While the National Electric Code (NEC) has not specified a minimum, ideal and maximum height for electrical meter boxes, the utility company does. While utility companies may differ, most agree that the centre of the meter box should be between four feet and six feet above the ground.
The current price of a first class stamp is 49 cents. A domestic first class letter (1 oz.) is 49 cents. The price of each additional ounce is 21 cents. It will cost you 34 cents to send a domestic postcard.
Short answer, currently 47 cents (US). Long answer, Forever stamps will always be worth whatever the current 1st class standard 1 ounce letter rate is. That rate may increase to 49 cents on Jan. 22nd. In which case, any Forever stamp would be worth 49 cents.