Competent calculation of the power of the air conditioner is the key to effective, uninterrupted operation and durability of climate technology. The choice of performance is based on the overall dimensions of the room and related factors contributing to the accumulation of thermal radiation.
Accounting for all the parameters and nuances of operation allows you to provide the optimal power reserve, but do not overpay the splitsystem for overperformance.
But how to perform the necessary calculations? We will consider this question in detail in our article. In addition to the two methods of calculating power, we will focus on other important criteria that affect the choice of air conditioner.
The content of the article:
 What do the power values in the documentation mean?
 BTU value and label interpretation
 Power Consumption and Energy Efficiency Assessment

Methods of selfcalculation of power
 Option # 1  the choice of air conditioning on the service area
 Option # 2  use heat calculation

Step by step calculations of equipment power
 Calculation of power for a particular room
 Consideration of special operating conditions

Additional criteria for selecting air conditioning
 Criterion # 1  air conditioner view
 Criterion # 2  principle of operation
 Criterion # 3  features and brand
 Conclusions and useful video on the topic
What do the power values in the documentation mean?
The technical documentation for air conditioners indicates two or three types of power. The indicators characterize different operating parameters: cooling and heating performance, as well as electric power consumed by the splitsystem.
The variation of the indicators can be misleading. In heating appliances, for example, a boiler or a radiator, the heat dissipation power corresponds to the energy consumed. For air conditioning, these parameters are different.
Split complex, unlike a heater, does not directly convert electricity, but uses it to operate a heat pump. The latter is able to transfer heat energy much more than the electric power expended.
An example of the display of power characteristics in the passport to the air conditioner Lennox GHM09, operating in two modes: cooling and heating
Refrigeration capacity  the main technical characteristic that determines the ability of the air conditioner to remove heat outside the building. Power consumption is interesting in terms of the selection of supply cables and cost planning
Cooling capacity is indicated in kW, the range of values of household equipment  28 kW. In addition, many manufacturers in the technical descriptions use the British label  BTU (BTU).
The cooling capacity of the split should be adapted to the conditions of service. Otherwise, the normalization of the microclimate to a predetermined temperature will become an overwhelming task for the air conditioner and will disable the equipment.
Two scenarios are possible:
 low productivity  work of the unit on the verge of possibilities;
 excess power  an increase in the number of on / off, which is detrimental to the motor.
The ability to heat the room characterizes the thermal performance of the split. The heat output is always slightly higher than the cooling capacity. The difference between the indicators is the ratio of heat loss on the route of freon pumping in cooling and heating modes.
The heat output is especially relevant if the air conditioner is planned to be used as an interseasonal heat source. Split complex at times more efficiently electric heater. On the peculiarities of the work of the split system for heat, we talked here.
Per 1 kW of electricity consumed modern air conditioners produce about 3.65.5 kW of heat. This volume is enough to heat a living area of 3655 square meters, respectively.
BTU value and label interpretation
BTU / BTU is a British thermal unit for measuring heat energy. The value determines the amount of heat spent on heating one pound of water per 1 ° of Pharyngate.
This unit expresses the cooling capacity of climate technology and is often present in product labeling.
Ratio between watt and btu / h:
 1 Btu / h ≈ 0.2931 W, for convenience, calculations use 0.3 W;
 1 kW ≈ 3412 BTU / h.
Air conditioning  an American invention, which applies the Western system of measures. For the practicality and clarity of the display, the cooling capacity was decided to standardize and express in round numbers, for example: 7000 BTU / h, 9000 BTU / h, etc.
Split models have corresponding names: “seven”, “nine”, etc. So, the LG GO7ANT conditioner belongs to lowpower units  "sevens". Its performance is 2.1 kW
Understanding the digital designation in marking equipment, it will be possible to determine approximately which space the air conditioner is designed for.
Power Consumption and Energy Efficiency Assessment
As noted above, in addition to cooling and heating capacity, the power consumption is indicated in the passport of the split system. The value determines the power consumption. We recommend to read the rules calculation of electricity consumption and ways to save it.
However, the coefficient and energy efficiency class are more informative.
EER and COP  indicators of energy efficiency of the air conditioner in the mode of cooling and heating, respectively. The value is calculated by dividing the cooling or heat output by the power consumption
Essentially, the coefficients EER and COP show the amount of cold / heat produced while consuming 1 kW of electrical power. The greater their numerical value, the higher the efficiency of the climate system and the lower the level of energy consumption.
