If you can provide more details on that data you are seeing in the monitoring app for production and consumption versus the consumption from your utility maybe we can help. Also, please provide details on your PV system, such as the total PV array size in kW DC, what size inverter you have in kW AC, and general location (City and state would be fine) and the array orientation, such as "mounted on 28 degree roof, facing 20 degrees east of due south" or something like that. Also, if the array is shaded by nearby trees at all, and if so, approximately what time of day the shading occurs, such as "before 10am" or "after 5pm", etc.
For any conversation about performance, I always like to make sure the proper terminology and units are used, so that there is no misunderstanding. So here are basics.
1. Power is an instantaneous measurement, with units Watt (W) or kiloWatt (kW). 1000W = 1kW.
2. Energy is Power used over time, with units kiloWatt-Hour (kWh). 1 kWh = 1000W used for one hour. Energy is what your utility charges you for. Typically 1kWh cost between $0.11 to $0.22 depending on where you live.
3. Production, consumption, import, and export can refer to either power or energy, depending on the context, so it is important to describe in the discussion.
4. Production (Energy) is the number of kWh your inverter produces in a certain period, whether hourly, daily, monthly, etc. Production (Power) is the number of kW your inverter is producing at a certain point in time.
5. Consumption (Energy) is the number of kWh used in your home over a certain period (hr, day, month). It can also refer to the instantaneous power being consumed in the home kW at a certain point in time.
6. Import (Energy) is the number of kWh brought in from the utility grid to serve loads in your home over a certain period. It can also refer to the instantaneous power flowing from grid to your home at a point in time.
7. Export (Energy) is the number of kWh sent out to the grid from your home, which is possible because your have a solar generation system installed which is am energy source. You can also refer to export of instantaneous power at a point in time.
8. The numbers for the above can be known by measurements and by calculations. Production is directly measured and reported to the monitoring system by the inverter. In order to measure import and export, sensors (usually current transformers) are located at the service conductors that connect your main service panel or main service disconnect to the utility meter, and the sensors are connected to a meter installed with the solar that use the measured current (Amps) and the measured voltage (seen by the inverter) to calculate power and energy. If the service conductors are not instrumented, then your monitoring system can not know how much energy or power is being imported from or exported to the grid. Consumption can be calculated by adding the import number to the production number, and subtracting the export number. For example, if in a day you imported 10kWh, and the solar produced 20kWh, and you exported 5kWh, then the energy consumed in the home for the day was 10+20-5 = 25kWh.
I know many people know the above and I apologize for the long boring and basic explanation. But any time there is an effort to look at monitoring data and utility bill data and use it to determine if something is not operating properly, it is important to make sure the data is complete and understood. There are a few things that are fairly common to mess things up. First, sometimes the CT's that do the import export measurement are installed backwards (one or both). Second, sometimes the CT values or the meter itself are misconfigured in the inverter.
If all the data is good, the import data should match what the utility shows for usage, as long as you are looking at the same time frame. There should also be a second counter on the utility bill that usually is labeled "kWh out" or "export". This counter should match the export value in the monitoring system. The utility should charge you the difference of Import - Export, or the net usage, if you have a net metering agreement with them.
AviSun Renewable Energy
Sent: 01-28-2023 06:34 PM
From: YEHUDA GRABLI
Subject: Issues With My solar System Help
Greetings to community and members,
I am in search with help/similar experience with a residential system that was installed by Sunpower.
We got our system installed last September and since then we are being charged by the utility as well.Upon carefully checking, all data by Sunpower monitor and App for production and consumption just don't make sense and are not aligned with Edison our local energy utility company.
Numbers just don't add up.
We contacted Sunpower so many times about this issue and even refuse to pay for the finance company till system is working properly.Sunpower keeps sending a technician,from a third party ,who really can't resolve the issue.
I would like to proceed at higher ways.Looking to get help and ideas via this open channel.