Does the 30% tax credit for solar panels apply for 2018. if my tax liability is 0 after itemized deductions why is it only showing a 15% tax credit?

[JulieR]

Yes, you can claim this non-refundable credit on your 2018 return.  Since this is a non-refundable credit your credit amount cannot exceed your tax liability. Any unused credit will carry forward to future years if your tax liability limits the amount this year. However, it is not yet clear whether you can carry unused credits to years after the solar credit expires. 

https://turbotax.intuit.com/tax-tips/going-green/federal-tax-credit-for-solar-energy/L7s9ZiB4D 

https://www.irs.gov/pub/irs-pdf/f5695.pdf