Tariff Calculation
I'm implementing some utility tariffs in EnergyPlus and then checking them in Excel to see if I'm using the EnergyPlus objects correctly. Unfortunately, I'm getting 2%-5% off on the $ amount in my Excel sheet than what EnergyPlus is coming up with. The tariffs are a little complicated, so that could be an error in my Excel sheet instead of EnergyPlus.
Another strange detail is using MJ units versus Therm units for the tariff seems to be much much more accurate for a flat rate tariff. I'm having to go through, translate, and then test my more realistic tariffs to see if that carries through though.
But before I do all that work, I wanted to ask if other people have experienced it. Is this a known issue? There's a couple other posts on this, but I'm waiting on posting of their calculations. If not, I'll document my IDF objects, EnergyPlus outputs, and Execl calculations and update the post.
POST SCRIPT
Silly me. I made a season schedule for my tariff, but I didn't add the schedule to the UtilityCost:Tariff object. To help others, I could have easily noticed this by looking at the Charges subtable in the HTML output file with the TariffReport in the Output:Table:SummaryReports object.
There was also a warning in my ERR file, which I didn't even look at.
** Warning ** GetInputEconomicsChargeBlock: UtilityCost:Charge:Block="GASWINTERBLOCK" invalid data
** ~~~ ** Season="WINTER".
** ~~~ ** a Season other than Annual is used but no Season Schedule Name is specified in the UtilityCost:Tariff.
** Warning ** GetInputEconomicsChargeBlock: UtilityCost:Charge:Block="GASSPRINGBLOCK" invalid data
** ~~~ ** Season="SPRING".
** ~~~ ** a Season other than Annual is used but no Season Schedule Name is specified in the UtilityCost:Tariff.
** Warning ** GetInputEconomicsChargeBlock: UtilityCost:Charge:Block="GASSUMMERBLOCK" invalid data
** ~~~ ** Season="SUMMER".
** ~~~ ** a Season other than Annual is used but no Season Schedule Name is specified in the UtilityCost:Tariff.
** Warning ** GetInputEconomicsChargeBlock: UtilityCost:Charge:Block="GASFALLBLOCK" invalid data
** ~~~ ** Season="FALL".
** ~~~ ** a Season other than Annual is used but no Season Schedule Name is specified in the UtilityCost:Tariff.
Looks like there's a $14 difference between my Excel calculation and the EnergyPlus output, but they cancel out. I'm guessing DST has something to do with it, but the sum is what really matters.
Excel EnergyPlus
Month Charge Annual Charge Month Charge Annual Charge
1036.908471 7198.925131 1036.91 7198.93
1275.551854 1275.55
960.0292933 974.05
758.3005312 758.3
62.12539822 62.13
0 0
0 0
0 0
13.24609827 13.25
590.7892087 576.77
883.6610168 883.66
1618.31326 1618.31
@mldichter please post your IDF file, outputs and excel spreadsheet so that I can try to figure out why you are getting different results.
@JasonGlazer Sorry for the delay. Here is a google drive link to one of the tariffs. This one has four seasons with a different baseline gas therms in each. The total USD amount isn't too far off, I think ~1%, but the months vary quite a bit. The total error also seems to get worse if you add in a Minimum Monthly Charge in the UtilityCost:Tariff object. My minimum was $71.01 per month, which gave 2%-5% monthly errors. I wasn't sure about my hand calculation though, so I took it out of the linked IDF.