2-3 hours with 125 watts is essentially useless in most circumstances. Just letting you know. And if you're going to suppliment and pay the cost for a fixture, it'd make more sense to run it longer using a less powerful bulb than to run it for so short a period of time.
Okay, let's look at what you'd pay over 50,000 hours of usage. Now, you might do 50,000 hours over 6 years with 24/7 usage, you might do it over 25 years with using it about 20% of the time (partial winter supplimentation)... however you do it, the math works out the same (unless we want to get complicated and factor in interest and inflation and depreciation and the like
). And if your response is "I'm not going to use it 24/7 or even 20% of the time", see the above paragraph. I mean, you *could* just point a 5W flashlight at your plants for 5 seconds each day, but that doesn't mean it's a meaningful endeavour
The total amount of light energy has to be sufficient to matter or it's pointless.
Such a bulb probably has a lifespan of about 20k hours. So 5k hours is 2 1/2 bulbs. Fixtures don't last forever either, but let's be generous and say 50k hours. 50k hours is what you'll get out of a single good LED fixture (no separate bulbs). Let's assume the fluorescent fixture costs 600 Kč. So, 700 Kč * 2,5 + 600 Kč = 2.350 Kč
Now for power. 125W for 50000 hours is 6.250.000 watt hours, or 6250 kWh. Times 4,53 Kč is 28.312 Kč. Adding these numbers together, your total costs are 30662 Kč.
Note how vastly more expensive power is than the fixtures and bulbs over their lifespan.
Now, you could get an LED. 125W fluorescent is pessimistically 70W LED or so. The best Ebay prices of chinese-made LED fixtures are about 1,15 USD per true watt (LED fixtures are often listed in "rated watts" or similar which are double the actual consumption, LEDs are run at about half power to greatly extend the lifespan). Let's say you pay three times that due to taxes, shipping, more expensive manufacturers, or whatnot - 3,45 USD per true watt, aka 67 Kč. So 67 Kč times 70W is 4690 Kč.
So yeah, it's a lot more expensive than one bulb. It's even more expensive than 2 1/2 bulbs and one fixture. But what happens when we factor in power? 70W * 50000 hours is 3.500.000 watt hours, or 3.500kWh. Times 4,53 Kč is 15.855 Kč. Plus your fixture cost, that's 20.545 Kč
So let's compare everything side by side:
Fluorescent: 30.662 Kč
LED: 20.545 Kč
But that is of course with pessimistic figures. Let's say you pay only 50% more than the best ebay prices, and you only need 50W LED to compare to that fluorescent bulb. How does that change the results?
Fluorescent: 30.662 Kč
LED: 13.029 Kč
See the difference? And notice how the real costs are in power?
But let me reiterate, 125W fluorescent for 2-3 hours is virtually meaningless unless the area is tiny. How much area are you talking about illuminating? I can look up online how much sun you'll be getting - are they in full sun all day, or are there any obstructions? I'd like to be able to give you a sense of how much power you'd actually have to run to make a meaningful difference versus just that which comes from the sun.