The U.S. Congress has (or will later this week) passed a law making the purchase of electric motorcycles and certain home charging equipment subject to a 10% tax credit of their cost during the years 2018 to 2020. This can be a decent amount of money. When I purchased my 2018 Zero in 2017, I received a check from the U.S. Treasury in the amount of $1,830.

So far, I have received a 10% tax credit (or rebate, if you prefer) for each of the five electric motorcycles that I have purchased during the past 10 years. (In addition to the $900 cash rebate from the state of California. Unfortunately, that rebate has recently been revised so that it only applies to one electric motorcycle purchase during a person's lifetime.)

Here is a link to the article announcing this change in the current tax law authorizing the credit:
https://electrek.co/2019/12/18/us-ex...retroactively/

At one time this rebate also applied to EV conversions, but I have no idea if that is still the case.