Monthly Electrical Cost incorrect

I'm doing a simple PV system analysis and my numbers are not adding up.
My Yearly Electrical cost is off by about $1300/yr. I'm using actual hourly data directly from PG&E billing, and also updated the Utility Rate schedule for Tiered Energy Rates (way off from openei).

I can get the monthly charges "close" if I check mark "Enable net Metering" but my monthly costs are way out. Not sure what I am doing wrong..
Any help??
I've attached what my actual monthly bills are for 2013... thats the data I'm using.

From my understanding of the rate structure you are using, net metering does not apply, so I think it is probably a coincidence that the costs are close to what you expect when you enable net metering in SAM. Also, there is a bug in the net metering calculations in SAM that results in the sales/purchases value for January being incorrect (See the Download page for a list of known issues). We plan to release an update to fix this and the other issues very soon.
What is more likely to be causing the difference you describe is the "Max Usage kWh" values for the tiered energy rates. In SAM, that is a maximum hourly value. That means that in your file, the Tier 2 rate will only apply in hours when the hourly kWh from the grid exceeds 675 kWh.
I've attached a spreadsheet to your original post that shows that SAM applies the Tier 1 buy rate ($0.1323/kWh) to all hours of the year. That's because the hourly grid purchases over the year range from zero to a little less than 12 kWh.
Is it possible for you to recalculate the Max Usage kWh values for each tier to be maximum hourly values?
Best regards,

Paul.

Thanks Paul,
I'm somewhat following you other than the recalc for maximum hourly values.. My understanding is that 675kwh IS the maximum hours @ the .1323/kwh rate(Tier 1,Period1).. + 877kwh-675kwh=200kwh @ .1504/kwh (Teir 2) I also do not see a spreadsheet attachment. Maybe that would clear me up.

The spreadsheet should be attached now -- sorry about that.

I'll have more on this after I've consulted with the developer.

Thanks,
Paul.

I believe I understand now.. The tiering is based on per/Hour usage in SAM, that is the problem. Pg&e bills a monthly interval BASED on an allowed per day kw usage (22.5kwh) for tier 1 but it gets spread out over a month period.. I don't know of a way to fix this .. I re-entered the Tiers based on a per hour rate, (22.5kwh/24=0.9375 per day for Tier 1, etc... I got a little closer but now it estimates higher bills due to looking at an hourly rate as apposed to a monthly. Maybe a future version can change the billing period khw max intervals by day, month, hour, etc.. Let me know if I'm understanding this wrong. Sounds to me PG&E is making this as about as hard to understand as possible.

Yes, your understanding is correct. For the next version of SAM (Fall 2014), we plan to fix the tiered rate model so that it accumulates kWh's over the period you specify (Period 1, 2, etc.) instead of hourly.

Best regards,
Paul.