You can use a lux meter, with the light sitting across a couple of chairs, to measure the intensity versus distance from the light. Then divide the lux readings by 61 and you have an accurate enough measure of the PAR produced at that distance. This will work for T5, T8, LEDs, as long as they are in the 5000-10000K color temperature range. We don't need any more accuracy than this for deciding how to use a light or whether to use it. And, it is very much cheaper - as low as $10 for a Mastech lux meter.