Just buy yourself a power meter so you can measure the watts your pinballs are using during gameplay and idle.
When running idle I think it’s around 100W when fully in led.
A bulb takes like 6W were a led will be like 0.6W? So if on average 50 bulbs are burning you save 50x6 minus 50x0.6 makes 270W savings. Very rough calculation but gives you an idea.