Just a simple thing and not very significant. When the pressure increases the power consumption (current) to the pump decreases. Try putting a clamp-on ammeter on the pump line and see what happens. Look at the current (amps) full flow then blocked. Turns out that when the flow is totally blocked the power consumption is at a minimum. No water flow = no work done = low power consumprion. Specific to a centrifugal pump. On to the issue....I bored my return nozzles out to cut the pressure but I also know I don't have to run the system as long and therefore save some energy. Me thinks we're talking details that won't make much difference in the monthly $$ electric bill. As much as I'm being a monkey and tracking all this stuff, I haven't done it for this issue. So.....just my thinking and fodder for discussion.
Al