PV Solar Electric Hot Water

PV Solar Electric Hot Water


Solar electric (or Photo Voltaic –'PV') installations need to use as much power within the home as possible because 'feed-in' power is poorly rewarded.
Hot water cylinders store heat for later use at a far higher energy density than batteries and at a much lower capital expense.
Your hotwater cylinder can store 200-400% more energy than a modern 'house battery'
Use your hot water cylinder as a liquid battery instead
However, there are poor options to achieve this. Either just hope the cylinder element comes on at the right time (highly unlikely) or use a PV Diverter*. Problem is PV Diverters have poor hot water management abilities. Most don't even measure the cylinders' temperature at all. Those that do use primitive set point control.

The result is;
  • You can run out of hot water easily if the sun doesn't shine (sometimes even if it does)
  • You can over pre-heat the cylinder to avoid running out of hot water but loose storage capacity for the next day's sunshine
  • Most simply let you to run out of hot water and you have to press a button to start heating the water from cold, this can take 2 hours or more. Hardly a situation consistent with the year 2016


  • Smart Hot Water controller or Smart Cylinder (no external diverter);
    Your hot water needs heated anyway. Ensure this happens when you are most likely to benefit from surplus solar electric energy, around 10:00am to 2:00 pm in particular and store it for later use.
    You also gain from the efficient hot water management of a Smart Hot Water controller and all its benefits.
    The Smart Controller can be retrofitted to an existing cylinder or come as a complete Smart Cylinder for a new build or cylinder replacement.
    Don't use a timer for you hot water management. It is illegal under NZ law** and puts your family at risk from deadly Legionella infection. It also is unaware of how much hot water you have or require so you can run out of hot water or heat far too much from the grid supply.

  • Diverter and Smart Hot Water controller – The Best of Both Worlds
    1. Single element cylinder
      Diverters work well at ‘diverting’ surplus electricity but fail in cylinder hot water management.
      Take the best of the Smart Hot Water controller and the best of the Diverter and combine them in one package.
      Now you can efficiently divert your surplus solar electricity into your cylinder for later use while ensuring you don't run out of hot water and don't over pre-heat your cylinder.
      This solution requires 2 elements. One dedicated to the Smart Controller and the other to the Diverter. On a single element port cylinder (most common cylinder) it is usually possible to fit a dual blade element. Elements are wired to the Diverter and Smart Hot Water controller respectively.

    2. PV Solar Electric Hot Water

    3. Dual element cylinder
      Similar to above except there are dual element ports available. We recommend a Smart Cylinder for this.
      This solution is more efficient than solution A

    4. You selected the best solar power investment, now make sure your hot water supply and storage are not compromised. Enhance and complete your solar power investment with a Smart Hot Water controller or Smart Cylinder.

PV Solar Electric Hot Water

*A PV diverter is a device that measures power flows from the solar array and house consumption and proportionally allocates power to a hot water cylinder.

  • Low Voltage 24V PV to hot water element controller (DIY);
    Coming soon
    Using 24 volt panels, wire it yourself and save thousands. The Smart Hot Water Company is developing an entirely new type of solar hot water system.


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