That is, when EER = 2.5 air conditioner at maximum cooling power consumes electricity Q / 2.5. Multiplying the result for the period of work, you can find out the daily power consumption.
Based on the EER, splits are classified into energy efficiency classes. The category “A” includes the most economical copies, the “G” group consists of air conditioners with the highest electricity consumption.
There are three additional premium class that characterize energysaving climate equipment. A worthy representative of the group A +++  splitcomplex MSZLN60VGR from Mitsubishi Electric
Methods of selfcalculation of power
There are several ways to calculate the performance of splits. The simplest, but not reliable enough  the calculation of the area. A more accurate one is the heat engineering method, which takes into account the design features of the room and the total thermal inflows.
Option # 1  the choice of air conditioning on the service area
It is possible to determine the approximate capacity of the unit without mathematical calculations, appealing with a practical evaluation criterion  the area of the room.
The average cooling capacity of the split is 1 kW per 10 square meters of the serving room. This norm is relevant for residential premises with a ceiling height of 2.53 m.
Thus, when calculating the power of the air conditioner, the service area must be divided by 10. For example, a model with a capacity of 2.2 kW is suitable for a room of 22 square meters. The obtained value corresponds to the "seven" in the BTU system.
The design capacity is increased by 20% in the following cases:
 the location of the room on the sunny side of the house;
 the presence of panoramic windows;
 placing a large number of office equipment, electrical appliances.
The cooling capacity margin of 20% should be foreseen if there are many people permanently living or working in the room.
When choosing climate technology for spacious rooms of 60 sq. M, industrial or commercial buildings, the direct dependence of the cooling power on the area no longer works.
Due to the impressive dimensions, possible angularity and curvature, the air flows are unevenly distributed. In this case, it is advisable to install multisystem splitcomplexes.
Option # 2  use heat calculation
Thermal calculation is considered more accurate, taking into account the structural and operational features of the building. Next, consider the typical formula used for calculations.
Determining factors:
 room dimensions: area and exact height;
 number of people;
 purpose of the room: gym, active work, rest, etc .;
 heat sources, household / office equipment;
 the presence of insulated facades and roofs.
The main emphasis in assessing the power of the air conditioner is on the total heat gain.
The proposed method of thermal calculation is applicable for office premises, separate rooms of private houses and apartments in capital buildings. Area restrictions  70 sq.m.
The greater the heat flow, the higher should be the cooling capacity of the split.
Typical formula:
Q = Q1 + Q2 + Q3,
Where: Q  total cooling capacity; Q1  heat gains from structural elements of the room; Q2  heat leakage from people; Q3  heat dissipation from technology.
Step # 1  Q1 Calculation
The heat excess of the room is determined as follows:
Q1 = V * g,
Where: V  the volume of the room served, calculated by the product of square footage and the height of the ceilings; g  calculated heat transfer coefficient.
The value of g depends on the orientation of the windows and the level of natural light in the room:
 40  sunny side, intensive insolation characteristic of the south, southwest, southeast;
 35  moderate illumination of the east, northwest, west side;
 30  the prevalence of shading during the day is observed in rooms with windows facing north or northeast.
As you can see, for the sunny side there will be the highest heat transfer coefficient.
Step # 2  Q2 Definition
Heat production of people depends on their age and mobility.
For an adult, the following heat emission characteristics are characteristic:
 resting state  80 W;
 light work, moderate load  125 W;
 active activity  170 watts.
When doing hard work and intense sports exercises, heat production reaches 250 watts.
For a more reliable estimate, heat inflows of children under 12 years of age are taken with a coefficient of 0.5, up to 17 years of age  0.75
However, this approach is justified when choosing a splitsystem in children's institutions. Air conditioning is purchased for the future, so for a family, the heat transfer of children should be equated to "adult" indicators.
For an apartment cooling system, the parameter Q2 is determined by the product of the number of residents and the average value of heat generation  about 110 watts.
Step # 3  Calculate Q3
Heat surplus from electrical equipment is calculated by the formula:
Q3 = N * m * i,
Where:
 N  power unit equipment;
 m  the number of household appliances;
 i  the conversion rate of electricity into heat.
In the calculations it is necessary to take into account the frequency of use of technology during the day, taking roundtheclock work per unit.
