Water pumps for Koi ponds
You want a pump that delivers the maximum volume but at the lowest possible running cost
These two are NOT necessarily the same.
When it comes to good Koi pond design a non pressurised filtration system will Always be cheaper to run - because your pump does not have to pump against the resistance that any pressurised system faces. Pumping against this resistance uses energy (in this case electricity) for which you pay.
Same thing applies to very high water features. Getting the water up there uses a lot of energy and your pump will cost you more to run as you will need a pump that can deliver enough energy to the job at hand.
Bear in mind that a pump uses a fixed amount of energy. Whether it runs at full tilt, or whether you throttle it back with a valve the pump will consume the same number of watts.
Hence a 100 W pump will use 100 watts whether it pumps 1000 litres of water up a height of 1 meters or whether it pumps it up 6 meters. All that differs is the flowrate at the different heights - at 6m you will get dramatically less water than at 1 meter, if indeed you get any water at all!
So consider your pumps carefully. We like to use low power consumption pumps that deliver large volumes of water but are not as good as pushing water high up or through pressurised systems. There is always a trade off between the cost of running a pump and between high flow rates through pressurised or even non pressurised systems.