I realize it’s been a while since you posted this… I hope you have found a solution.
Let me prephase this by saying you’re almost certainly okay using a 30 amp breaker. The only issue I can foresee, is the device might burn out if there is a power surge on that breaker, since the breaker won’t flip until there is a higher load on it.
That said, I can suggest 2 other solutions.
1. If the panel has only big things like you say, there is almost certainly an open spot. You could always go out and buy a 15 amp breaker, and put it in yourself. Then you could connect the device directly to that breaker.
2. If there is an outlet near the panel, you can purchase an adapter on the emporia website, that allows you to plug the device into the wall. It’s less than $10.
Regards.
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