T5 fixtures are one of the best grow lights there are, because you can use them as additional lighting or as full on artificial lights to grow plants from vegetables to flowers. But even if you own the best T5 lamp, some of the parts of it can fail. Usually the first thing that goes is either the bulbs of the ballast. Luckily, you can easily purchase both of these parts and replaces them yourself, too. But if you can easily decide on which replacement bulbs to buy, because the real decision in this case will be weather you need 6,500 Kelvin or 3,000 Kelvin bulbs, that will be determined based on what purpose your bulbs will serve, it is harder to purchase the right ballasts for your T5 fixtures and your needs. So let’s look at the main things you need to consider when you are searching for new T5 fixture ballast.
The first thing to consider probably is the light output of your bulbs, and therefore what light output your ballast will create using the bulbs that you have bought. If you have bought any kind of bulbs in your life you will probably know that the lumen output a.k.a. brightness of the bulb is written on the packaging of the bulb, because that is one of the deciding factors for most people, when they are buying new light bulbs. However, this output is measured when the bulbs are used with a normal output (NO) ballast. So if you want the exact output that is written on the packaging you should buy Normal Output (NO) T5 ballast. But since T5 fluorescent grow lights are capable to actually create higher light output while burning the same amount of watts, I would suggest you looking at a high output (HO) ballast, because the light that your fixture will give out will be brighter than the lumen count written on the packaging of the bulbs.
This should go without saying, but you need to tailor your ballast to the bulb type you are using. Even if T5 bulbs are a newer and better version of T8 bulbs, they cannot be used with T8 fixture ballast or any other fluorescent lamp ballasts, because this combination won’t work. The same goes for using a ballast meant for 24 inch or 2 feet bulbs with 46 inch or 4 feet bulbs and vice versa, because that won’t work either. So if you are T5 fixture enthusiast, then buy a ballast that is labeled as F54T5 ballast for 4 feet bulbs (their wattage is 54 watts), or F24T5 ballast for 2 feet bulbs (their watt consumption is 24 watts). But if you are using T8 bulbs then search for a ballast that has T8 in its title.
And lastly what you need to consider regarding fluorescent lamp ballasts is also the method of starting, because if you purchase a ballast with the wrong starting method it will burn out quickly and you will have to purchase new one again. The two main types of T5 light ballasts to choose from for T5 grow lights are the instant start ballasts and programmed start ballasts. The difference between them? The way the ballast lights up the bulb once you hit the on switch on your lamp. Instant start ballasts, like you can imagine based on their name, will light up the bulbs to their bull brightness the second you turn on the light, by hitting the T5 bulbs with about 600 volt current each time. So they are great if you instantly need the full brightness of the bulbs. However, that also has a downside – the fact that each time you turn on the lamp the bulbs get a shock of that many volts, their lifespan shortens each time it is turned on. So if you need bulbs for places like your grow room or living room, for example, these will be great, because in this case you probably won’t turn the lamps on and off 100 times a day. Opposite to these ballasts are the programmed ones, which instead of hitting the bulbs with full force, heats up the cathodes in bulbs slowly and steadily, that way letting the lamp slowly reach their full brightness. That also means that the lifespan of the bulbs will be longer and they will be more susceptible to frequent on/off switching. So if you need a ballast for T5 lights that are placed somewhere, where you will be turning the light on and off many times a day, then go with the programmed start ballast.
Ballasts are small and cheap (ballast usually costs under 20 dollars) yet curtail part of any lighting fixture, and T5 fluorescent grow lights are no different. So choose the best ballast for your T5 fixture, so your lamp can work to its maximum capacity and emit the maximum amount of light.