With the recent explosion in LED lighting alternatives, and living off-grid where power use is a concern for me, I've been noting the appearance of the LED "Tubes" compatible (allegedly) with magnetic rapid start ballasts. (Electronic F32T8 replacements have been around for a few years now, but around here the "t12" replacements are just now showing up in Home Depot, etc. 

Anyone have any insight into the electrical characteristics of these funky plastic abominitions and how older ballasts, or the cheap low-power-factor residential ballasts, might fare with these?  I have both HPF and NPF ballasts in use and many of the NPF ones I couldn't care less about, i.e if they burn up I'll just buy direct-wire tubes, but how would these treat a HPF ballast, particularly those which don't necessarily like 34-watt "energy saver" lamps at all? 

With the recent explosion in LED lighting alternatives, and living off-grid where power use is a concern for me, I've been noting the appearance of the LED "Tubes" compatible (allegedly) with magnetic rapid start ballasts. (Electronic F32T8 replacements have been around for a few years now, but around here the "t12" replacements are just now showing up in Home Depot, etc. 

Anyone have any insight into the electrical characteristics of these funky plastic abominitions and how older ballasts, or the cheap low-power-factor residential ballasts, might fare with these?  I have both HPF and NPF ballasts in use and many of the NPF ones I couldn't care less about, i.e if they burn up I'll just buy direct-wire tubes, but how would these treat a HPF ballast, particularly those which don't necessarily like 34-watt "energy saver" lamps at all? 

Hello If you want to replace T12/T8 fluorescent tubes with LED better is to buy models which required hot and neutral on one side without ballast.You will have lighter fixture and save money.

As most of the US ballasts, are rapid-start, with very low OCV (~200V), it is possible to produces LED tubes that operates directly from these ballasts, so it is less expensive.
As we uses series chokes and starters, we needs to bypass the ballast for the LED tube, and this is more expensive.

The problem is, you can not design any retrofit to be really 100% compatible with any ballast (and mainly for the F40T12 the ballasts were varyinng really a lot among the different types), unless the retrofit would have the same characteristics, so thenthe same input power as the original tube. But that would eliminate the original idea - saving power without the need of any change in the fixtures.
 There are few types designed to be directly plug-inreplacements for the fluorescents,but these assume only certain ballast characteristics, so arecompatible only with some ballasts.
Majority of LED tube retrofits are designed touse just the sockets and fixture body from the original setup, but are supposed to be wired directly on the mains without any ballast. The reason is, the 120VAC voltage source is way more standard than what the ballasts use togiveoff.
The problem with ballasts is,these need to be designed asahigh impedance sources, delivering the desired current into a load which tends to dictate the voltage. In that, the only theoretically clean way to reduce the power is to force lower voltage. This was the way the 34W flourescents were designed,but the experience was, many ballasts just overheat because of the lower load voltage. The even lower voltage that would be inposed by the desired LED retrofit would be expected to be evenworse ballast killer. So although the lower voltage is inthe theory a clean way, due to real life limitations it is not usable.
The method most designs use is assuming the RS OCV uses to be around 230V, so they are designed for that voltage andto drawlow current, so operate the ballasts near the open circuit state. But there is one big problem: Themajority of ballasts may be giving off about the 230V OCV, but there are many ballast types designed to giveoff significantly higher OCV (to havemore reliable starting, for coldertemperatures,...). And that voltage may beway too high for theretrofit and just kill it.

So the best thing to do when you want to go the LED way is to really install some decent quality LED lanterns from some reputable source (where you will be able to get replacement modules).
If you really want the fluorescent retrofits, use the types intended to operate directly at the mains without the ballast.

There are even types, where the pins at the tube ends are used just for mechanical support andthesupply is wired separately,via separate cable and connector. These allow you to avoid any compatibility issues, while still go backto the original fluorescents if you decide so after some time. But these are not that common and are likely more expensive.

Or just ignore LEDs and stay with the fluorescents, just choose the high efficacy models and use either lower ballast factor ballasts (when you want less intensity, better space spread light, mainly with bare tubes) and/or fewer tubes (themost efficient way, but some fixtures may become glary when fitted with higher output lamps than normal.

Some LED tubes have the pins on either end shorted together (for use on Switchestart without starter), or the pins on one end being the power input and the other end being shorted (for use on Switchstart with shorted starter). Any of those would short out the cathode heating windings of RS ballast, so quite readily destroy the ballast. Measure continuity between the pins before putting anything on a RS

I currently have a light with a 2xF40 LPF RS ballast that has 1 F40 + 1 LED retrofit tube - 'UltiTech Pro' brand (the standard 'UltiTech' ones won't light on a RS ballast, but this one does - even though it says electronic ballast only)...what I don't know is how it affects the ballast - if it'll overheat or anything (the shelf that said light is attached to is going to be moved to another room, so when I remove the lights to do that I'll have the fixture sitting around & plan to do some tests with the kill-a-watt meter)

I've done it, 120 through 277 volt lamps work best.

I read elsewhere the electrical characteristics (on HPF anyway) should be close to open circuit/no lamps installed, versus overheating a ballast with excessive lamp current.

Given this, would such LED tubes theoretically be OK on preheat ballasts?  I'm seeing some now that say they should be, with no starter needed.

If the lamps are close to open circuit, they gotta be ok. The exception i see is with SRS- and SR- like ballasts, that would run the ballast at a mode where significant current goes through the LC circuit, tha ballast may be overheating and the capacitor may be subjected to overvoltage (a condition that happens only briefly with the proper lamp installed)

Also, a thought : RS ballasts supply heating current to filaments, so the LED tube must not have shorted pins. In Preheat it's opposite : There is no rule which socket contact in the luminaire is the supply and which is the starter loop, so LED tubes made for retrofits on Preheat gear (of the supply from 2 ends type) do have shorted pins, and instruction to remove the starter, so they could get the power from either pin. It is possible to build a tube that will work ok in both ballast types and not short the RS heating supply, but most of them are not, and considering how the LED retrofits market is a mess, it is risky to assume that if a tube states it can work on RS ballast then it really can. (even if it was tested, the test could be as little as powering it on RS ballast for a few seconds to see that it works at all, but not checking what else it does)

Please don't use these LED tubes unless your ballasts are disposable and unimportant. I tried one, destroyed the ballast, never will I attempt such a retrofit again.

Some strip lights I bought from restore last year came with LED tubes on them, and they were running off the universal F40T12 ballasts, one of which had a completely dead cap and was running as a LPF ballast... guess the tubes were to blame on that one. They are the  LED tubes that were made for magnetic though

The easiest LED retrofit is to install tubes that are wired directly to supply voltage (120V etc.) where the hot lead goes to one end and the neutral goes to the other end. I recomend these to my clients.

The easiest LED retrofit is to install tubes that are wired directly to supply voltage (120V etc.) where the hot lead goes to one end and the neutral goes to the other end. I recomend these to my clients.

I think same.I had LED tube which was connected directly on mains.