Anyone who goes solar with Certasun can monitor their solar system using the mySunPower desktop portal or app from SunPower. The platform allows customers to easily track their electricity production and usage by day, month, or year.
But first-time users are often confused when they see that the numbers on mySunPower do not match the usage and export information listed on their utility bill.
Below is an explanation of how to reconcile mySunPower with your utility bill. We use a ComEd bill here as an example, but the following is true for other utilities as well.
Your Utility Does Not Register Solar Energy Used Directly by Your Home
When you go solar, your home uses the energy your solar system produces and then, if you need more (at night or on a dark day), you pull energy from the grid. The energy that your home uses directly from solar never interacts with the grid, and therefore it isn’t reported by the utility. The utility doesn’t even know it existed! For this reason, the usage reported on your ComEd bill will only include energy pulled from the grid through your meter.
On the example bill above, ‘Total Usage” is 297. This is not the total electricity usage of your home, but the total usage from the grid. Note the year-ago value, from before the customer had solar, is 522, which is 225 kWh higher than the current period. The home likely used about the same energy as the previous period. The difference was provided by the solar system, but the energy used directly from solar is not counted on the utility bill.
The utility bill also shows the excess energy that was sent from solar to the grid. In this case, the system exported 819 kWh through the meter to the grid:
mySunPower Reports Total Energy Consumption from All Sources
You can view your home’s true total energy usage in your mySunPower monitoring account. Unlike the utility bill, the mySunPower data includes the energy produced by the solar system that’s immediately consumed in the home.
For the same time period as the ComEd bill, mySunPower reports 502.3 kWh of actual energy used in the home. This is the difference between what the system produced (1,072.1 kWh) and the net of what it exported to the grid (569.7 kWh).
It’s important to be mindful of the date range when comparing your ComEd bill to your mySunPower account, as they treat the end cap dates differently. ComEd lists the date range March 1 through March 29 in this example as a 29 day period, which means they are only including one of the end cap dates. mySunPower would treat the same range as a 30 day period and would include both end cap dates. Thus, the mySunPower example above has been adjusted down one day to account for the difference.
Reconciling the Differences Between ComEd and mySunPower
An initial look at mySunPower and your ComEd bill does not immediately make clear how the two line up, but some simple addition shows that the numbers match. Simply put, the total energy flowing into your point of interconnection is equal to the energy coming out of your point of interconnection.
Flowing in: 1,072 kWh from solar + 297 kWh from ComEd = 1,369 kWh.
Flowing out: 819 kWh to the grid + 502 kWh to your house = 1,321 kWh.
The small differences in the two totals are likely due to the differences in measurement timing described above.
If you have any specific questions about your mySunPower account, you can reach out to [email protected].
