Sizing MEP Equipment

MEP Equipment Power Rating Calculations

All right, now we come to an important part in the electrical design process for any type of buildings, this part states the used methods and approaches for sizing power ratings of all MEP Equipment used thought the building.

In this course, we will not use thumb of rules as many designers do for sizing the power rating of MEP Equipment but we will provide the professional way for doing such calculations which give more confidence for the designer about his calculations.

However, as a fast guide, we will refer at the end of the calculation methods for MEP Equipment to the famous Thumb of rules used and the conditions to use it.

MEP Equipment Power Rating Calculations

In below, you will find the list of MEP Equipment that we will explain their power rating calculations, this list will be updated regularly so, it is preferable if you register in our website to get the updates in your email once they had been issued.

Power Sources Equipment

Power Sources Equipment


Transformer Sizing Calculations


Generator Sizing Calculations

  1. Generator Power Ratings,
  2. Application type,
  3. Location Considerations,
  4. Fuel Selection Considerations,
  5. Site Considerations,
  6. Environmental Considerations,
  7. System Voltage and Phase,
  8. Acceptable percent of voltage & frequency dip,
  9. Acceptable duration of the voltage & frequency dip,
  10. Percent and type of loads to be connected,(Part One) (Part Two)
  11. Load step sequencing,
  12. Future needs.

Applicable Procedures For Generators Sizing Calculations for Existing & New Installations

Step#1: Determine the Required Generator(S) Set Rating,

Step#2: Assign the System Voltage and Phase,

Step#3: Segregate the Loads,

Step#4: Match the System to the Load Profile, Calculate the Required Number of Generator Sets and Paralleling Requirement,

Step#5-Existing Installations: Calculate the peak load of the installation,

Step#5-New Constructions: Calculate Connected Loads to Generator,

Step#6-Existing Installations: Check for transients or harmonics by using power analyzers and de-rate the peak load value.

Step#6-New Constructions: Calculate Effective Load to Generator,

Step#7: Adjust the Generator Rating According To Transient Voltage Dip,

Step#8: Adjust the Generator Rating According To Site Conditions,

Step#9: Adjust the Generator Rating According To Fuel Type,

Step#10: Adjust the Generator Rating According To Future Needs,

Step#11: Adjust the Generator Rating According To Power Factor

Step#12: Calculate the Adjusted Generator Rating,

Step#13: Select Generator Rating from Standard Sizes/Manufacturers Catalogs,

Step#14: Assign Required Number Of Steps/Starting Sequence.

Rules Of Thumb For Generators Sizing Calculations


UPS Sizing Calculations


Central Battery System Sizing Calculations


PV Photovoltaic System Sizing Calculations

Power Quality Equipment

Power Quality Equipment


Load Bank Sizing Calculations


Automatic Voltage Regulator AVR Sizing Calculations


Capacitor Bank For PF Correction Sizing Calculations

Glossary of Power Factor Correction Capacitors

MEP Loads Equipment

MEP Loads Equipment


HVAC Equipment Power Rating Calculations


Elevator Power Rating Calculations


Pumps Power Rating Calculations


Electrical Water Heaters Power Rating Calculations

1- Hot Water System Components,

2- Different types of Water Heaters used in domestic and commercial buildings,

3- How to choose the best type of water heater for any application?

Step#1: Determination of The Building/Occupancy Type
Step#2:  Calculation of The Minimum Number of Plumbing Facilities for a Given Type of Building/Occupancy

    Please, keep following this page for reading the above subjects which their links will be activated regularly.

    How to Register?

    To register as a member of Electrical-Knowhow website, do the following:

    1. Click on “Follow" in bottom of the home page, above the images of our members.

    2. Follow the instructions as in below image.


    3. After finishing your registration send email to, asking for your password and I will send it with email reply.


    1. need information on transformer sizing calculations

    2. can you please finish this section? i need the rest of the info

      thank you


    Leave a comment to help all for better understanding