I am not too familiar with these systems but if it shuts it off- just like a timer would- and it is for a period of at least an hour, it would have no negative impact on the pump. Now, the photocell does not turn the pump off, it drops it to Power 2 so it just makes for a slower constant flow rather than off. This is safer for one reason. Small dotybacks, damsels etc. may go in the pump while it is off and get pureed. It is unlikely but it is more like impossible if the pump doesn't turn off. FWIW the photocell is less than $12, I don't know how much the X10 deal is.