Installing solar panels at a home is an effective way to reduce electricity bills. However, for this investment to be truly profitable, it's important to use as much of the generated electricity as possible. If not used, any surplus is injected into the French grid, but since 2026, the compensation for this extra electricity has dropped significantly—now only about 0.01 euros per kWh, compared to 0.20 euros for electricity purchased from the grid. This makes it more financially beneficial to use the electricity locally, rather than sell it at a low price. A solar router offers a practical solution to this challenge. A solar router is a device installed in the home's electrical panel. Its main function is to detect when solar panels are producing more electricity than the household is using. When this happens, the router automatically activates high-energy-consuming appliances—like a water heater—to use the surplus electricity instead of letting it flow into the grid. This process is managed based on parameters such as the amount of solar surplus, how long it lasts, and the water heater’s maximum operating time. The router essentially acts as a smart coordinator, ensuring that excess solar power is used efficiently. For those interested in a more customized approach, it's possible to build a solar router oneself. While many ready-made options are available, DIY solutions can be tailored to specific needs. Communities like Home Assistant Communauté Francophone (HACF) offer extensive resources, including tutorials and user experiences. However, these projects require a good understanding of electrical systems and are typically aimed at more technically inclined individuals. While a solar router is a cost-effective option, it is not the only way to optimize solar electricity use. Another alternative is a domestic battery, which stores surplus energy for later use, such as during the evening. Unlike a solar router, which uses electricity immediately, batteries store it for future consumption. However, they are more expensive—often costing at least 600 euros for a 2 kWh capacity. Solar routers, on the other hand, are much more affordable, typically priced just over 100 euros. They are ideal for households that can absorb most of their solar surplus through appliances like water heaters. For such homes, the savings from using a solar router can amount to around 300 euros per year, making the investment worthwhile in one to three years. When choosing a solar router, it's important to consider several factors. First, ensure the model is compatible with your home's electrical system—whether it's single-phase or three-phase. Also, look for models that support peak and off-peak hours to maximize efficiency. Some routers offer remote control features, which can be useful for monitoring performance. Before installation, make sure you have the necessary skills or access to professional help, as installation requires working with your electrical panel. Additionally, most routers are designed for conventional water heaters, so if you have a thermodynamic model, you'll need a compatible router. Taking these factors into account will help ensure you choose the best solar router for your needs.