Whether constructing a new building or starting remodeling your old home, electrical load calculation is essential for your project planning. Calculating the electrical load will determine the total amperage needed to run your electric appliances. According to the report of 2023, residential and commercial buildings are major energy consumers, accounting for 26.7% of the total US enduse energy consumption.
So, by getting accurate electric load calculations, you can reduce the electricity bill of your building. This blog guide will help you calculate the electric consumption of your building. Let’s get started and get to know how to calculate total electrical load of a building.
How to Determine the Power Requirement for a Building?
One of the hardest things about the electric load calculation of buildings is determining the power requirements. In power requirement computation, three basic concepts are current, voltage, and electric power. Read more to get to know how you can determine power requirements.

Make a List of Electrical Appliances and Devices
Note down all the devices and appliances used in your building premises. This list includes computers, electronic security systems, lights, air conditioners, water heaters, kitchen stoves, refrigerators, and all other electric appliances.

Determine the Power Requirement of Each Device
Now, you have the list of all the appliances and devices used within your building premises. So, it’s time to determine the power consumption of each appliance. The power is calculated in watts or kilowatts. The power consumption is usually mentioned on the label or booklet of the appliance or you can calculate it manually. Here we have mentioned the power consumption of some common electric devices.
Appliances  Power in Watts 
Kettle Electric  1200 
Microwave  1000 
Compact Fluorescent  2228 
LED Bulb  1013 
LCD TV  150 
Ceiling Fan  120 
Computer  210 
Air Conditioner  3250 
Refrigerator  800 

Calculate the Total Power Requirement
Add the total power consumption of all the devices. You will get the total power consumption required to stimulate your building to function smoothly. However, the actual power consumption depends on many factors such as the number of hours these devices are used.
Understand this by a simple example. Let’s say your building appliances require 2346 watts to operate properly, but the electricity usage may vary.
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How to Calculate the Electrical Load of a Building?
Did you receive a high energy bill? Then it’s a good time to calculate the electric load of your building so that you can reduce your electricity bill. If you know the operating time and load in Kwh, you can easily control the electrical load of your building. So, let’s know more about how you can calculate this.

Calculate the Operating Time of Each Device
First, determine the daily operating time of each device. Each device has a different operating time as some run 24/7 and some are used only for a specific time.
For instance, in a building, an electronic security system works roundtheclock while other appliances like computers, electric stoves, or air conditioners are used when needed. So, determine the operating time of all your appliances that are available within your premises. Below we have provided a list of operating hours of various appliances.
Appliance Name  Operating Hours 
Computer  7 
Light Bulb  16 
Refrigerator  9 
Microwave Oven  1 
Air Conditioner  8 

Calculate Load in Kwh
To calculate the load in Kwh you have to calculate the electric load of each appliance in Kwh. To get power in kilowatts (Kwh) of an appliance, multiply the power rating (watts) by its operational time, and divide it by 1000.
Electrical Load in Kwh = Power rating in watts * operating hour
1000
Suppose you want to calculate the electrical load of your air conditioner in Kwh. so, put the abovegiven formula in this formula and get the electrical load of a conditioner in Kwh.
The electrical load of the air conditioner in Kwh = 3250 watts * 8 hours = 26 Kwh
1000
Likewise, calculate the load of a computer.
The electrical load of the computer in Kwh = 210 watts * 7 hours = 1.47 Kwh
1000
You can calculate each of your devices’ electric loads by the calculations mentioned earlier.

