This study and design involved the use of the SDG&E TOU-5 rate structure and the optimization of user consumption to best accommodate the rate selected. The parameters are as follows:
The home has 4.22 kWp of solar. This results in average daily solar production of around 20 kWh.
The home has a 10 KWh battery and a rectifier/inverter limited to 5 kW.
The homeowner owns an EV (a Tesla Model X).
As a result of owning an EV, the homeowner qualified for a variety of favorable EV rates for charging the vehicle. The homeowner also qualified for the ability to sell power back to the utility that depended on the time of production, with the most favorable time to sell the power back being during the utility peak hours of 4 pm to 8 pm.
The end result has been a house often ends up with zero electricity bills at the end of the month (its next annual “true up” is in August 2022).
This homeowner is on a fixed time of day schedule and is not currently using HomeOptimizer. For simple situations like this, HomeOptimizer is not necessary. However, it requires diligent behavior on the part of the homeowner to ensure that the EV only charges during the super-off peak hours of midnight and 6 am, and that any delivery of battery energy to the grid happens only between 4 pm and 8 pm (the peak hours). Both features were customized by the homeowner with the help of ModBESS.
The figure above illustrates the net consumption and production for the house during June 20th, 2022. The period from midnight to 6 am (super off-peak) electricity. There was some spillover on that day, extending for one hour into the off-peak hour of 7 am. For the next four hours, even though the sun was shining, the solar energy was used to charge the battery. From 11 am until 3 pm, the solar energy was sent back to the grid. Most significantly, however, for the hours of 4 pm and 5 pm the entire energy from the battery was delivered back to the utility, and the homeowner received compensation for energy produced during peak hours (about $3.00 for this day). For the hours of 6 pm and 7 pm the battery was depleted but there was little peak energy consumption on that day. For the hours of 8 pm to 11 pm (off-peak) the consumption was also small.
The next figure illustrates electricity consumption for same entire week in June.
The next figure illustrates the costs to the consumer during the May/June period, broken down in detail. (This consumer is signed up for the Clean Energy Alliance Community Choice Aggregation program who provided these numbers):
In conclusion, choosing the right rate structure, the right battery size and the right operation schedule can result in significant benefits for a homeowner and for the utility. In addition to its role as the provider of battery and load control software for homeowners and business, ModBESS can also act as a consultant in the rate selection, battery, solar sizing and the creation of fixed optimal operating schedules for smaller homes and applications.
