Solar Water Heater Tank - Solar Storage Tanks

Solar Water Heater Tank

Solar Water Heater Tank - Solar Storage Tanks

SolarStor Solar Water Tanks are North Americas only complete solar water tanks and are UL and CSA certified. Unlike other tank manufacturers SolarStor tanks come complete with two large internal heat exchangers and a back up 4.5 Kw electric element ALL In One Tank!. This tank is suitable for all forms of solar heating systems including solar hot water heaters, solar home heating, solar pools and hot tubs! With this tank you can easily expand your solar heating system at any time without new equipment!

Solar water tanks are used in solar heating packages to act as buffer tanks. When the sun is shinning, the water will be heated in the solar storage tank for later use, most commonly in the evening. Most solar water heaters contain a heat exchanger to separate the potable water from the solar heating solution (Water/Glycol) and have a great insulation value that can retain the heat for day. The SolarStor tank has a rated heat loss of less than .8 degrees F/ Hour!

There are 3 kinds of solar water tank systems used in North America:

  • Solar Pre-Heat Tank
  • Solar Combo Electric Tank
  • Solar Dual Heat Exchanger Tank

SolarStor Water tanks are North America's Only 3-In-one solar water tanks.

3- In-One Solar Tank

Solar Pre Heat with existing heater

Solar Pre Heat with existing heater

Pre-Heat water for use with existing water heater

Solar Heater with electric back up

Solar Heater with electric back up

Replaces existing tank comes with 4.5 Kw back up

Solar Water with 2nd Heating zone
Solar Water with 2nd Heating zone

Top Heat Exchanger can be used for 2nd home heating loop

SolarStor tanks can offer 3 types of Heating configuration for now or Future

Pre-heat tank for hot water heating

Pre-heat tank for hot water heating

The 1st and most common solar heating tank configuration is a Solar pre-heat tank for hot water heating. This type of solar heating system is used in homes with an existing water heater (electric, oil, gas, tank-less). The pre-heat tank stores the solar heated hot water which is then drawn into the main tank when the hot water faucets are open. This type of system uses the large 14 ft2 internal heat exchanger to heat the potable water in the tank. The pre-heat tank heats the otherwise cold ground water before it enters the normal water tank. In this way ground or main line water of approx. 35 F can be preheated to say 120 + degrees before entering the primary heating tank. If the heating tank is set to 130 degrees, it only needs to raise the water 10 degrees instead of the 95 degrees it would have otherwise had to with out the solar pre heat-tank.

Pre-heat tank for hot water heating

Combo tank with solar and Electric

The second type of solar water heating tank configuration is used as combo tank with solar and Electric. The combo tank uses the built in 14 ft2 heat exchange on the bottom of the tank and also uses the middle 4.5 Kw heater element as back up. The solar hot water is circulated through the solar loop and through the internal heat exchanger heating the water in the tank. The element will then add to, and top up, the tanks temperature to the desired setting. This type of system is great for new homes or replacement tanks. It is important to note that very few solar water tanks found in North America meet UL or CSA certification as a combo tank, as such most European or Asian manufactured solar tanks can not be used with potable (drinking water).SolarStor tanks are 100% UL listed and can be used in any solar application in US or Canada.
Dual solar heating applications

Dual solar heating applications

The final type of solar storage tank configuration is suited for dual solar heating applications and uses both the top and bottom heat exchanger with/without the electric element supplement. In this tank configuration, the bottom heat exchanger heats the water from the bottom, The upper heat exchanger loop is found in the hottest part of the solar tank (hot water rises). This hot water surrounds the upper coil which then transfers this heat to a second heating zone such as radiant floor loop or to a furnace air to water heat exchanger. This type of solar storage tank configuration is designed for both heating applications and/or domestic hot water. In this configuration the customer can still use the electric heating element as it is include on all tanks. This allows customers to use SolarStor tanks as a complete Hydronic Heating System Boiler. However, unlike other boilers, this is supplemented by free solar energy!

Sizing a Solar Water Tank

When sizing a solar water tank, you need to consider two important variables. First, how much draw is used per person in the house? An average household will consume 20-30 gallons per person. This includes shower bath water, dishes, and laundry. So, a family of two will normally require a 40-gallon storage tank as a minimum. Secondly, each single vacuum tube will heat about 2 gallons of water. It is very important that you don't exceed this number, or you will find that in peak summer months your solar system may reach extreme temperatures. It is better to have a system that is under powered than overpowered. Our TZ58/1800-30R solar evacuated tubes have 30 tubes and are able to heat 60 gallons or more. So a 60 gallon or larger water tank would be a match for a 30 tube collector.  Since 60 gallons is an odd sized water tank, we would normally pair this with an 80-gallon water tank.

Solar Expansion Tanks

Solar Expansion Tanks

Another type of solar storage tank that is needed and often overlooked is an expansion tank found on the closed loop solar side of the solar heating system. All closed loop solar heating systems must have an expansion tank. Sizing of the expansion tank is very important. Northern Lights Solar Solutions has Italian manufactured Zilmet Solar Expansion tanks. These are the only tanks that are manufactured specifically for solar heating applications and can withstand higher temperatures than other hydronic style expansion tanks. Learn more on solar expansion tanks by clicking link.


G-GLASS porcelain fused-to-steel is impervious to chlorine and caustics - the ideal water vessel
1” NPT connections
2” Non-CFC zero ozone depleting foam insulation
Two magnesium anodes
Factory installed brass drain valve
Factory installed T&P valve
3-Year tank and heat exchanger warranty - non-residential application
Precision manufactured tank - high quality steel to assure strength and durability
6-Year tank and heat exchanger warranty - residential application

Technical Specs

heat exchanger specs
SolStor Solar Water Tanks

Solar Hot Water Tank with a External Heat Exchanger

Solar water heating system

The SolarStor Series of solar tanks are an excellent choice for most solar water heating applications. However, for those on a tight budget, there is a very affordable way to create a solar storage tank using either a new or used electric hot water tank and an external heat exchanger. Any tank can be used including a propane or natural gas tank. An average hot water tank can be purchased for $300-$500 and converted in minutes for under $10 in parts plus an external heat exchanger. To convert a hot water tank, we simply remove the bottom drain and add a “Tee” and extension nipple to this.  We do the same with the “T & P” valve at the top.

Now we connect the two “Tees” to a solar heat exchanger from the bottom and the top.  We will add a small circulation pump that will push the water from the bottom to the top of the tank.  On the other end of the heat exchanger (HX) we will attach the solar thermal loop that will bring the hot heating fluid through the HX.  In the exchanger the hot solar liquid will transfer its energy to the colder water coming from the bottom of the domestic hot water thank.  Our RESOL BX controller will handle both pumps such that it will turn them on when there is solar energy available to transfer.  At night both pumps will be turned off. 


When doing a retrofit tank system, it is important to note the directions of flow. The hot solar water and cold domestic hot water need to flow in opposite directions. This is called “counter-current” flow and results in the best heat transfer.