Here is a link to a PDF copy of the 2015 Spark EV manual :
https://my.gm.com/content/dam/gmownercenter/gmna/dynamic/manuals/2015/chevrolet/spark_ev/2k15sparkev2ndPrint.pdf
Download it so that you can then easily search for things, such as "Programmable Charging Modes " (which starts on Page 5-21).
There are 3 types of Charge Mode Status:
Immediately: The vehicle starts charging as soon as it is connected to an electrical outlet.
Departure Time: The vehicle estimates the charging start time considering the programmed departure time for the current day of the week. Charging begins at the start time and is complete by the departure time only if sufficient time is allowed after the charge cord is plugged in.
Rate & Departure Time: The vehicle estimates the charging start time based on the utility rate schedule, utility rate preference, and the programmed departure time for the current day of the week. The vehicle will charge during the least expensive rate periods to achieve a full battery charge by the departure time. Electrical rate information from the utility company for the charging location is required for this mode. Also, if the selected electric rate settings result in a very long charge completion time, the vehicle will start charging immediately upon plug-in. For example, if the electric rate table is set up with all “Peak rates and the rate preference is to charge during “Off-Peak” rates only, then the vehicle will start charging immediately upon plug-in.
So, you need to :
1- set "Rate & Departure Time" (Page 5-22)
2- Edit Departure Time (set "departure time" to be 30 mins before your electric rates go up : 8am?) - (Page 5-22)
3- set your rates (Peak, Mid-Peak, and Off-Peak Rates) - you can just set Peak and Off-peak (10pm-8am) (Starts on 5-23)
4- Set your "Rate Preference Selection" to "Charge during Off-Peak Rates" (5-24)
(Note that if the vehicle won't fully charge between the "start" and "stop" times, it may start charging earlier. This shouldn't be a problem if you use 240V charging; if you use the 120V EVSE that came with the car, you will probably want to plug the vehicle in only after 10pm on those days that the "charge level" of the vehicle is less than 50%. You will have to see if the car starts charging immediately if you plug in the 120V EVSE when the battery is only at (say) 20%.)
(I think that the car will 'chirp' twice at you when you plug in if programmable charging is active.)
Another preference is "Priority Charging" - if this is enabled, the vehicle will ALWAYS charge up to 40% SoC (State of Charge) no matter what, and once 40% is reached it will "delay" charging until whatever you set.
Also, you can *always* override delayed charge (Page 9-36):
To temporarily override a delayed charge event, unplug the charge cord from the charge port and then plug it back in within five seconds. A single horn chirp will sound and charging will begin immediately.
To cancel a temporary override, unplug the charge cord, wait for 10 seconds, and then plug the charge cord back in. A double horn chirp will sound and charging will be delayed.
Also, the EVSE might consume power (pull electricity from the wall) even if not charging - for example, to cool or heat the battery. That is a good thing!