Case Study 1: Net Energy Metering (NEM) on-grid solar system
Location : La Honda, California, USA
Year : 2019
Figure above shows a real data of the typical NEM energy production monitored hourly from on-grid solar system. The y-axis shows energy production, whereas the x-axis shows the time from 12 midnight to 11PM. The blue line is the imported energy from the power utilities to the house and the red line is the exported energy (the excess energy) from the house to power utilities. The blue energy export line (excess energy) is calculated after you have subtracted your generated solar energy with your home appliances energy consumptions.
As sun rises at 7AM, the solar system generated energy steadily and produced peak power at 2PM. Then, the power generation reduced steadily until sunset at 7PM. As for the energy import line (red) it can be seen that from 7AM to 7PM there is no energy imported from the power line because the solar panels generate excess power during the day since the homeowner is at work. When the sun is set, the solar panel does not generate electricity. From the graph, the red line is steadily increases from 7PM to 11PM. This is due to the fact that the homeowner is back at home and having activities such as cooking, washing, drying clothes and cleaning up. As the homeowner is getting ready to go to bed this means less home appliances are been used. Hence, less energy is being imported from the power line from 11PM to 7AM.