TLDR: **Ask the power company** what size your service is. There may also be evidence on the meter or meter pan. This is a classic "Rule of Six" panel ---- Where's the main breaker? Electrical service to houses used to be 60A. As it got bigger, there was a problem - large breakers like 100A or 200A were very expensive. A compromise was struck where the "main breaker" could be *up to six* smaller breakers. That's what you see in the upper part of this panel. They are not paralleled! Each of the breakers serves a different load. This panel, like many "Rule of Six" panels, has its own built-in subpanel - that's what you see in spaces 17-28. The subpanel area is fed by one of the six breakers in the "Rule of Six" area. This feeds all other loads in the house. (Space 15-16 are not spaces, the lids are renovable but there are no busbars behind them.) Your loads ----- What is in the upper area? Probably, based on labeling, - space 1,3 50A ?????? - space 5,7 50A air conditioner (a little large? Maybe a heat pump with aux heat?) - space 9,11 50A the subpanel below - space 2,4 40A range/oven - space 6,8 30A ?? likely an. electric dryer - space 10,12 30A water heater You notice this adds up to 250A -- there's no such service size. You also notice the subpanel breakers add up to *way, way* more than 50A, so you can see it's normal to *oversubscribe* breakers on a service. **Actually, breakers are there to protect wires and appliances**. Wire size (e.g. 12 AWG) decides breaker size (e.g. 20A). What size is my service? ----- As far as the subpanel area, your service is 50A, but hold that thought. As far as the capacity of the "Rule of Six" area, you'd need to consult with your power company or look for evidence at your meter or your meter base. Keep in mind you only have 5 breakers in the "Rule of Six" area and you are full. You can get CH breakers up to [100A][1] ($50) or [125A][2] ($110) in the normal shape (which would force you to abandon one large appliance)... or [150+ amps][3] in "Beast mode" packaging, where the breaker is 4 spaces wide (elimintating two large appliances). The problem with the "Rule of Six" design is there is bo main breaker to keep you honest, so nothing really keeps you from putting in six oversize breakers, maxing all of them, and setting your electric meter on fire. That's why Rule of Six was outlawed. You can't buy a panel like that today, and you shouldn't continue this one in service any longer than you have to. Get a better panel and make this a "Rule of One" panel ----- If it was my house, I would add an additional sub-panel quite near this one, and move all my loads to it. Then I would fit one of those big CH breakers in the "Rule of Six" area and have it only power that subpanel. Put blanking plates over every other space in the old panel, and you now have reduced it to a giant main breaker only. CH is a fine panel, outside of the serious defect of being "Rule of Six", and I would even consider CH for my new subpanel. Reuse all your breakers! it needn't be done in one sitting. Find a period when you can do without enough loads out of the Rule of Six area to make room for the new breaker (like A/C in winter). Once you wire up the new panel, at that point both panels are live, and you can move the other loads at your leisure. [1]: http://amzn.to/2y3jhJg [2]: http://amzn.to/2y3lQuP [3]: http://amzn.to/2z2qBTR