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Bosch instant Water Heater

Creating Hot Water, our biggest electricity usage

When it comes to budgeting your electricity usage it was important for us when designing our solar panel system just how much electricity we are using, and what was the biggest electricity usage amount and how in the future can we change this.

After several months of monitoring, we determined that the creation of hot water was our biggest user of electricity, our system was designed around a solar collector and a 180litre tank, heated by a 1500watt element when the temperature dropped below 50degrees.

Our Solar Collector setup

Obviously we were happy with our solar collector, during the day it would create hot water, and in the day and evening it would provide us with hot water, unfortunately that is where the good story ends, as during the evening cold water would enter the tank in order to replace hot water taken, and this would mean cold water all night and in the morning.

This temperature, was normally around 30 degress after a night meant the heating element would come on and due to the size of the solar collectors water tank, it would normally take up to 5 hours to heat the 180litres of water to 50degrees, this is where our energy was being used.

Our new distributed hot water heating system

An alternative to heating large volumes of water, that might be used, is to heat hot water as it is needed, these types of heaters are normally known as instant water heaters, flash water heaters or tankless water heaters and they come in gas or electric formats.

We decided that due to our use of water (we try to keep showers short, and are very water conscious) and as we are in the middle of installing a high power solar power system with storage batteries, that the electric tankless water heater system would be the way to go.

Studies have shown up to 40% savings in electricity due to the instant hot water function of these heaters, meaning we would use less electricity in order to still have access to instant hot water.

It is now the plan to start installing our distributed hot water system (also known as a decentralised hot water system), using a main 3o litre flash heater mounted near the solar collector tank that takes its cold feed from the hot water out of the solar collector, thus, it will only turn on if the temperature exiting the solar collector tank is lower than the temperature we set on the instant water heaters thermostat.

We will also be installing 2 litre smaller instant water heaters near the showers, and one in the kitchen, that will fill the gap of cold water that may be in the pipe, meaning less water loss down the drain.

We will report on its success, or issues in a future energy saving post.



Running the Farm estate of Mandorlaie is my full time job, ensuring that the grapevines, olive trees and vegetable garden is all healthy and producing excellent organic products for our clients. We produce Organic extra virgin Olive Oil and Organic wines which you can buy online.