NRG and Owner's earning

Definition of Owner's Earning:
net income plus depreciation and amortization, minus capital expenditures and change in working capital

Here is half year calculation for NRG (2006):
net income = 229m
depreciation and amortization = 308m
capital expenditure = 74m
Owner's earning = 229 + 308 - 74 = 463m
(assuming no working capital change)

Half year PE ratio = 6890/463 = 14.9
One year projected PE ratio = 6890/(463 * 2) = 7.4

所以这股票是很便宜的，但仅从GAAP PE ratio看不出来。这公司准备在两年内用750M cash买回自己的股票 （http://biz.yahoo.com/bw/060801/20060801005497.html?.v=1），所以我觉得公司股价长期前景看好。