gas heater timer
IF the unit has an electronic ignition you can put that on a timer as well as a power vented type. Standing pilot? Really difficult, invovles cutting gas lines! You would have an electric gas valve open to the main burner, but not the pilot, and it would be controlled by the timer. This won't save you much, payback would be long. Insulation is the answer for some savings. Be sure the pipes (in AND out) are wrapped for about two feet. Wrap the entire tank with fiberglass wall insulation (get fireproof) and be sure to leave all air vents exposed. L brackets glued to the side will support tha fiberglass. The exhaust must have at least three inches of space around it. Peel away the paper backing for the part on top of the tank, it burns. This looks tacky and makes your plumber question your sanity, but it's cheap and may save about 15%.
Instead of using the t'stat to turn it up and down, use the gas valve to turn it to "pilot". I've left them that way for weeks at a time and haven't voided my homeowner's yet!