Here are more energy saving tips. This time for heating/cooling systems...
1) Use whole house fans, which pull cool night air into house through open windows. This save a lot on your AC bill. Attic vent fans, and cooling of the attic is essentially a waste of time. The attic does have to be properly vented with soffit, gable and/or ridge vents, but these are all passive i.e. no cost to run. Adding a fan to 'cool' the attic will not generate any savings--- PG&E has proven this. The only way this can work is by directly insulating the roof, which requires special, expensive insulation-not the pink fiberglass. Payback on this would be decade or more, if any.
2) Attic insulation: R30 or better! This translates to >12 inches of pink fiberglass or blown in.
3) HVAC plumbing/ductwork: Duct tape-that grey, fabric, sticky stuff is worthless, and is no longer code. What to use: Aluminum tape-it is like thick aluminum foil, with seriously sticky glue on back. If your house is > 7-10 years, then you could remove ALL the duct tape, and replace with the aluminum tape. This will stop leaks permanently!
4) HVAC vents into rooms: Use gaskets similar to the electrical outlet ones. And MOST important: Do NOT close any ducts! This significantly compromises the proper flow of heated/cooled air, makes you HVAC less efficient, and will make things worse if you have hot/cold spots or rooms. If you do have a room that is always too hot/cool, then have a HVAC contractor check the valves located in the ductwork. They can make adjustments there, where the system has been designed for adjustment.
5) In summer, close the blinds, especially on the sunward side! In the winter, open the blinds, especially on the sunward side! Radiant heating and cooling through windows can account for >10% or your costs! Those with double pane, reflectively coated windows will have a far lesser effect from this, but every little bit helps.
6) Water heater blankets: most model less than 5 years old don't need them; in fact, using one may void the warranty! Check you water heater labels carefully before adding.
7) Insulating hot water pipes: If you can get to those in attics, crawlspaces, and garages, that will help. Please note: on gas heaters, that short section of pipe (usually about 18-24 inches long) next to the vent pipe should NOT be insulated! This is a code violation is some locales, as the insulation required to make any difference will be too close to vent creating a potential fire hazard. In other words, don't bother with this section unless you have an electric water heater. This short section has such a small contribution to heat loss it almost isn’t worth doing unless you can do most of the piping.