The average gas consumption in a private house or apartment is usually calculated in order to determine the cost of heating, hot water (DHW) and cooking. This is done even at the stage of building design or before choosing an energy carrier and a boiler unit for comparison with other types of fuel.
There is a simplified technique on how to calculate the maximum and average gas consumption for heating and domestic hot water, and it will be considered in this material. Although it will not be possible to carry out such a calculation with great accuracy, you can find out the order of the numbers for the upcoming payment.
Calculation of gas consumption for heating
Before calculating the consumption of natural gas for heating a house or apartment, you need to find out one important parameter - the heat loss of a residential building. Well, when it is correctly calculated by specialists at the design stage, it will significantly increase the accuracy of your calculations. But in practice, such data is often missing, because few homeowners pay due attention to design.
Tip. If you have such an opportunity, then it is worth ordering the calculation of heat losses in a private design organization. This will help not only to find out the average gas consumption for heating a private house, but also to understand whether it is necessary to warm it.
The heat loss of a building determines the power of the heating system and the boiler itself or a gas convector. Therefore, when choosing a gas boiler for a cottage or when installing an autonomous apartment heating, you have to use the following average methods for determining heat loss and equipment power:
- According to the general quadrature of the building. The essence of the method is that for heating each square meter 100 W of heat is required with a ceiling height of up to 3 m. In this case, for the southern regions they take a specific value of 80 W / m², and in the northern regions the consumption rate can reach 200 W / m².
- By the total volume of heated rooms. Here, from 30 to 40 W are allocated for heating 1 m³, depending on the region of residence.
Note. The presented specific heat consumption is correct when the temperature difference between the street and indoors is about 40 ° C.
It turns out that heating of an area of 100 m² requires about 10-12 kW of heat per hour during severe colds and when the house is located in the middle lane. Accordingly, for a cottage of 150 m², about 15 kW of thermal energy will be required, for 200 m², 20 kW and so on. Now you can calculate what maximum gas flow the gas boiler will show on the coldest days, for which the formula is used:
V = Q / (q x Efficiency / 100), where:
- V is the volumetric flow rate of natural gas per hour, m³;
- Q - the magnitude of heat loss and power of the heating system, kW;
- q - the lowest specific calorific value of natural gas, on average, is 9.2 kW / m³;
- Efficiency - the efficiency of a gas boiler or convector.
Note. The efficiency of natural gas heat generators ranges from 84–96% depending on the design. The simplest non-volatile units have an efficiency of 86–88%, convectors 84–86%, and high-tech condensing boilers up to 96%.
Calculation Example
As an example, it is proposed to take an apartment of 80 m² in the middle zone of the Russian Federation. To heat it in the coldest period, 80 m² x 100 W = 8000 W or 8 kW will be required. It is planned to install a modern condensing boiler using natural gas with an efficiency of 96%. Then the calculation of gas consumption for heating looks like this:
V = 8 / (9.2 x 96/100) = 8 / 9.768 = 0.91 m³ / h
It is easy to calculate how much fuel is needed per day: 0.91 x 24 = 21.84 m³. But to determine the costs of natural gas consumption, you need to know more real figures, for example, its average consumption in an apartment for the entire heating season.Since significant temperature fluctuations occur during this season, it is estimated that the average amount of fuel will be half the maximum.
Then the average daily gas consumption for heating the apartment will be 21.84 m³ / 2 = 10.92 m³. It remains only to multiply this number by the duration of the heating season, in Moscow it lasts 214 days: 10.92 x 214 = 2336.9 m³. Having made a monthly breakdown, it is easy to determine the cost of autonomous heating of the apartment.
To calculate the average gas consumption in the apartment, you can go the other way. First, find out the gas consumption for receiving 1 kW of thermal energy, and then multiply this value by 8 kW. The calculation formula for calculating the volume of fuel per 1 kW of heat is:
v = 1 / (q x Efficiency / 100), where v - this is the desired volume in m³ / h.
