Imports, Exports & Non-Bypassable Charges
Imported Energy measured in kWh, is energy that is consumed from the grid. During the day when the sun is shining, imported energy would occur when the facility is using more energy (kWh) than the PV system was generating.
Exported Energy, measured in kWh, is energy that is back-fed to the grid. In other words, the solar system was producing more energy (kWh) than the facility was using, during a given interval.
Calculating the ‘avoided cost’ or ‘value of solar’ requires calculating how much energy (kWh) gets exported to the grid. On the ‘Edit Proposal’ screen, users can reference how much energy is exported in % terms inside the ‘Meters’ section.
Note: Energy Toolbase can only accurately calculate exported energy if a user references an ‘Energy Use Profile’ that has interval meter data. If you reference an ‘Energy Use Profile’ using monthly summary data, we simply assume that inputted kWh energy usage is evenly distributed throughout all intervals in a billing cycle. Therefore, the exported energy value we calculate using monthly summary data is not a good indication of exported energy.
Non-Bypassable Charges (NBC’s)
NBC’s are volumetric based ($/kWh) charges that a customer must pay on all energy they ‘import’ from the grid. In other words, these charges cannot be offset by solar exports to the grid. Therefore:
- Solar customers pay NBC’s on all imported energy.
- NBC’s cannot be netted out or offset by solar exports.
- The value of solar exports gets discounted by the ($/kWh) NBC rate.
How does Energy Toolbase calculate & display NBC’s in the Energy Use Profile?
We insert an ‘NBC’ column into the Energy Use Profile table. The “NBC” column calculation =
gross imports * NBC rate ($/kWh)
The ‘Energy’ column of the Energy Use Profile table changes. It’s no longer net usage * full retail rate. The “Energy” column calculation is now =
net usage * (Full Retail rate – NBC rate)
Here’s an example:
- Assume the full retail volumetric rate of energy is $0.20/kWh.
- The user selects the “Net Billing” option and sets the NBC rate @ $0.025/kWh.
- When solar reduces imports (but does not export to the grid) that production gets valued at the full retail rate of $0.20/kWh.
- When solar exports to the grid (more energy is produced than consumed in an interval), those exports effectively get valued at $0.175/kWh. Because solar exports do not offset the $0.025/kWh NBC charges.
*This calculation and display should properly account for the effect of NBC’s for any type of project.