Electricity storage for your home - getting more out of the sun

Every owner of a photovoltaic system knows the phenomenon: the sun doesn't always shine when you need it. In everyday life, we need a lot of electricity, especially in the morning and evening hours: For lighting, heating, charging the electric car or bike or for the washing machine that is run after work. Homeowners are left with no choice but to buy expensive electricity. There is a better alternative: electricity storage for your home.

How an electricity storage system for your home works

In principle, an electricity storage unit is nothing more than a battery that is directly connected to the photovoltaic system. During the day, when the sun is shining, the electricity storage unit is charged with the solar energy that you do not directly consume. During bad weather and in the dark hours, the battery will supply your household appliances with electricity.

There are two storage systems: AC system and DC system.

AC stands for Alternating Current and DC for Direct Current. Photovoltaic modules always generate direct current, i.e. DC. AC storage systems are therefore not connected directly to the solar modules but are coupled to your installed photovoltaic system via a battery inverter. The battery inverter converts the direct current into alternating current for use in your home. An AC storage system is thus suitable for retrofitting existing PV systems.

• AC storage systems are based on their design ideally suited for retrofitting electricity storage.

DC storage systems combine the solar inverter and the battery inverter. The direct current generated by the PV system is not immediately converted into the alternating current but is stored by the electricity storage unit. If you need this electricity at home, the storage unit is discharged using the integrated solar inverter. This results in fewer conversion losses, which make the DC storage system more efficient.  

• DC storage systems are based on their design suitable for new PV system installations.

RCT Power offers both AC and DC systems, so you can build your home electricity storage system for an already existing PV system as well as for planned new PV system installations.      

What battery type is suitable for your home?

Some everyday appliances are often still powered by lead-acid batteries. Smartphones or even e-cars are now usually equipped with lithium-ion batteries, which have a high energy density and a long service life. For home electricity storage solutions, another battery technology is recommended: lithium iron phosphate batteries. Lithium iron phosphate batteries convince with high cycle stability, short charging times and strong discharging currents. They are very robust and have a lower risk of overheating than lithium-ion batteries because the energy density is not as high. At the equivalent nominal power, they are, therefore, slightly larger. However, this is irrelevant for a stationary power storage unit in your home. After 10,000 cycles, lithium iron phosphate batteries retain 80 per cent of their original capacity. After 15,000 cycles, it is still 60 per cent.

RCT Power makes us of the proven lithium iron phosphate technology and, in addition, optimally matches battery and inverter. Independent tests endorse the company's approach. RCT Power's 10 kWp system was ranked top in the 2021 edition of the annual energy storage inspection by the University of Applied Sciences (HTW) Berlin. It was the most energy-efficient system on the market. With a System Performance Index (SPI) of 95.1 per cent, the RCT Power Storage DC 10.0 with the RCT Power Battery 11.5 achieved the highest system efficiency of all systems tested to date.

Optimal storage unit size for your home

Electricity consumption in households varies and is very dependant on the individual setup. For a 4-person house, most providers calculate at least 3000 kilowatt hours (kWh). If you use electricity for hot water or heating, you can quickly reach 5,000 kWh and more. Add an electric car, and it can easily be 8,000 kWh per year. Many factors play a role in determining the required size of the electricity storage unit. 

• Consumption behaviour of the residents
• Special electricity consumption connections such as electricity-operated heating/heat pump
• Output of your PV system
• Self-consumption ratio
• Economic efficiency of the PV system and the electricity storage unit

When installing an electricity storage system, it is therefore highly advisable to consult an expert who will calculate the required storage capacity and design the system accordingly.   RCT Power offers electricity storage units with a nominal capacity of 3.8 to 11.5 kWh. The system is modular can be retrofitted and adapted. The system can thus grow with your requirements.

Profitability of electricity storage systems for your home

From a climate policy point of view, there is a worthwhile case to install an electricity storage system in your home. These systems are an important component of sustainable energy supply. The more self-produced electricity you consume, the better it is for the environment.

The profitability of electricity storage systems from an economic perspective is also steadily increasing. One factor is that the feed-in tariff to the grid continues to fall, on the other hand, the price of electricity continues rising. In September 2021, for example, the market price for a megawatt hour of base-load electricity was above 100 euros for the first time. With every kilowatt hour of electricity, you consume yourself, you save more than 20 cents compared to the electricity you buy from your supplier (data for Germany in October 2021). It means that the more self-produced electricity you use, the better the ratio of investment and savings for your PV system and your electricity storage system will become. With an PV storage system, you can increase the self-consumption ratio to up to 70 per cent.

Get specialist advice on electricity storage systems

Would you like to learn more about electricity storage systems for your home? Do you need a detailed capacity calculation? Contact our competent specialist partners. They will be happy to advise you personally. >> Find a specialist partner