Hi Don.
Generally, you only run 24/7 when you have a problem you're clearing like an algae bloom or you're converting from bacquacil to chlorine. Without knowing your pool or pump size it's difficult to know HOW long your pump should run but the rule is it must "turn over" your water once a day. In other words if your pool is 10,000 gallons, your pump should run long enough to filter 10,000 gallons a day.
But you can experiment if you have NO idea how big your pool is nor how much water your pump/filter move (in gallons per minute). Try running your filter for 12 hours, from 7am to 7pm and see if, with proper testing and treatment, the pool stays clean. That, alone, should lower your electric bill. If you are in touch with the former owners you could ask them: How long did you run the pump per day?
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