gas and electricity prices.

Electric boiler:

To heat 100 liters of water from 10°C to 55°C, we determine the amount of heat required, which can be calculated using the formula:

Q=m⋅c⋅ΔT

де:

• m is the mass of water in kilograms (for water, 1 liter = 1 kg),
• c is the specific heat capacity of water (approximately 4.186 kJ/kg-°C),
• ΔT - temperature change.

Let's substitute the values:

 Q=100⋅4.186⋅45=18837кДж

1 kWh is equal to 3600 kJ, therefore: Q = 18837 kJ/3600≈5.23 kWh

The cost of heating: 5.23 kWh × 4.32 UAH = 22.58 UAH

Gas stove:

It takes approximately 0.41 m to heat 100 liters of water from 10°C to 40°C.³ gas. We find this by calculating the amount of heat required, just like for an electric boiler:

Q=m⋅c⋅ΔT=12558 кДж

If the efficiency of the gas column is 90% and the energy value of gas is 34 MJ/m³ (34000 kJ/m³), we get the following values:

Q_{потрібне} =12558 кДж / 0.90=13953.33  кДж

V_газу =13953.33 кДж / 34000 кДж/м3 ≈ 0.41  м³

The cost of heating, based on the current gas tariff plus the cost of its transportation, is obtained: 0.41 м³×11 грн/м³ = 4.51 грн

Conclusions:

Parameter.	Electric boiler	Gas stove
Consumption for heating 100 liters of water	5,23 кВт	0,41 м куб
Cost of heating	22,58 грн	4,51 грн

Thus, taking a 10-minute shower with a gas heater is much more economical than with an electric boiler:

• Electric boiler: 22.58 грн
• Gas stove: 4.51 грн

The choice between an electric water heater and a gas water heater depends on your priorities: convenience and stability or efficiency. Either way, you now have the information to make an informed decision.