I can't actually see any great difference in brightness between the Tesco 15W bulb and the 100W normal one next to it. If anything the energy saver is brighter. They're rated at 10,000 hours life so if they get anywhere near that they're about the biggest bargain of the year. The 100W bulb is now coming back out immediately and going into the stockpile. I just wish I'd bought 10 of the things instead of 5.
I'd been grumbling about the government banning incandescent bulbs but at 34p a shot for energy savers that last 10 times longer that's me converted. Better fill your boots before Tesco put the price up. I reckon I've been spending £10 a year on normal bulbs plus the much bigger electricity cost they've been wasting. They don't last very long and I usually buy packs of five and seem to need a new pack every couple of months.
I've just written a spreadsheet to see what these will save. If you have 5 bulbs on for 8 hours a day, swap 60W normal bulbs for these, normal bulbs cost 60p each and last 1000 hours and electricity is 12p a kWh you'll save £87 a year. £79 in electricity and £8 in bulb costs. For the whole country that's nearly 2 billion quid a year. Even more interesting, playing with the spreadsheet, your break even cost would be the same if the energy savers cost £60 a bulb. Anything less than that and you're winning. It rather puts into perspective the £5 a bulb these things have cost in the past and which has no doubt put many people off using them. At 34p each it's a no brainer.