The premise of the article - that the proportion of hours where hot water is needed is the same as the proportion of energy that is actually required - is false. Unless you have a terrible insulating system, a huge amount of energy isn't required to keep water hot. Most of your energy use should be in heating up cold water which is taken in to replace hot water used. You will not see a 66% reduction in energy costs; how much you will see depends on how good or bad your hot water insulation is, and the temperature differential between the hot water and the ambient temperature in its surroundings. Whatever that saving is, it needs to be compared with the opportunity costs of not having hot water whenever you want it, but rather having to stick to a schedule.
That's not to take away from the cool DIY scheduled servo job, which looks neat.