Skip the USB lunch box. Buy a HotLogic Mini.

Most built-in heating lunch boxes are only strong enough to keep food lukewarm, not heat it. The thing that actually works is a plug-in mini oven called the HotLogic Mini.

The problem is physics. The cute little lunch boxes with built-in heating use USB power — usually 5V at 2A, which is about 10 watts. You need 50 watts or more to actually heat a cold meal from the fridge. So these models don’t cook or reheat anything. They just sort of take the chill off the top layer, and your rice stays sad.

The HotLogic Mini is the opposite. It’s basically a small insulated bag with a heating plate in the bottom. It plugs into a normal wall outlet (or your car’s 12V port), draws around 50 watts, and gets hot enough to bring fridge-cold food to a safe, steaming 165°F in about an hour. You put in your own microwave-safe container, then the whole bag warms your lunch. It’s not a lunch box with a container built in, but that’s sort of the point — it reliably works, and you clean the container like normal.

If you insist on an all-in-one electric lunch box, get one that plugs into the wall rather than USB. Some exist, and they work better, but reviews are mixed on durability. If you have access to a microwave at work, that’s still the easiest route.

Your lunch deserves better than lukewarm.