Using the energy calculator you may determine how much energy an Ejai solar collector will produce each day/month/year. The way you utilize this energy is up to you. You can heat water for showering and washing clothes, or central heat a building. In face one integrated system can complete both these functions.

You can also use these values to help you calculate how much energy you can save by using an Ejai solar collector.
In order to calculate energy output you must input the following

: Before  you calculate your energy output, you must know solar insolation level. This are available from the insolation page. Take note of your max and min levels throughout the year as well as the annual average value. When assessing potential energy savings, input annual insolation, and take

Note of the “per year” energy output value.
Energy must be input in the unit kWh/m²/day. 1 kWh/m²/day = 317.1 Btu/ ft²/ day
Collector Size: You must enter the collector size in absorber surface area.
The absorber surface area of the various tubes sizes are as follows:

  • 58/1800  = 0.08m² per tube. Therefore an Ejai AP 20 tube = 1.6m² absorber area
  • 58/1500  = 0.067m² per tube

Energy Cost: Enter must per kWh in your local currency
(may need to convert from m³ or Therms)
1 therm = 29.3kWh = 100,000Btu = 105.5MJ
Natural Gas is 39MJ/m³ = 10.83 kWh/m³
LPG Propane(liquid) = 25.3MJ/L = 7kWh/L
LPG Propane (gas) = 93.3 MJ/m³ = 25.9kWh/m³

  • When making comparisons with other products please take the point into consideration. Do not simply use the peak efficiency values for energy values for energy output, as this will provide inflated figures. IAM values also plan an important role in determining total energy output from a solar collector.
  • Monthly and annual values are calculated using 28 days and 336 days respectively to account for days of very low solar radiation.
  • Energy output values are approximations. Actual energy output and overall system efficiency will depend upon installation location, climate, insulation, system configuration and many other factors. On rainy or heavily overcast days energy output will be greatly reduced.
  • Energy is produced in the form of heat. In transporting and converting this energy, such as for air conditioning or central heating, some energy (heat) will be lost, as to insulation is 100% efficient.

Please Note:
Collector peak efficiency is only achieved when ambient temperature and water temperature are the same. During normal use, this is only likely to happen for a short period of time each day, and usually only when ambient temperatures are high (summer). Therefore during normal use, the solar collector can not always perform at such a high level of efficiency. This is true for all evacuated tube and flat plate collectors, not only Ejai collectors. In order to provide more realistic figures, the above calculations are based on “normal” operating conditions under which the difference between ambient temp and manifold water temp is around 30-40°C.


Split Series
Solar Collector
Balcony Series
Integrated Pressurization
Integrated Non-Pressurization
Pre-Heated System
Evacuated Tube
Solar Basics
How does solar help the environment?
What is Evacuated Tube?
What is Heat Pipe?
What is Insolation?
What is insolation in my area?
How much energy can solar collector Produce?
Ejai Installation Guide

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