Our solar fountain pumps have been designed from the ground up to provide optimum performance for our fountains with or without the sun. Here's why! We have designed the pump to run off of lithium ion batteries which in turn are continuously recharged from the sun. On a full charge the pump will run for 10 hours without any sun and as soon as the sun hits the solar panel, the batteries will begin to recharge again. It takes approximately six hours of full sun to recharge the batteries. The batteries have been designed to give you years of maintenance free use, however, the batteries can be replaced if they ever won't hold a charge. The solar panel features a 10 foot cord so it can be positioned away from the fountain and in direct sunlight.