This calculator will not run on batteries, not solar, but… on water! You simply fill the water cell and the calculator is ready for use. Calculate anything you want… This calculator uses the innovative technology H2O, whereby the flow of water is generated by the calculator. You fill the water cell and the calculator is ready to use! Normally lasts 3 to 6 months in a full water cell, then just fill it back. The water cell itself last 2 to 3 years, then this can be replaced. The calculator is made of biodegradable plastic and is completely environmentally friendly and easy to recycle.