[Binare]

I'm an electrician and my best advice to you is not to change 1 bulb at a time, change all the bulbs on a ballast. If you have 2 ballasts with 2 bulbs burn out... Change both on that ballast not just the one. By changing one bulb only you are reducing the life of the ballast and both bulbs due to harmonics, applies to electronic and magnetic ballasts. Something else to consider is one of the greatest advantages of t5 is there effiency. A t5 bulb will only lose on average 5% of its effiency when it finally burns out. Changing a t5 every year is like flushing money down the drain. Mine are 3 years old now, measured with a par meter from work about 7 months ago and I had only lost between 1% and 6% across the 4 bulbs I have.