Tentative: won't work

Bad news. Calculations based on 11 reactions per kilowatt hour gives it cost somewhere around $40 worth of electricity to make 16 dollars worth of methane at current market prices. That may not be accurate calculation so I'll have to recheck once I get home. If that holds up this is too expensive.

Update:

I've already done this calculation once.

Here it is again, but this time from another point of view.  Verdict:  It will work unless I've made a mistake .  Now that I've checked it two different ways, the odds are less that that happened.  The worry that it won't work was premature.