The energy transfer factors for different equipment are shown in the table. Additional values of heat gain: TV  0.2 kW, copier, computer  0.3 kW, other lighting / household appliances  30% of the rated power consumption
Summing up the total amount of heat leakage, you can determine the power of the air conditioner. It is acceptable to exceed the cooling capacity of the unit by 15% of the calculated indicator or its decrease  by a maximum of 5%.
Step by step calculations of equipment power
To begin with, we will carry out the calculation of the necessary equipment capacity for a specific room of 24 square meters And then we will consider in what situations adjustments are used.
Calculation of power for a particular room
Calculated data to determine the performance of the split:
 room space  24 square meters, ceiling height  2.8 cm;
 room with a standard window facing south;
 the number of residents  2 people;
 equipment appliances: computer, TV, refrigerator (0.3 kW), incandescent lamp (0.1 kW).
Possible simultaneous operation of the listed electrical appliances.
Step 1  determination of heat gains from windows, floors, walls and ceilings.
Q1 = 24 * 2.7 * 40 = 2592 W
The resulting value can be safely rounded to 2.6 kW. In the calculation, the coefficient g = 40 is used, since the room is well lit.
Step 2  calculation of heat gain from people. The heat production of an adult person we take for 110 watts.
Q2 = 2 * 110 = 220 W or 0.22 kW
Step 3  thermal inflows from the equipment are calculated for each type of technology, taking into account the power conversion factor
 computer  0.3 kW;
 TV  0.2 kW;
 electric bulb  90 W (100 W * 0.9);
 the refrigerator  100 W (300 W * 0,3).
Q3 = 300 + 200 + 90 + 100 = 600 W or 0.6 kW
Step 4  Calculation of the cooling capacity of the air conditioner.
Q = 2.6 + 0.22 + 0.6 = 3.42 kW
For comparison, it is possible to carry out an approximate selection of the air conditioner solely on the area without taking into account the number of resident and thermal inflows. For an area of 24 square meters, the estimated cooling capacity should be 2.4 kW, taking into account good illumination  2.4 * 1.2 = 2.88 kW.
According to the initial parameters, it is recommended to select an air conditioner with a capacity in the range of 3.33.9 kW. This value corresponds to the splits of the "twelve"  their performance is 3.53.5 kW
In this situation, the results of calculations by two methods differ. Priority  "thermal" calculation. The cooling capacity of the air conditioner should redeem all possible heat gains.
Consideration of special operating conditions
The technique described above in most cases does not need to be corrected and gives an accurate result.
Special attention deserves:
 the need for regular airing;
 the location of the room on the top floor;
 hot climate of the region;
 large glass area.
Consider all of these cases in more detail.
Fresh air intake
The documentation for splitsystems usually stipulates that operation of the device with windows open is undesirable.
The influx of the external airflow, entering the room, creates an unforeseen thermal load for the climate equipment. The amount of fresh air is not normalized, and it is difficult to predict in advance the optimal power reserve
To maintain a normal microclimate without constantly moving the sash, you can leave the window microventilated or install inlet valve. Both options do not provoke drafts when the front door is closed.
When operating the split in the conditions of gentle airing should be considered:
 In order to compensate for the additional heat load, the indicator Q1 should be increased by 20% when calculating the power of the air conditioner.
 Electricity consumption during the split operation will increase to 15%.
In hot weather, do not rely on the power reserve. With significant heat leakage conditioner will not provide the desired temperature.
Top floor accommodation
In the attic and apartments of the last floors without an attic, the heat of the heated roof is transferred to the inside of the room. The situation is exacerbated by the presence of darkcolored flat roofs.
To compensate for heat leakages from the roof, a cooling capacity margin is provided  when determining the power of the air conditioner, the Q1 value is multiplied by a factor of 1.151.2
The hot climate of the region
One of the rules of safe use of air conditioning is to comply with the permissible temperature difference outside and inside the building. The limit is 10 ° С. For example, if outside the window is 35 ° С, then the recommended temperature in the room is not lower than 25 ° С.
The rated power of the splitcomplexes is indicated taking into account operation in conditions up to 3133 ° C. With an increase of up to 40 ° C or more, the cooling capacity of the unit is not enough to maintain the cherished 1820 ° C.
