12v Water Heater System using excess solar energy

Solar Green

Most boats only have hot water if they run the engine or are connected to shore power. Sitting for a couple of days in complete peace means cold showers and no hot water for the dishes. We have the solution!

SOLAR GREEN is our proprietary 12v electronic solar water heater control system. Much easier to install and more efficient than the alternatives – gas, diesel, or thermal panels – it uses surplus solar energy to heat the water in your boiler.

It does this by measuring

battery charge level
hot water temperature and optionally,
solar panel output

If the battery charge is at least 12.6v, the water temperature between 40° and 52°C , and there is at least 200w coming from the solar panels (option) the controller turns on the heating element.

How Does it Work?

Usually located in the same compartment as your boiler, the SOLAR GREEN controller is connected to your 12v batteries (lead/acid only). You can then either use

install a replacement 12v/300w heating element, or
connect to a dedicated 1500w inverter and your existing heating element or a replacement 230v/1200w heating element

The controller permanently monitors the battery charge level and if that is greater than 12.6v it then checks the water temperature if you have a replacement water heater and turns on if that is in the range between 40 and 52°C. An optional extra is an on/off switch that monitors solar output and makes sure the device does not switch on when solar output is less than 200w. SOLAR GREEN always switches off when the battery voltage level falls below 11.8v.

Product Options

Solar Energy Detector

If you draw hot water in the evening and the batteries are full, you could use electricity that you cannot replace. This option stops the unit from switching on if there is less than 12v coming from the solar panels. It has a manual over-ride.

External Status Monitor

Because the controller itself must be in the battery compartment, users often cannot see the status light The external status monitor repeats the status information and can be placed wherever visible and convenient.

Technical Requirements

SOLAR GREEN – the solar hot water controller – only works with 12v lead/acid batteries. Heating a 35l tank consumes around 600w (50A) and will take between 1 and 2 hours depending on the heating element and the cold water temperature.

Our recommendation therefore is that the minimum solar and battery configuration is 300w of solar and 200Ah of domestic batteries.