Consider Peak Load
There is a certain time during the day when the electricity is in high demand. This time is known as peak load time or peak load hours. When you calculate the electric load of your building, always consider these peak load times.
These hours are crucial as some appliances multiply your load too often when used during these hours. For instance, your electric load will increase drastically when you turn on your air conditioner and refrigerator. So, always be careful while using heavy devices in peak load hours.
You May Also Read: Electrical Estimating Methods
Understanding Watts, Volts, and Amps
As we mentioned above, calculating the electrical load of your building means adding up the amperage of all the electrical devices and appliances. Always keep the safety factor in your calculation and ensure that the total electrical load of your building does not exceed 80% of your electric load capacity. However, to accurately calculate your electric load you must understand the Watts, volts, and amps. These three terms have the following relationship,
Watts = Amps * Volts
Amps = Watts / Volts
These formulas can be used to calculate the electric load and capacity of each electrical system’s circuits. For instance, if you have a 20ampere current with 240 volts, the capacity is 4800 watts.
How to Calculate the Electrical Capacity of a Building?
Calculating the electrical capacity of a building is crucial as it ensures that your electrical system can handle your expected load effectively. However, to calculate your electrical capacity you have to follow some steps.

Evaluate the Building’s Electrical Needs
When you start to determine the electrical capacity of your building then you have to first evaluate its electrical needs. Make a list of all the appliances and devices that are used within your building premises. Ensure that you add up all the electrical devices.

Calculate the Total Electrical Load
The next is you must calculate the total electrical load of each of your electrical appliances. For this, add the appliance counts in your devices list and multiply the counts with the total wattages. Let’s suppose you have the following number of electrical devices.
Appliance  Counts  Wattages  Electric Load(watts) 
Light Fixtures  20  13  13*20 = 260 
Refrigerator  1  800  1* 800 = 800 
HVAC System  1  5000  1* 5000 = 5000 
Oven  1  2000  1* 2000 = 2000 
Other Miscellaneous Devices  #  500  500 = 500 
Now, add up all the electrical load to find out the total load.
Total electrical load = 260 watts + 800 watts + 5000 watts + 2000 watts + 500 watts
= 8560 watts
This load may vary depending on your electrical device’s power and their count. We have just provided you a exemplary calculations.

Convert to Ampere
Now, it is time to convert your wattages into amperes by dividing your total electrical load by the voltages. Usually, for residential and commercial buildings 120 volts and 240 volts are available.
Ampere = watts / Volts
Ampere = 8560 watts / 240 volts
= 35.66 A
For this value, you should select a service of 100A.

Consider Load Distribution
After ensuring that your circuit panel has enough capacity to handle your electrical load, consider a circuit distributor that distributes the electrical load across various circuits.
By following the abovementioned steps, you can easily determine the electrical capacity of your building and ensure the effective functioning of the electrical system.
Read more: Commercial Electrical Wiring Cost Per Square Foot
Commercial Electrical Load Calculations
You can calculate the commercial electrical load by a simple formula P = VI. If you know the voltage and current across each appliance of your commercial building, then you can easily determine the electrical load of each device by using the power formula. By adding all the load power of individual appliances, you can find out the total electrical load of your commercial building.
 Let’s say you have three electrical loads with the following current and voltage measurements:
Electrical load 1: 3 amps with 120 volts
Electrical load 2: 4 amps with 240 volts
Electrical load 3: 6 amps with 120 volts
 By using the power formula, you can calculate the power consumption of each load. Such as
For electrical load 1: P = 3 amps * 120 volts = 360 watts
For electrical load 2: P = 4 amps * 240 volts = 960 watts
For electrical load 3: P = 6 amps * 120 volts = 720 watts
Now add all the electrical loads,
Total electrical Load = 360 watts + 960 watts + 720 watts
= 2040 watts
This is the total load of your commercial building.
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How Do You Decrease the Electrical Load in a Building?
Reducing the electrical load in a building can save a significant amount of energy and reduce your electricity bills. Here are some ways through which you can reduce your electrical load.

Replace Your Lighting
Traditional fluorescent or incandescent lights consume a great chunk of electricity. So, if your building has this outdated light system, then replace this with LED lighting. LED lights have a quicker and more drastic impact on your building’s energy consumption as they save up to 60% of the energy cost of your lighting energy consumption.
Moreover, LED lights have a long life that helps you to save maintenance costs. And most importantly, this lighting system generates less heat eventually lessening the load on your air conditioner.

