I saved the receipts for a week to show my parents what they were spending vs the bills they had to pay. They still spend irresponsibly. What next. Their Jehovah witness devotion alienated most of their friends. They don't want me to help them with their finances anymore, they think I'm telling them what to do. Things are getting cut off as a result. Most recently I had to take another relative to the hospital (40 miles away) and my dad said don't do it. This relative takes them to the doctor when I am working and had taken me too. I went anyway, and my dad told my mom NOT to give me the keys anymore unless he approves. I'm a 50 yeast old woman. I am driving his truck because mine has been in the shop all summer. Overspending so I can't get it out. Whatever my dad says, mom complies, she is afraid I think. It's been 2 years of this cheap and I'm done. I came from 500 miles away to help them now I feel like I'm being slapped in the face.
If your dad isn't ready for you to take over his finances, there's not much you can do. People are allowed to be irresponsible with their own funds. It's possible, if you back completely off right now, that he'll see that he likes it better when you're taking are of things for them. But, in the meantime, it's their money. If they over-spend, it's on them. Unless you want to pursue a competency hearing, you're left with cajoling them and manipulating them into wanting your help.
It's not easy watching a parent more or less self-destruct. But, even if you had his power of attorney? He's still free to do as he pleases with his own funds.
Maybe the utilities have to get shut off before they realize they need to start budgeting. What are they overspending on? Trips to the casino? Stuff from HSN? Is this new behavior, or have they always thrown their money around like drunken sailors? It could be a sign of depression.
Maybe you should move out and leave them to sink or swim. It doesn't sound like the situation you're in is a healthy one for you.