Search for "tandem circuit breaker", it takes up two slots and provides 3 lines: a 240v line in center, plus 2 lines for 120v on the sides. Basically, you would replace the 2 slots for "SMOKE" and "Spare" with this new tandem breaker. This is exactly what I did with my panel. I had only one slot available, so I replaced the one next to it with a tandem breaker. Works like a charm. Now, I have a new 240v line with 50 amp load without upgrading my panel.