Regular Maintenance of Your HVAC System
An HVAC system comprises heating, ventilation, and air conditioning equipment. This HVAC system is made up of a wide network of ducts that distribute hot and cold air throughout your building. If these pipe ducts are not properly insulated then you have to face significant energy waste that results in waste of thousands of dollars annually on heating or cooling expenses.
So, regular maintenance or insulation can help you to reduce your electric load which ultimately saves 20% of your energy cost. Use EnergyStar Certified HVAC equipment that saves approximately $140 from your annual electricity bills.

Purchase Energy Efficient Appliances
When you purchase any energy appliance, always consider two key points; your appliance’s purchase cost and its annual operating cost. These two factors would decide whether your appliance is energy efficient or not.
Although energyefficient devices may have high purchase prices, these can save your annual energy costs. So, we recommend you to see Energy Star Label when purchasing any energy appliance. Energy Star Label is federally guaranteed that your appliance consumes less energy than other standard models.

Improve Building Design
Your building design and layout lessen your electric load significantly. Install skylight windows that allow daylight to enter into your building structure and minimize the need to turn on the lights. These operable windows allow hot air to escape into warmer months and reduce the load for air conditioning systems.
Moreover, you should plant evergreen trees outside your building premises that block the cold wind in winter and provide a refreshing shade into summer.

Install Programmable Thermostat
The main benefit of a smart thermostat is to turn off your HVAC system when you are away or asleep. According to Energy Star, a programmable or smart thermostat can save 9% of your heating or cooling bill cost. These thermostats can reduce your heating or cooling energy without replacing your HVAC system.
Moreover, these programmable or smart thermostat indicates when the air filters of your HVAC system need to be replaced further increasing the efficiency of your HVAC system.
Factors Affecting Electrical Load Estimation
Estimating the accurate electrical load is crucial to get a better design of your building’s electrical system. Here are some factors that can affect your electric load estimation.

 Building Design: Your building design and layout affect your electric load estimation. For instance, larger buildings with more number of floors utilize your energy load capacity.
 Type of Your Building: Generally, the type of your building significantly influences your electric load capacity. If your building is utilized for residential usage then your electric load is comprised only of lighting system, HVAC system, or personal appliances. On the contrary, if your building is used for industrial purposes then you need a higher power system for heavy machinery.
 Usage Pattern: Usage pattern and number of occupants of your building greatly affect your electric load estimation. As every occupant had different schedules and load requirements.
 Appliance and Equipment: If your building has more appliances or appliances with higher power ratings, then it will eventually affect your electric load estimation.
 Lighting and HVAC System: The light requirements of your building and the type of lighting system that is installed at your building can impact your electric load estimation as different lights have different power requirements. Likewise, the condition and model of your HVAC system affect your electric load estimation.
 Load Diversity: Consider the diversity factor as all the devices and electric systems are not used within the same hours or at the same usage pattern.
By considering these factors, you can get accurate electrical load estimation and ensure a safe electrical system design.
Common Mistakes to Avoid When Calculating Electrical Load
Calculating electrical load is a crucial task that needs precision and attention to detail. So, while calculating electrical load you must be careful to achieve accurate electrical load estimation. In this section, we will discuss some mistakes that you should avoid to get precise electrical estimation.

Ignoring Peak Load Hours
Peak hours are critical to consider while calculating the electrical load of any building. But most people ignore these peak load hours when highpowerrated devices are simultaneously used. So, when you estimate your building’s electrical load, always consider these hours to get an accurate estimation.

Overlooking Continuous Loads
In your building, some devices must be used for continuous hours (4 to 5 straight hours) like computers or HVAC systems. These continuous loads can impact your electrical load calculation so you should consider these loads at 125% of their actual load,

Underestimate the Future Expansion
It is a common mistake that majority of the people underestimate the future expansion of their building and design the electrical system as per the current needs. This factor influences the overall electrical load calculation formula so you must include a margin for future growth.

