A twenty-five year rated polycrystalline solar panel is included. It is a high quality solar panel unlike those used in garden lights which are only good for 3 - 5 years. Only about an hour of direct sunlight is needed per day to charge the batteries. It will still charge if you put it in a lightly shaded area. Included with the solar panel is a 15 foot exterior rated cable so there is flexibility where you can place it. It is recommended to put in on the wall or roof of your coop.
The solar panel charges four Energizer AA rechargeable batteries which are included. These are the latest technology nickle-metal hydride batteries that are low self-discharge. Depending on the weight of the door, the batteries can last a month without charging because the circuit only uses a very small amount of current. When they need replacing (all rechargeable batteries need to be replaced at some point) be sure to use only Energizer nickle-metal batteries since the circuit was designed specifically for that brand. You can buy these at your grocery store, pharmacy store, or any of the major retailers and hardware stores.