Given the climate predisposition to hot summer and their own preferences for the level of coolness, the Q1 indicator should additionally be increased by 2030% when calculating.
Large windows in the room
A typical formula assumes that a room has one window of standard dimensions  up to 2 sq.m. Multiple window openings or a panoramic design increases unrecorded heat gains.
Due to the increased impact of the luminous flux coming through the windows, in the warm season climatic technology spends half the power to compensate for solar heat.
The adjustment of cooling capacity is based on each square meter of additional glazing:
 + 200300 watts  for the sunny side;
 + 100200 W  moderate room insolation;
 + 50100 W  prevalence of shading.
Light blinds or curtains will help reduce solar heat gain.
Additional criteria for selecting air conditioning
In addition to the power characteristics of the system and the energy efficiency class, you should determine the following parameters before purchasing:
 type of air conditioner;
 the principle of operation of the unit;
 functionality;
 by the manufacturer.
Next, we consider in more detail each of these criteria.
Criterion # 1  air conditioner view
For home use are used monoblocks and split systems. The first category includes window models and compact portable devices. Window air conditioners have lost their former popularity.
They are superseded by more modern modifications, devoid of the shortcomings of their predecessors: noise in the work, reduced illumination due to clutter in the window, limited choice of location
The undeniable advantages of window "coolers": low cost and maintainability. This unit is more suitable for seasonal dacha use than for an apartment.
Mobile monoblocks are equipped with a flexible air duct that transfers heat to the street. A portable air conditioner is the optimal solution for a rented room. We have led the ranking of the best mobile models in this article.
The advantages of a mobile monoblock: the possibility of transportation, ease of installation. Minuses: large dimensions, high noise level, “binding” to the output channel
Split systems confidently occupy a leading position among household air conditioning systems.
According to the form of execution there are two categories of splits:
 Twoblock design. A pair of modules connected to a freon closed line. The complex is easy to operate and virtually silent. There are various options for decorating the indoor unit, the case does not occupy a useful area in the room.
 Multisystem. External module provides two to five internal blocks.
The use of multicomplex allows you to set different parameters of air conditioning in separate rooms.
The lack of a climate system is the dependence of indoor units on a single street one. If it breaks down, all rooms will remain without cooling.
Criterion # 2  principle of operation
Distinguish between conventional and inverter models.
The order of the traditional splitsystem:
 When the temperature rises, the air conditioner turns on.
 After cooling to the designated aisle, the unit shuts down.
 Duty cycle on / off repeats continuously.
But inverter air conditioner functions more smoothly. After starting the room is cooled, but the device continues to work with reduced power, maintaining the desired temperature.
Inverter version of the split is more economical than a normal air conditioner by 3040%. The value of energy efficiency EER of some models reaches values up to 45,15
Due to the lack of "sharp" cyclical operation of the inverter air conditioners are low noise and durable.
You don't know either which is better to choose  inverter or conventional air conditioning? In this case, we recommend that you familiarize yourself with their main differences, as well as the pros and cons of each option.
Criterion # 3  features and brand
Manufacturers, in an effort to win the location of customers, equip split systems with additional options.
Well, if the air conditioner has the following functions:
 fan distribution of air flow;
 automatic restoration of instrument settings;
 remote control;
 builtin timer
One of the most popular functions of air conditioning among users is fresh air intake. Many manufacturers offer such models.
Conditioners of popular brands are represented by a wide range of models of different price categories  from budget economy class to splitsystems of the premium segment.
A significant role when choosing a manufacturer of equipment  the better the brand reputation, the higher the quality and reliability of the equipment.
The ranking of leading manufacturers is dominated by foreign companies: Daikin, LG, Sharp, Hitachi, Panasonic and General Climat. The best models of air conditioners we considered in the next article.
Conclusions and useful video on the topic
Practical recommendations of a specialist will help determine the power characteristics of an air conditioner:
Understanding the principles of calculating the performance of air conditioning systems, it will turn out to independently determine the range of permissible power.
It is better to entrust the final calculation of suitable parameters to professionals  an experienced specialist will take into account all the operational nuances and select the optimal model of air conditioner.
You need air conditioning, but you do not want to lose money with power and choose insufficiently productive equipment in an apartment / house? Maybe you still have questions on calculations or want to clarify certain nuances? Ask for advice in the comments  our experts and competent visitors to the site will try to clarify all the points.