This paper presents a method for applying a web server based on ESP32 to a small photovoltaic (PV) power system to monitor and/or collect the PV and the battery current, voltage data. The designed system uses low-cost sensors, a microcontroller ESP32, Wi-Fi, and an SD-card reader. The ESP32 collects data from sensors. All of the data are saved in a text file on an SD-card, which is connected with ESP32 SPI pins. The text file is saved on the SD card for a week or longer, after which the system deletes all the data and starts saving new data. The web page file is saved on an SD card as well, so the ESP32 is programmed to access the web page by using the Wi-Fi via a laptop, cellphone, or tablet. Moreover, the web page has a link that allows users to download the data text file simply by clicking on the link. This can also be done remotely. The results of the experiments demonstrate that the web server works in real-time and can be effectively used for monitoring small solar energy systems.