What will a G2 driver on their parents insurance have to pay in insurance rates if they get in an accident?

I assume you are Canadian. I am as well, and I am a Broker. First of all, it's dependant upon if the accident was At Fault, so rates may not change. If you are at fault, no matter if you are dropped thereafter, there will still be a price hike. If it's not at fault, generally the rate should stay the same. Rates may double in the case of at fault, dependant on company. Being a G2 driver already means premiums will increase the parents' policy. If you are in an at fault accident, this will further raise the cost. If you were not at fault, the premiums should NOT increase.