Yes, it can be cost-effective to do laundry during the day using solar panels. Solar panels generate energy from sunlight, which means they produce the most electricity during daylight hours when the sun is shining. If you run your washing machine at that time, you can take advantage of the free, sustainable energy that your solar panels generate.

By using your washing machine during the day, you can reduce your electricity consumption during the hours when your solar panels produce the most energy. This limits the use of electricity from the grid and could potentially save you money on your energy bill. The exact amount of savings depends on the capacity of your solar panels, the amount of energy generated, and your own energy consumption.

Additionally, there are now smart devices and smart energy management systems available that can help optimize the energy consumption of your washing machine. These systems can automatically turn on your washing machine when your solar panels are producing enough energy and schedule the wash cycle based on the available solar energy. In this way, you can benefit even more from your solar power.

It's important to note that the exact savings can vary depending on your specific situation, such as the size and efficiency of your solar panels, the capacity of your home battery (if applicable), and your personal energy consumption pattern. It's advisable to monitor your energy usage and the energy production of your solar panels to gain better insight into the potential savings.