I still had the old type tubelights over here in my village with chokes. So whenever the voltage is low, they just fail to switch on.
I wanted to ask you about it as you mentioned this issue earlier as well. Does your tube flicker when you switch it on, regardless of the voltage? If yes, then you've been using something which was outdated at least a decade ago. We started using electronic ballasts from 2002. Since then, the tubes would just switch on like bulbs - no flickering - instant on. But in hilly areas, we had to use voltage stabilizers till 1998.
We moved to 28w tubes in 2009~10. And from the last 2 years, we started to replace dying 28w florescent tubes with 19w LED tubes. The important thing to notice is that we were 'forced' to buy LED tubes because people stopped stocking ballasts for T5 tubes in my area! we never wanted to invest in costly LED tubes as a T5 ballast for Rs 100 would've just worked fine.
You'll find LED bulbs everywhere because they take less storage in shops and yield more profits for the shop-owners. T5 florescent tubes are so ungainly and LED tubes are probably too costly for people in your area.
How low can LED handle, the tubelights & CFL's can handle as low as 150V.
It all depends on the quality and type of the driver circuit. I've seen 5 drivers going bad but only 3 LEDs in the last 4~5 years. These were not 3 bulbs as whole the actual tiny 1w LEDs grouped inside. i just soldered new LEDs and never had to replace the whole unit. i have concealed/flushed LEDs with separate driver units and heat sinks.
I make my own LED drivers as well. In my case, a 2w LED on homemade driver lasted 1 year of continuous operation. All the lights and low power devices in my house are connected to inverter; so this was truly a non-stop operation. Mine was a constant voltage driver but if you use a constant current driver, then you can really use the LEDs for their full lifetime.
LEDs need constant current to operate at their best luminosity. In short, use constant current driver when you know how many LEDs you have and in which configuration (series or parallel). When dealing with arbitrary numbers (e.g., in strips), it's better to use constant voltage driver.
So, to answer your question, LEDs can handle low voltages pretty easily because they always get the same amount of voltage/current from the driver. This driver is just like your laptop charger - which can operate on low voltages and safeguards the laptop in case of fluctuations etc. Infact, you can use safely your 12~15VDC laptop charger to power LED strips. LEDs need DC. AC LEDs may take time to become commonplace.