25w solar panel will produce about 100 - 120 watts of DC power per day, with this much power you can charge a cellphone, laptop, LED bulb, and small portable fan for a few hours. keep reading. Now I'll explain ho. a 25 watt solar panel will produce about 100 - 120 watt-hours of DC power output per day. Solar panels are designed and tested to produce their rated power under standard test conditions. ideal conditions include: 1. 1000. For a 25 watt solar panel, you'd need a 12v 30Ah lead-acid or 12v 20Ah lithium-ion battery. To calculate the size of a battery, multiply the highest number of peak sun hours your location receives (by month, In my case its 6.9 i. The charge controller is what regulates the power from the solar panel into the batteries. the voltage and amps fluctuate during the day due to different sunlight conditions, if you'll connect your solar panel directly to the bat. the inverter is used to convert the DC current into AC current to run our AC appliances, but we don't produce that much power from the 25w solar panels so that we can run large appliances like fridges, toasters, or TV. B.