I think lighting needs to be looked at. A floodlight seems like the only way to light up a room in bright light but it will drain multiple 100% storage batteries very quickly. I like blacklisting atomic lights to use more candles and lamps but getting zones of bright light after I have a solar house has been annoying.
Poking through the code, vehicle lights look pretty straightforward:
They are defined in data/json/vehicleparts/lights.json.
They’re flagged with CIRCLE_LIGHT for exterior all directional lights like emergency red/blue lights or flood lights, AISLE_LIGHT for all directional interior lights like aisle lights, CONE_LIGHT for directional external lights like head lights. ENABLED_DRAINS_EPOWER means they drain electrical power when turned on.
Vehicle lights have a bonus that determines how much they illuminate: 8000 for floodlights and headlights, 500 for emergency lights, 30 for aisle lights.
You could easily create a heavy duty aisle light that illuminated a larger area. Start with a bonus of 100 and see what that gets you.
Someone posted on reddit that you can make a enslaved shocker zombie for a cheap/infinite light source.
Oh, really? 
Easiest method by far is to drop a friendly turret where you need light. Free and easy, even acts as a decoy against nasties. Only practical if you have a control laptop though.
Earlier game your best best is probably a flashlight modified with the storage battery or UPS mod and a charger. Flashlight hooked up to a car battery should last for ~3.5 days. A heavy duty flashlight with the same setup will last half as long, but gives substantially more light.