Spending to make...

While it's a fairly common and reasonably accurate maxim that you have to spend money to make money, I find myself wondering if the same is true of energy. To reword and disentangle the metaphor: Can you save energy by using energy?

Here's a my train of thought: You have curtains in your house. It's possible to fit a motorised unit and automate the opening and closing of the same. This would same ostentatious, lazy and wasteful. To have a computer, sitting, always on, in your house, which decides when this should happen would seem to increase these negative factors.

But...

During winter, you try to close the curtains to keep heat in. Doing this early means you miss out on daylight and, furthermore, you have to turn on artificial lights. Doing this too late means that you loose heat through the windows. There's is probably a converse example in hotter climates than this, in which your house gets too hot in the middle of the day if you don't close the binds, meaning you have to turn on the air conditioning.

So then, at what point does the energy used to run the computer become a good investment? What if it has sensors inside and outside in order to measure the temperature gradient, and so it can choose the best time to close the curtains? What if it also manages your heating? What if it intelligently turns out the lights in rooms you're not in? Reminds you that you turned the oven on but haven't actually put anything in it... Makes damn sure that you get out of bed in the morning... and so on...