Solar Panel

The Solar Panel is a Minion Fuel that can be used to speed up a Minion, and is unlocked at. It increases the speed of your minion by during the day when placed inside the Minion Fuel slot in the Minion GUI. Unlike most other fuels, it has an unlimited duration. It is not consumed and will be returned when clicked or a minion is picked up.

Day Saver
Using it in addition to a will cause it to run permanently.

However, the Day Saver does not work when you are offline thus the Solar Panel only provides an effective increase in minion speed when you are not around.

It might be better than the if you have a Day Saver and an alternate account that is constantly AFK on your island as it will then give a  boost to minion speed. The Day Saver can be considerably more expensive than a Enchanted Lava Bucket due to an extremely high Bazaar cost, in which case the Enchanted Lava Bucket is a more preferable option.