It is important to know
Electricity consumption for water heating depends on four factors:
- The temperature of cold water that enters the boiler;
- Boiler heat loss;
- Water consumption per day;
- Hot water outlet temperature.
If you want to determine how many kW your water heater will wind per day or month, you need to know these numbers.
Are you just going to buy a boiler and want to calculate its electricity consumption? You can use simplified numbers:
- Average temperature of cold water: + 5 ... + 10 degrees;
- Boiler heat loss: 0.008-0.0012 kW per 1 liter of water;
- Water consumption per day: calculate the consumption of hot water per month and divide by 30;
- Average hot water temperature: 60 degrees.
Separately, I would like to note that it is not recommended to heat water below +55 degrees. Because of this, microorganisms can develop in it, an unpleasant odor will appear in the water from the boiler.
Electricity costs for a larger boiler
For a family of 3, an 80 or 100 liter boiler is suitable. At an energy consumption of 2 kW per hour, an 80 liter boiler will bring the water to the desired temperature for approximately 185 minutes (3 hours). During a heating session, such a boiler will consume 6 kW of energy per day or 180 kW per month, which will range from 327 to 448 rubles per month. What should be considered?
Installation diagram of instantaneous water heater.
Thus, it is not difficult to calculate the energy consumption of a storage water heater:
- you need to decide on the amount of hot water that the family consumes daily;
- find out how many kW of energy a boiler of a suitable volume consumes during a heating session (multiply 2 kW / h by the heating time in hours);
- multiply the resulting number by the number of days in a month (by 30).
Consider the following:
- the boiler can consume more or less 2 kW of electricity per hour of operation (depending on the volume of the boiler and the model);
- the amount of energy consumed by the water heater will depend directly on how many switch-ons of the device occur during the day. Accordingly, the above amount of consumed energy can be several times higher if the boiler turns on water heating repeatedly during the day.
A boiler (storage water heater) is a good solution for private houses and apartments, where there is a long-term shutdown of hot water. Its "thermos" device allows to use hot water for another 3-5 hours after heating, while the boiler does not consume additional electricity. What power of instantaneous water heater is suitable?
Instantaneous water heater connection diagram.
A flow-through water heater is suitable for households where there is a short-term, but frequent failure in the supply of hot water. Although the obvious disadvantage of this type of water heater is that the outlet water will be rather warm. But the amount of electricity consumed will be higher than in boilers, therefore, when connecting such a device, a separate cable and an automatic electrical plug may be required. Instantaneous water heaters can be from 3 to 27 kW. Everything again depends on what the warm water will be used for. If a small family plans to wash daily, wash dishes and sometimes take a shower, a device with a power of up to 8 kW will be enough. If we are talking about frequent hand washing, taking baths, you will need a more powerful heater, which, most likely, will not need 220, but 380 volts, and this is an additional cost not only for the installation, but also for the electricity consumed.How much energy does an instantaneous water heater consume? Let's calculate how much the operation of an instantaneous water heater will cost approximately per month. We will make the calculation using the example of the above-mentioned family, which consumes 50 liters of water per day. The average productivity of a 4.5 kW / h instantaneous water heater is 2 liters per minute. The time it will take him to heat the required 50 liters of water is calculated as follows: 50 liters: 2 liters / min = 25 minutes (0.42 hours); 0.42h x 4.5kW / h = 1.89 kW. This is the daily energy consumption for heating water up to 45 ° C. A flow-through water heater consumes approximately 57 kW per month, or in terms of rubles from 104 to 142 rubles.
Magic formula
In order to heat 1 liter of water by 1 degree, you need to spend 1.16 W or 0.0016 kW of electricity. We will need this value for further calculations.
There is a formula for calculating the energy consumption for water heating:
W = 0.0016 x V x (T1 - T2)
- W is the power consumption;
- V is the volume of the required amount of hot water per day;
- T1 is the outlet water temperature;
- T2 - cold water inlet temperature.
But this way you only get the number of kilowatts needed to heat the water. But after all, it cools down over time
The boiler consumption in standby mode is its cost to compensate for heat loss.
Consumption
Water heater
The cost of paying for electricity depends on how much electricity a water heater consumes. There are three types of heating technology and each of the options has its own characteristics:
- Storage water heater. It is a tank of different sizes, with a heating element inside. The water is heated to a certain temperature, after which the heater is turned off. The process is controlled by a special sensor. When the temperature drops below the set one, the heating element turns on again and brings the temperature to the required one. This leads to an overconsumption of electricity, if you do not use heated water in time and do not turn off the device. The range of electric heaters with a heating element is quite extensive.
- Instantaneous water heater. The device does not have a tank. Water moves through the pipes, enters the heater. Passing through it, the water reaches the required temperature. How much such a water heater consumes will depend on the inlet water temperature.
- Indirect water heater. The water in the tank is heated by the heating system. It can be central heating or a gas boiler. Due to the functional features of the boiler, the water in the heater remains hot for a long time, even after the main heat source is turned off. Thanks to the additional thermal insulation system, the volumes consumed by the indirect heating boiler are very small: due to the indirect use of electricity, significant cost savings are noted.
