Customer Incentive Programs
How Solar + Batteries Work
This page provides some basics about how household batteries work.
What a household battery enrolled in an incentive program typically does
Sunny Day
On a sunny day, a household battery is typically charged by solar panels while providing energy to the home (self-supply). Any excess energy from the solar panels typically pushes (exports) to the grid.
Cloudy Day
On a cloudy day, a household battery is typically charged by solar panels while providing energy to the home (self-supply). Typically, there is not enough excess energy to push (export) to the grid.
Nighttime
At night, a household battery typically provides energy to the home (self-supply) with whatever energy is left in the battery. There is typically no excess energy to push (export) to the grid.
Panels power home and charge the battery.
Excess energy can feed into the grid.
Panels power home and charge the battery.
Not enough excess energy to feed into the grid. The household may also need to use some utility-supplied power.
The battery provides energy to the home, but once drained, the home may use some utility-supplied power.
No excess energy to feed into the grid. May also need to use utility power.
How a household battery enrolled in an incentive program typically charges throughout the day
The graphic below describes where the energy is coming from to power the home, how much energy the battery has, and how much energy the household is using during different periods of the day.
Morning
The household wakes up and begins to use energy which may require some utility-supplied power. The sun comes up and the solar panels begin providing energy to the home and charging the battery.
Midday
The household has left the home, so energy usage is low. As the sun peaks at midday, the solar panels charge the battery and any excess energy can push to the grid.
Evening
The household returns home and starts to use energy. As the sun sets the battery provides energy to the home for as long as it can. Energy usage of the home is high so some utility-supplied power could be needed.
Nighttime
The household turns in for the night. The sun has set, and the battery charge is low or zero. Some utility-supplied power may be needed for the household.
How a household battery in an incentive program typically works to provide a grid service
To provide a grid service a battery will typically discharge a specified amount of energy while also supplying energy to the home. This is referred to as a "grid service event."
How batteries typically respond during a grid service event in the evening
At the time of this example it is evening. The sun is setting, the solar panels are generating less energy, the battery is likely charged, and the household energy usage is high.
Before the grid service event
Start of the grid service event
After the grid service event
How a household battery typically works when there is a power outage
Batteries can be programmed in different ways! Please verify how your battery has been programmed with your contractor and ask them for instructions and/or a demonstration.
How a household battery could respond during a power outage:
The examples below happen on a sunny day with a utility power outage where the battery is typically charged by solar panels and is providing energy to the home but is not allowed to push (export) excess energy to the grid.
Example 1
The battery does not provide energy to the home until utility-supplied power is restored. The household experiences no power to the home.
Example 2
The battery provides energy to the entire home for as long as it can.
Example 3
The battery provides energy to key appliances in the household like the refrigerator for as long as it can, but it does not provide energy to other appliances such as the washing machine.