Accordingly, 1 / (9.2 x 0.96) = 0.113 m³ / h, and for the whole apartment it will be 0.113 x 8 = 0.905 m³ / h with a small error. Further calculations are carried out in the same way as described above.
Note. The calculation does not take into account the amount of gas consumed by the gas stove and hot water, which will be discussed later.
DHW gas consumption
When water for household needs is heated with the help of gas heat generators - a column or boiler with an indirect heating boiler, then to determine the fuel consumption it is necessary to understand how much water is needed. To do this, you can raise the data prescribed in the documentation and determining the norm for 1 person.
Another option is to turn to practical experience, and it says the following: for a family of 4 people under normal conditions, it is enough to heat 80 liters of water from 10 to 75 ° C once a day. From here, the amount of heat required for heating the water is calculated according to the school formula:
Q = cm Δt, where:
- C is the heat capacity of water, is 4.187 kJ / kg ° C;
- m is the mass flow rate of water, kg;
- Δt - the difference between the initial and final temperature, in the example is 65 ° C.
For the calculation, it is proposed not to convert the volumetric water consumption to mass, to assume that these values are the same. Then the amount of heat will be:
4.187 x 80 x 65 = 21772.4 kJ or 6 kW.
It remains to substitute this value in the first formula, where the efficiency of the gas column or heat generator will be taken into account (here - 96%):
V = 6 / (9.2 x 96/100) = 6 / 8.832 = 0.68 m³ of natural gas once a day will be spent on water heating. For a complete picture, you can also add the consumption of a gas stove for cooking at the rate of 9 m³ of fuel per 1 person living per month.
How to determine the flow of liquefied gas
Home heating, organized using liquefied petroleum (propane or butane) has its own characteristics. Most often, homeowners install special containers - gas tanks, refueling for the entire heating season. Cylinder heating is much less common. But calculating the consumption of liquefied gas for heating a house does not present any particular difficulties.
The same formula is taken, only the specific heat of combustion of the LPG (propane-butane) equal to 46 MJ / kg or 12.8 kW / kg is substituted into it. Please note: the estimated calorific value of fuel refers to the unit mass (kilogram), and at the gas station, the price is considered the volume (liters). The results can be recalculated after, first you need to find out the consumption of liquefied gas by a conventional boiler (efficiency - 88%), heating a house of 80 m² from the previous example:
V = 8 / (12.8 x 88/100) = 8 / 11.264 = 0.71 kg / h.
Knowing that 1 liter of liquefied gas has a mass of 540 g (reference value), it is not difficult to calculate the propane consumption in liters: 0.71 / 0.54 = 1.3 liters. This is 1.3 x 24 = 31.2 liters of gas per day, and 31.2 x 30 = 936 liters per month. Now, taking into account changes in weather conditions, to determine the average consumption of liquefied gas, the resulting figure should be halved: 936/2 = 468 liters per month. Gas consumption for heating for the year will be (31.2 l / 2) x 214 days = 3338.4 l (for Moscow).
How to reduce gas consumption for heating and other needs
In this section, we will talk about commonplace things that many have heard about. But from the banality their importance does not become less.After all, this is a direct way to reduce the amount of energy used, including the high consumption of gas used for heating a private house.
The following measures will significantly reduce consumption:
- To carry out high-quality insulation of the building, preferably from the outside.
- If possible, automate the heating system so that the rooms of the house are well warmed up while people are in them, and in their absence, the standby temperature of 10-15 ° C is maintained.
- Engage the timer for the indirect heating boiler so that the water in it is prepared for a certain time of day.
- Arrange home heating with water underfloor heating.
- To purchase the most economical gas boilers - condensing.
All these measures will bring even more benefits and will reduce gas consumption, if you will save yourself. It may be possible to install automation only partially or not at all, then you will have to manage the system yourself. By the way, modern controllers for boilers have built-in remote control functions via the Internet or a cell phone.