Now, the math.

Replacing all 70 of the 60-watt bulbs will, in theory, reduce the 2000kWh/year to approximately 500kWh/year. This is a savings of approximately $153/year.

Now, the standard price tag on these bulbs is roughly $60/bulb. So to replace 70 of them is an investment of $4200. This cost, divided by the annual savings, $153, equals approximately 27.45. This is the number of years it will take for your savings to equal your investment. After that point, the investment turns to profit. However, this is greater than the expected lifespan of the bulbs (20 years, a savings-to-investment ratio of about 0.7:1), meaning you'll have replaced most, if not all of them, by the time this happens, and that you won't actually profit from the investment.

Now, let's say you purchase the bulbs at the "discounted" cost described in the Yahoo! Finance article linked at the bottom of this blog, $22. You've now only invested $1540 for the same annual savings of $153. 1540 / 153 = ~10.07; about half of the expected lifespan of the bulbs. At this rate, your savings-to-investment ratio is nearly 2:1. That's 100% profit, just by changing out some light bulbs. Now take into account the fact that in this 10-20 year period, utility rates are only going to rise, and it's obvious that the investment becomes more worthy over time.

In conclusion, while the investment's not worthy at $60/bulb right now, it may very well be worthy as the cost falls, utility rates rise, and as the phase-out of incandescent light bulbs progresses.

**EDIT:**

Mind you, this is also assuming that the bulbs will actually last 20 years each. Depending on usage and misinformation (considering the bulbs haven't been out for 20 years, we can't know for sure that they will last that long), their lifespan is really unpredictable, and they may not last anywhere near 20 years. However, in the example above, so long as they do last longer than 10 years (and were purchased at the discounted rate of $22), the homeowner would remain in the black.

*-Jesse M.*Reference:

http://finance.yahoo.com/news/rebates-cut-price-60-led-222118250.html