Tesla has extended its free unlimited charging incentive through a new “referral program” that will be in place until the end of the year.

The automaker’s former offering was free unlimited lifetime charging for new vehicle owners, but that incentive program was supposed to end on Jan. 1 of this year. Tesla then extended the program for an additional two weeks before extending the cutoff date to last Friday.

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From now on, the only way for the owner of a new Tesla vehicle to receive free lifetime unlimited charging is to receive a referral code from an existing owner. Those owners will have five codes total to hand out before the end of the year, the automaker says.

If new Tesla owners are unable to acquire a referral code, they can still enjoy 400 kWh of free charging annually before they are forced to pay for the electricity. This should prove to be more than enough for most owners, seeing as the majority of Tesla owners charge their vehicle at home. Under typical driving scenarios, 400 kWh is roughly equivalent to 1,000 miles of driving range.