Through calculations and observations, it was found that flow-through devices consume more electricity, since they have more power. But on the other hand, flow systems are switched on periodically, while storage systems are used constantly. The power of a storage-type water heater is different, therefore, they cannot be called completely energy-saving.
Do not spend a lot and choose the right heating device, perhaps if you find out how much energy the boiler consumes per day.
To make calculations, you need to know the following indicators: the capacity of the water heater, the power of the device, the water consumption, the time required to heat the water to the desired temperature and the power consumption of the device in watts.
To read
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There are sample tables that allow you to estimate how much tank volume is required for comfortable use. For example, it is enough for one person to install a water heater with a volume of ten to thirty liters, while the first number is the minimum volume, the last is normal.A family of two needs a fifty liter boiler. A classic family of two adults and two children needs a water heater with a volume of one hundred to one hundred and twenty liters.
Experts recommend on average to count on one person fifty liters of water per day. It is worth noting that the numbers can be much lower or higher. It all depends on the needs for the use of water: cooking, personal hygiene, doing laundry, washing dishes, taking a bath or shower. There are established norms for water consumption per person: about eighty liters per day are needed for washing, about twenty liters for washing dishes, and about one hundred and eighty liters for bathing in the bathroom.
But when buying, not only the displacement is taken into account. Since there is a mixing of cold and hot water, the consumption is less.
How much heat does the boiler lose?
If you are considering a specific boiler model, take a look at its specification, instruction or manual. Heat loss should be indicated there. The manufacturer can indicate them in percent per hour, kilowatts per hour for the full volume, percent per day and kilowatts per day for the entire capacity.
If heat loss is indicated as a percentage per hour, follow this formula:
W1 = W x (P x 24 +100) / 100
When heat losses are indicated as a percentage per day, the formula is as follows:
W1 = W x (P + 100) / 100
With heat loss in kilowatts per hour:
W1 = P x 24 + W
If heat losses are indicated in kilowatts per day:
W1 = W + P
In all the above formulas:
- W is the amount of electricity. needed for heating water;
- P - heat loss in kilowatts or percent;
- W1 is the amount of electricity in kilowatts. Which is consumed by the boiler per day.
Types of water heaters
Water heaters are of the following types:
- Flowing. The design of the water heater is a plastic case with a built-in heating coil, which is attached to the faucet. The water passing through the spiral warms up to 45-50 degrees. The higher the speed of the water, the lower its temperature. This model is indispensable in the country, in the village or in garden houses.
- Cumulative. The boiler has a storage tank with a built-in spiral. When the water cools down, the temperature sensor is triggered automatically and turns on the heating function. Inside the boiler has layers of insulation that prevent water from cooling. The advantages are obvious: the water is heated around the clock. This type of equipment is suitable for families with children, as well as for the elderly.
If we consider energy consumption, then the flow-through and storage device consume approximately the same amount of energy per day.
The fact is that the flow-through one heats up the water as it is used, and the boiler maintains the set temperature all the time. Therefore, voltage surges in the network (you can notice how the meter quickly winds the disk) will be very noticeable when using an instantaneous water heater.
A boiler that generates heat from an existing heating system is called an indirect heating device. More on this here:
Example of calculating the consumption of a boiler
Let's say there is a boiler with heat loss of 0.5% per hour, and a family needs 200 liters of water per day. Cold water temperature +10, and hot +55 degrees. Hence we have:
- V = 200;
- T1 = 55;
- T2 = 10.
Let's substitute these values in the first formula:
W = 0.0016 x 200 x (55 - 10) = 14.4
It turns out that water heating requires 14.4 kilowatts per day, or 432 per month.
Now let's take into account the heat loss. We already know the number W, and P will equal 0.5. Substitute the values into the formula and get:
W1 = 14.4 x (0.5 x 24 +100) / 100 = 16.128
This means that the average daily consumption of electricity by a water heater is 16.128 kW, and for a month - 483.84 kW.
Calculation for instantaneous water heater
Best of all, a flow-through water heater is suitable for household use; it will not work to take a full, comfortable shower with it.There are very powerful models, but their installation is complicated by a separate line for connection.
Photo 2: How to use a water heater correctly to save energy?
To calculate the consumed electricity, you will need the following data:
- hot water volume (50 liters);
- device power (4 kW);
- productivity (2 l / min).
The widespread statement that flow heaters are more energy-intensive is incorrect.
Boiler calculation calculator
We made this calculator to calculate the amount of electricity required to heat the volume of water you need to the required temperature. We did not take into account heat losses, they are different for each manufacturer and model.
In this publication, we tried to tell in detail how much electricity a boiler consumes per month and show how you can calculate this number. You also learned about ways to reduce the energy consumption of the boiler.
In the comments, you can leave your question or share your experience. Don't forget to share the post on social media
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