Large savings can be achieved:
A high level of energy savings with a factor 7-9 can quickly reduce costs. However old 12V power supply units have problems with the LED technology. Instead of 10x 50W halogen lamps, the power supply must only deliver 10x 6 Watt LED. Often this works not because of undersupply.
Replacing old power supplies?
Old power supplies do not always provide a constant voltage-output. This can result in failing GU 5.3 LEDs or a much shorter life-span than specified. So it is advisable to install a suitable LED Power Supply (dimmable or not) Along with the replacement.