You can calculate how many solar panels you need by dividing your yearly electricity usage by your area's production ratio and then dividing that number by the power output of your solar panels.
Typical cost range for adding or replacing a 2-pole 220 breaker generally falls between $85 and $680, with most residential installations landing around the $125–$250 mark for a standard 20–30A breaker. For higher amperages, AFCI/GFCI protection, or difficult access panels.