Replacing halogen with LED - will existing transformer work?
With the additional information provided these 12v lamps are designed to work with standard halogen 12v fixtures since your wattage of the new lamps is less than the wattage of the halogen yes they will work. It looks like 1/2 the wattage so there is the savings and in my experiance you will have more light or perceived light because light meters read light we cannot see where LED's produce light in a narrow band with so power is not wasted.