As with the laws of thermodynamics, there are three laws of home economics. The dedicated physicist should bare these in mind when setting up home.
1. Conservation of energy
No matter how often lights and appliances are switched off, elsewhere in the home, a spouse or child is turning on something else. This keeps the house energy levels constant. Adding insulation, energy saving bulbs and triple-A rated appliances will merely increase the number of lights and appliances that are switched on. This is a fundamental law and cannot be altered. Should the conscientious home owner pare down the electrical items to the bare minimum, energy prices will increase.
2. Entropy will always increase
We've all seen it. Seconds after you've tidied a room, you turn around, and your five year old son has emptied the toy box in the middle of the room. Some might argue that it is worth just saying "sod it" and leaving the mess. This would be a mistake. As with entropy, levels of tidiness always move from an ordered to a disordered state. The state of tidiness is a high energy state, ready to topple into the low energy state of untidiness with the slightest push. Children provide the ideal push. The only way to stave off the state of disorder is to provide no mechanism for untidiness to form, by owning nothing.
3. It is impossible to get down to zero
As with temperature, it is impossible to reduce household bills to zero. There are ways of decreasing the bills, such as only eating home-grown lettuce. However, due to the first law of home economics, it is impossible to reduce the energy bills down to zero. Various methods can be employed to reduce bills towards zero, and as with temperature, there will be initial large gains, but in order to make further savings, increasingly large efforts must be made to reduce the bills further. Furthermore, the closer to zero the bills get, the greater the effect of slight perturbations.
Unlike the laws of thermodynamics, the laws of home economics can be simply avoided by living at home with your parents, and not going out with girls. Something most dedicated physicists should find trivial.