Tiered Energy Rates -- SAM treats daily as monthly?

When using SoCal Edison Tiered electricity rates -- downloaded in the "Electricity Rates" tab in Photovoltaic Solar -- SAM seems to treat the daily rate tiers as monthly. Is there a fix for this?

Example:
Tier 1 Max Usage = 11.1 kWh
Tier 2 Max Usage = 14.43 kWh
Tier 3 Max Usage = 22.2 kWh
Tier 4 Max Usage = 1e+038 = infinity, basically.

So each day, the first 11.1 kWh are tier 1, the next 3.33 kWh are tier two, the next 7.77 kWh are tier 3 and the rest are tier 4. PER DAY.

But SAM does this PER MONTH. So in a month with 900 kWh use, the first 22.2 kWh goes to tier 1-3, then the remaining 877.8 kWh goes to Tier 4.

What is the fix?
I could just multiply the tiers by 30 days (or better 365/12 = 30.417 ) but then that means the model assumes that every day in the month has reached the Tier 1 limit, when in reality some days do and some don't.

It seems like SAM generates a varying daily energy use in the model. Am I missing something... is there some box I am supposed to check to use Edison's DAILY TIER LIMITS correctly in SAM?

Thanks,
Tim

Paul,

First off -- thanks for your reply and for your help. SAM is a great tool!

Second Question First:
2) "What rate structure?": I am using "Domestic Service: D - Baseline Region 13" from Southern California Edison Co (www.sce.com/NR/sc3/tm2/pdf/ce12-12.pdf). I am inputting Monthly Load Data into the "Calculate Load Data" on the "Electric Load" tab. (Photovoltaic Solar)

What is loaded into SAM when I select this rate structure is a set of DAILY TIERS (11.1kWh, 14.43 kWh, 22.2 kWh, etc). So then when SAM does the calculation of electric cost without system, it puts like 97% of energy use into the highest tier for the month. Example: If I use more than 22.2kWh on the first day of the month, then SAM calculates the rest of the month's energy use at the highest rate, rather than "resetting" on the next day to start with the lowest tier.

An approximate solution is to multiply the daily tiers by 30 to give a "monthly tier" -- but Edison calculates the use costs daily, not monthly, I believe. So it isn't perfect, but it gets closer.

1) "Varying Daily Energy Usage": By that I mean that SAM seems to use a model that simulates energy use that is varying from day to day WITHIN the Electric Load Data that I provide.

Example: Lets say that in April I input 600 kWh of use. SAM does not assume that on every single day I am using 20 kWh... rather, SAM assumes that some days I use more, some days I use less. SAM generates an electric use profile for the month (Simulate > Time Series > Hourly Data > Electricity Load (Year 1) (kW)). That profile has a bit of randomness to it.

Thanks again for your help. Please let me know if any of this is unclear or if I can provide any additional info.
I appreciate your time and assistance,
Tim