Super King Air 200
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Weather / Turbulence
Flight Crew Overcame Equipment Problem; General Declared Emergency
Aircraft; Weather
During cruise in level flight the No 1 right bus C/B popped. I did not notice any loss of aircraft function or instrumentation. I had all the anti-ice equipment on as I was in icing conditions. I turned off the right window heat and the aft medcrew lifeport power supply.  About 5 min later the left No 1 C/B popped and all cockpit light and EFIS went out. I turned off the forward lifeport power and the anti-ice; I was out of icing conditions at this time; and I turned environmental mod controller to off which turned off the vent blower. I then reset the LEFT No1 C/B and it stayed in for the duration of the flight. I chose not to reset the right NO1 C/B. When I reset the Left No 1 C/B the cockpit lights came back one but the EFIS displays would not come back on and only displayed 'DPU FAIL'. I [advised] ATC and had one of the med crew come up front with me to read the checklist of items that would be affected if the C/B popped again; and to assist with any other potential unknown circumstances that may arise.
Beechcraft King Air 200 pilot reported losing the No. 1 right bus; followed a few minutes later by the No. 1 left bus; which resulted in loss of EFIS and cockpit lights.