HOMER Knowledge Base
Understanding the Calculations Inside HOMER Grid
Product: HOMER Grid 1.2.1
In order to better understand the calculations inside HOMER Grid, let's walk through a simplified example. The file we are using in this example is “Peak Shaving Simple Example.hgrid”. First, we will walk through the model inputs. Next, we will take a closer look at the utility bill calculation, the peak shaving algorithm, and finally, how the economics are calculated.
To begin, start by opening the sample file “Peak Shaving Simple Example.hgrid” found in the Samples section of the File menu shown below.
The load profile is a flat 100 kW load most of the time, with four hours every day at 200 kW. There is no variability added to the load, so it is the same every day. The total consumption is 2800 kWh per day.
The utility rate was created with the “Build Tariff” tab of the Choose Utility pop-up window (accessed by clicking the “+” button next to the word Tariff). The $0.10/kWh consumption charge is listed in the Tariff menu under the Consumption tab.
The Demand tab shows the $35/kW demand charge.
By clicking the “Tariff Bill” tab on the right side of the Tariff menu, we can see the predicted monthly bill. By hovering the mouse over the bars, we can see that the demand charge is $7,000 each month ($35 times the 200 kW peak). The energy charge depends on the number of days in the month. Months that have 30 days cost $8,400, those with 31 day are $8,680.
In order to better understand the calculations inside HOMER Grid, let's walk through a simplified example. The file we are using in this example is “Peak Shaving Simple Example.hgrid”. First, we will walk through the model inputs. Next, we will take a closer look at the utility bill calculation, the peak shaving algorithm, and finally, how the economics are calculated.
To begin, start by opening the sample file “Peak Shaving Simple Example.hgrid” found in the Samples section of the File menu shown below.
You can view the load profile by either clicking the critical load icon in the schematic or Critical, listed under the Electric Load tree.
The load profile is a flat 100 kW load most of the time, with four hours every day at 200 kW. There is no variability added to the load, so it is the same every day. The total consumption is 2800 kWh per day.
The utility rate was created with the “Build Tariff” tab of the Choose Utility pop-up window (accessed by clicking the “+” button next to the word Tariff). The $0.10/kWh consumption charge is listed in the Tariff menu under the Consumption tab.
The Demand tab shows the $35/kW demand charge.
By clicking the “Tariff Bill” tab on the right side of the Tariff menu, we can see the predicted monthly bill. By hovering the mouse over the bars, we can see that the demand charge is $7,000 each month ($35 times the 200 kW peak). The energy charge depends on the number of days in the month. Months that have 30 days cost $8,400, those with 31 day are $8,680.