The world's first solar-rechargeable tuner is the TC-1S from TASCAM: The TC-1S charges its battery from a bank of solar cells on the front panel in just 25 minutes, and a USB input is also available for quick-charging. From a full charge, the battery works for six hours of constant use and seven years of standby charge in a dark place. It's wrapped in a shock-proof silicone cover that's available in six colors and keeps the unit protected. 

The TC-1S has a built-in microphone as well as a 1/4" input for guitar and bass tuning. Its lightning-fast pitch detection is displayed on a wide bargraph display for instant feedback. Four display modes are available, including fine pitch display for 1-cent accuracy and strobe tuning animation. The tuner can be calibrated to an external source such as a piano or other hard-to-tune instrument. 

Included with the TC-1S is a nylon strap and clip. Snap it to your guitar or bass gig bag and it will stay charged all the time. 

• Chromatic tuner
• Solar-powered battery charging
• USB input for battery charging
• 1/4" instrument/microphone input
• Built-in microphone
• Custom LCD display with note, sharp/flat indicators, bargraph for pitch deviation
• Shock-resistant silicon case included
• Available in six colors: black, pink, orange, green, blue, white
• Includes strap and clip for attaching to instrument case
• Four display modes: Bar, Fine, Strobe Animation, Needle
• 12-note equal temperament scale
• Pitch displayed in 1 cent steps (in fine mode)
• 3.77" W x 0.71" H x 1.57" D (96mm W x 18mm H x 40mm D)
• 1.8oz (51g) weight

Battery specs:

• Continuous operation time: six hours
• Standby charge in darkness: seven years
• Charging time for 10 minutes operation, in sunlight: 25 minutes
• Charging time for 10 minutes operation, USB: 25 minutes
• Charging time for 10 minutes operation, indoor lighting (400 lux): 10 hours