Electricity in a camper van is extremely useful (and to be fair, outside of a camper van as well). In my van, I use is to power the lights, diesel heater, water pump, wifi access point, sound system, microwave, kettle, and the roof vent (and even all at once, if for whatever reason I ever find the need to).
The internet is full of a lot of valuable blog posts about people’s various takes on designing their battery and solar systems, each having a different set of priorities and constraints. For me, being able to power all of the above without having to be extra conservative with energy usage as well as being able to leverage solar energy were the key requirements. Additionally, I wanted to be able to monitor the system remotely. The setup I ended with is a 5kWh custom LiFePo4 battery pack, monitored and charged using an ElectoDacus SBMS40, and an array of 600W of solar panels.