According to the pilot, after a normal start and runup, he departed the airport and climbed to the cruise altitude. After reaching that altitude, he noted a flashing message indicator on the GPS that stated there was an electrical system issue. The pilot informed air traffic control that he would return to the departure airport to repair the issue, and about 7 miles from the airport, the GPS and primary flight display began to flash. The pilot pulled the circuit breakers to the flashing displays and set up for a straight in approach to the runway. He realized the airplane needed to lose altitude and attempted to extend the flaps, however, the flaps did not extend. He reset the circuit breakers, but the flaps still did not extend. He continued the approach, mistakenly forgot to extend the landing gear, and landed on the runway with the landing gear retracted. During the accident sequence, the fuselage was substantially damaged. After the accident, the pilot realized that he was interrupted during his starting checklist and concluded that he did not turn on the alternators (alternator and standby alternator) during the start procedures. Therefore, the airplane avionics were running on battery power the entire flight, which resulted in a loss of electrical power. He reported no other mechanical malfunctions of the airplane that would have precluded normal operation prior to the accident.