Getting Inaccurate Appliance Ratings
To get accurate electrical load calculations, always ensure that you are getting accurate appliance ratings. Inaccurate and outdated power ratings of the appliances would lead you toward false electrical load estimation.

Not Considering Local Codes and Rules
Calculating electrical load is an intricate process and you need to consider safety measures while calculating electrical load. So, always consider local codes and regulations to ensure your building’s electrical system will comply with them.

Neglecting Power Factor
Make sure that you always take into account the power factor while calculating the electrical load of your building. If you are not considering the power factor, you must underestimate your electrical load.

Not Conducting an Energy Audit
Energy audits are greatly helpful in identifying the areas of inefficiencies and potential load restrictions. So, never ignore the importance of an energy audit during the calculation process of your electrical load.

Not Consulting Professionals
If you are not good at calculation or have less knowledge of electrical systems, then never conduct electrical load calculations by yourself. Always consult with some professionals or licensed electrician or electrical estimator to get accurate electrical laid calculations.
Specialized Equipment Loads
The specialized loads include the industrial facilities. These are the equipment and heavy machinery. They impose specialized loads on the structure. These technical equipment are processing machinery, cranes, manufacturing equipment, largescale production systems and conveyors. Any operational load and equipment’s weight are included in industrial load equipment.
HVAC Load Estimation
HVAC (Heating, Ventilation, Air conditioning) is large equipment. They include chillers, cooling towers, handling units, and boilers. When you estimate HVAC loads, the teams and weights of these equipment will add up.
There are some other components associated with them. They are fans, ductwork, and piping. When HVAC load is estimated for commercial buildings, related features would be involved. In this way, the weight of HVAC estimates.
Conclusion
Calculating the electrical load of your building is crucial to designing a safe and efficient electrical system for your building. Moreover, understanding your electrical load can help you reduce your energy consumption, prevent electrical hazards, and get a better power solution.
By considering peak hours and continuous loads, complying with building codes and regulations, getting accurate power ratings, and consulting with professionals, you can get precise and accurate electrical laid estimation.
FAQs
What is an electrical load estimate for a building?
The consumption of power by each device is required to add up. Consider every appliance connected to the electrical system. Calculation of lighting, electrical devices and electronics. The electrical load estimate voltage, duty cycle, power factor and amperage. Accuracy is critical to prevent overloading. Ensure efficient and safe operation.
Why is it important to calculate an accurate electrical load estimate?
There are various reasons to calculate load accurately.
 It’s essential for occupants that this estimation is accurate. Otherwise, power outages, fires or overloaded circuits may occur.
 The electrical system should be balanced to save from unnecessary high cost of energy.
 Maintenance and installation costs can be reduced if the system size is appropriate.
 Correctly calculating the building’s electrical load is critical to comply with the building codes.
What are the different methods for calculating an electrical load estimate?
There are different ways to calculate this estimation. A few of them are more accurate. These are the number of occupants in a building, the square footage method and the energy consumption data.
What are some common mistakes to avoid when calculating an electrical load estimate?
Avoid these common mistakes while loading calculations.
 Be careful that you never underestimate the load. Otherwise, it will overload the system.
 Save your building from under or overestimation of burden. Factoring is essential in the factor of power.
 Account for every electronics, appliance, and other electrical device. It will be your mistake if you don’t consider all of these.
 Consider the duty cycle of all devices. The amount of their usage daily should be appropriate.
 Ignoring the electrical codes may result in severe hazards to safety.
How Do I Calculate Lighting Loads For A Building?
Lighting load requires amperage from the electrical circuit. It can then multiply with th limits of voltage. The total load of power news is subtracted from all the other loads to determine the lighting load. The unit formula will be like this: Volts * Amps = Watts.