Solar surplus prices drop sharply

The cost of buying back surplus electricity from private solar installations has fallen from nearly 13 cents per euro to just 1.1 cents per euro since June 1, 2026, according to a recent report. This steep decline has prompted homeowners with solar panels to look for ways to make their investments more profitable.

Batteries and solar routers as alternatives

To increase the profitability of solar installations, homeowners are turning to batteries to store surplus electricity, which can then be used later. Another option for smaller systems is the use of solar routers, which direct electricity from solar panels to high-energy-consuming appliances like water heaters or electric vehicle chargers, improving efficiency without the need for a battery.

Battery profitability varies by system size

Larger solar installations may not benefit from batteries, especially if they were set up when electricity purchase rates were higher and are now nearing the end of their contracts. The right battery size depends on the installation's power output, daily energy production, and nighttime consumption. A small installation may only need a 3 kWh battery, while a larger setup might require up to 10 kWh.

Battery installation costs vary

The cost of installing a battery depends on its size. A 5 kWh battery can range from 2,500 to 4,500 euros, while a 10 kWh battery can cost between 6,000 and 8,500 euros. Plug-and-play systems are generally cheaper but often lack installation services, and older systems may require additional upgrades like a new inverter, increasing overall costs.

LFP and sodium-ion batteries gain popularity

Lithium-iron-phosphate (LFP) batteries are becoming the standard for residential use because of their safety and long life, with most models lasting 4,000 to 6,000 charge cycles. Sodium-ion batteries are also emerging as a more environmentally friendly option with similar performance. Lead batteries, while still available, are not recommended due to their shorter lifespan when frequently used.

Key factors in battery selection

When choosing a battery, important factors include warranty length, depth of discharge, and power input/output capabilities. Most serious LFP battery manufacturers offer a warranty of at least ten years, with about 70% of the original capacity remaining at the end of that period. However, the actual usable capacity may be less due to the need to keep a minimum charge level.

Plug-and-play batteries have limitations

Plug-and-play batteries, which are easy to install, are popular but have technical limitations, such as a maximum power output of 800 W when connected to a standard domestic outlet. These limits are not always clearly communicated by manufacturers, and bypassing them can be unsafe. Legal guidelines for their use in solar systems are still unclear, with some experts advising caution until regulations are more defined.

Financial support and virtual storage options

There is currently no financial assistance for battery installation, though solar panels qualify for a reduced VAT rate of 5.5% under certain conditions. Some energy suppliers offer virtual battery solutions, allowing users to store surplus energy digitally. However, these options require switching energy providers and may involve activation fees.