Advantages of the Optimum Sizing

Savings - Independence - Safety

The combination of a technology that avoids overheating problems with an optimised collector area provides you with maximum solar energy throughout the year.

On the basis of our calculation tools, Sunoptimo recommends the ideal number of solar thermal collectors that need to be installed to achieve an economic optimum. The calculation is based on hot water consumption, the area on the roof available and what is specifically sought in a solar thermal system (energy independence, maximizing the financial return on the investment, a fast return on the investment, ... ).

Thanks to drainback, the installation can exceed the traditional limit of 40-45% of the annual solar fraction recommended by most prescribers to avoid overheating of pressurised installations in summer. The more collectors you install, the more the solar system is able to cover a significant portion of your hot water energy needs (solar fraction).

The advantages of Optimum™ Sizing are therefore numerous:


  1. Lower installation price for a solar thermal system.

diminution du prix au m² système solaire thermique Sunoptimo

There are many fixed costs in a Sunoptimo solar thermal installation. This being the case, the larger the solar thermal system, the lower its cost per m². By calculating the economic optimum, it can be seen that it is preferable to install more collectors than is normally possible with a conventional "pressurised" system suffering from overheating problems in summer.





  1. Cheaper price per kWh hour

cout du kwh solaire

According to the change in the price of oil over a period of analysis, we can easily calculate the average cost of a kWh supplied by fossil energy (black, red and purple lines). Based on a price of €0.85/litre, the average price of a kWh provided by heating oil will be close to €0.20/kWh in the case of the first oil cost change scenario, €0.14/kWh in the second scenario and a little over €0.10 in the third scenario.

The price of a solar kWh is obtained by dividing the net cost of the installation by the number of kWh generated by the system during the period analyzed. This varies depending on the surface area of the collectors installed. Some people will choose the lowest price per solar kWh, that is €0.03 /kWh but this is a miscalculation. In fact, it needs to be viewed in relation to the solar fraction (the percentage that the solar system can cover in relation to the total energy need). The lowest price per solar kWh is obtained for a solar fraction of less than 50%. This means that the part not covered by solar has to be covered by much more expensive fossil energy. With a Sunoptimo solar system based on Optimum™ Sizing, the average cost of a kWh will therefore be much less because a much greater part of the energy needs will be covered by a solar kWh, much cheaper than fossil energy.


  1. Significant savings for water heating

evolution cout système solaire thermique Sunoptimo

The dotted curve corresponds to the total cost of water heating without a Sunoptimo solar thermal system, year after year. It is not linear given the change in price of the supplementary energy supply. The solid curve corresponds to the total cost of water heating with a Sunoptimo solar system. Each year, the Sunoptimo solar system allows substantial savings to be made. After just a few years, the total cost of water heating would have been identical, whether you had invested in a solar system or not. After that substantial savings will be generated as compared to the situation where a Sunoptimo solar system had not been installed. A Sunoptimo solar system does not replace the means used for heating the water (boiler) but the consumption of primary energy (oil, gas, electricity). Savings can quickly reach hundreds of thousands of euros.



  1. Independence from increases in the price of oil, gas and electricity.

Evolution du cours du pétrole les 15 dernières années

With a Sunoptimo solar system sized according to the Optimum™ Sizing principle, most of the energy needed for water heating will be covered by solar energy, therefore free after the investment. The cost of water heating will therefore no longer be subject to the vagaries of changes in oil prices. This much greater degree of autonomy in relation to fossil fuel prices will give you much greater financial security.
Once the investment has been made, no more unpleasant surprises for the next 20 years.



If you would like a survey to determine the benefits of installing a Sunoptimo solar thermal system and the savings you could achieve, please fill out the form.

Information on this page is provided for information purposes only. Under no circumstances does it constitute an invitation or offer to purchase. It is based on forecasts subject to a certain degree of uncertainty, in particular due to commercial, economic, meteorological or financial factors. Actual results may as a consequence be different from the forecasts.