How many hero shards does it take to raise star levels in Heroes vs Hordes?

A total of 1,225 hero shards are needed to get a hero to 4 stars starting from 0.

Star Level Breakdowns

0 star: 0 shards, max hero level 60.

1 star: 10 shards, max level 80.

2 stars: 65 shards, max hero level 100, skills can be leveled to rank 2.

3 stars: 300 shards, max hero level 125, skills can be leveled to rank 3.

4 stars: 850 shards, max hero level 150, skills can be leveled to rank 4.