... of the led lighting ,but the cost is only one half of the led ,it will open ... can remains 80% brightness luminous maintenance and reduce only 10% lighting efficacy after using 3 years . ... PIA : > 4yearsCosmoPolis HID-PV Xtreme electronic ballast :only 10% efficacy lost after working 60,000 hours -wholly ... light output.But the sodium street lamp can only withstand 3% voltage fluctuation and unstable light ...