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Solar Thermal 101: Sizing Your Solar Water Heater Tank

This is the sixth in a series of posts written by Free Hot Water’s co-founder and senior mechanical engineer, Gal Moyal. We’ll be posting this series every Wednesday, so please make it a date. Some of the information may be very technical, but if you have any questions at all, please feel free to contact us. We sincerely want to help. If you would like to have a more hands-on experience, explore our certified Free Hot Water training courses.  –Solar Fred.

Sizing Your Solar Water Heater Tank

The simple rule of thumb is that on average, you should consider 1.5 gal of hot water storage for every square foot of solar panel installed.

For example every FHW-FC7275 collector has 25.25 sq ft of active area (the “aperture area”). Therefore, on average a system with two FHW-FC7275 should have a 75 gal storage tank capacity.

Please note that this type of calculation is a rule of thumb and is only intended to give you a good “ball park” number. In reality, storage capacity should be calculated based on:

  1. Heat production capacity of the solar array
  2. Insolation
  3. Water usage patterns
  4. Desired water temperature
  5. System type

Free Hot Water Internal Coil Storage Tank

If you’re not sure of the storage capacity you need for solar hot water home or business, please email us at info@freehotwter..com and one of our experts will walk you through the process.

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