G of CO2 per kWh from burning methane

[Archosaur]

http://europe.theoildrum.com/node/6638" has a chart that claims that the burning of methane yields 360 g of CO2 per kWh of energy released. I decided to check that, but I'm not getting the same answer they suggest. Here's what I did:

CH4 + 2O2 = 2H2O + CO2
-74.87 + 0= 2*-285.83 + -393.509
= -571.66 + -393.509 +74.87= -890.229 kJ/mol

(all standard enthalpies of formation came from wikipedia)

CO2 is 44.011 g/mol
890.229 kJ is 0.24728583333 kWh (significant figures be damned)

44.011/0.24728583333 ≈ 178 g/kWh, as opposed to their 360 g/kWh


I can't help but notice that my answer is suspiciously close to a factor of 2 off... but my eq. is balanced...
Can someone tell me what I've done wrong?

Thanks

 

[cesiumfrog]

You say per kWhr of heat, but their graph says per kWhr of electricity.

 

[Archosaur]

*slaps forehead

I figured I'd be kicking myself.
Thanks, cesiumfrog.