FAQ

What is an off-grid solar power system?

An off-grid system is different from a grid-tied solar power system, in the way that it is not connected to the electrical power grid. Instead of sending the surplus electricity from the solar panels out into the grid, an energy storage system is used, such as a battery bank, which can supply the household with power when the sun isn’t shining.

For whom is it suitable with an off-grid system?

Off-grid systems are suitable for locations where no connection to the power grid is available. It can also give a satisfactory sense of freedom to be self-sufficient in electricity.

How are the calculations performed?

Your solar power system is designed by running electrical simulations in an engineering simulation software. The simulation looks at your battery bank, being charged up by solar panels and discharged by your electricity consumption during several days with varying weather. In order to make your system work when it is cloudy and the sunlight’s irradiance is low, a scenario is simulated where it is cloudy for several days (for example 10 days), followed by one day of average irradiance (the power in the sunlight). The goal is that your battery bank should be able to supply your electrical devices with power even as the weather is cloudy during a period of time. The battery bank’s state-of-charge should not fall below 50%, (which can be harmful for lead-acid batteries), although your electricity consumption continues as usual. On the following day with average solar irradiance your battery bank should become fully charged again. It is up to you to choose how many days of cloudy weather your solar power system should be able to deal with. You can also choose how many days of average weather that are necessary for charging up the battery bank again.

What do I get if I order a solar energy calculation?

You get an answer to the question of how many solar panels and batteries that are necessary for supplying you with your electricity consumption, depending on the sunlight’s irradiance at your location, as well as on how much electrical energy you consume. If you click on How it works in the menu you can see a an example calculation done for a solar power system in Madrid.

How can it be known whether the simulation results of Sunny off-grid are correct?

The simulation results of Sunny off-grid have been compared with simulations of possible solar power production around the world (see this graph), done by the World Bank. The results were almost identical, deviating only about 5 to 10 percent.

What does the 14 days return-policy mean?

Sunny off-grid implements a 14 days return policy, which means that you are entitled to a full refund within 14 days after your order, in case you are not satisfied with ourservices. You do not have to state a reason for why you are not satisfied.

What information do I need to fill out when ordering a solar energy calculation?

When you place an order you are asked to specify your electricity consumption and the location where you want to build your solar power system. You also fill out which months of the year you want your system to work without problems. This is necessary to know for the calculation, since both the sunlight’s irradiance and the temperature varies a lot for different months of the year. A larger solar power system is necessary if you want to use it during the darkest months of the year.

In what way are the calculations of Sunny off-grid different from other solar power calculation services which are available for free online?

Sunny off-grid gives you a personal evaluation of what you need, based on a worst-case scenario where the weather is cloudy during several days in a row. The simulation, performed by an electrical engineer, shows you how the battery bank’s state-of-charge varies over time during the days which are simulated. Many other services that dimension solar power systems only look at the annual average of incident solar energy. Such a calculation method can be relevant for grid-tied solar power systems, but they are not enough for dimensioning an off-grid system. A calculation based on average irradiation can give you a picture of how much electricity will be produced yearly, but it does not protect — the battery bank against becoming fully discharged (and thereby damaged) during periods of cloudy weather.

Many companies within solar energy also provide package solutions for the complete construction of your solar power system, where calculations, gear and the construction work have to be bought at the same time from one company. This can make it hard for the customer to estimate whether the cost for the solar power system is feasible. It can often be less expensive to buy the solar panels and batteries yourself for a better price, before an electrician is hired for the installation.

Are calculations for grid-tied solar power systems also offered?

Grid-tied solutions may be offered in the future, but it is not something Sunny off-grid performs at the moment.

Who is responsible for the safety in my solar power system?

You are responsible for that your solar power system is made safe. Sunny off-grid merely provides you with information about the appropriate number of solar panels and batteries for your system. It is recommended that you hire an electrician or another certified person for the installation.

Does Sunny off-grid sell solar panels and batteries?

No, Sunny off-grid only performs calculations for solar power systems.

Can I get further help with my solar power system, in addition to the dimensioning service?

Yes, electrical engineering consultant services can be offered to a price of 50 euros per hour, VAT included.