I was in a car accident on Sunday. In my car there were two booster seats and a carseat. There were no kids in the carseats. The insurance company is saying that since there were no kids in the seats they don't need to be replaced. Is this true? Should I replace them just to be on the safe side even though the insurance company won't reimburse me?

Fight the insurance company. IIRC, it was a serious crash right? Even if there were no kids in the seat, there could be stress on them. And you're in CA, and there is a law in place saying they have to replace them. I'll go see if I can dig up a link about it.

I was wrong, the California law states "if the seat was in use".

The load forces on seats not in use is significantly less. Figure the rough estimate of those forces to be calculated this way:

speed X weight (of child & seat) = crash or load force

Example:
A 45lb child with 5lb for the seat in a 35mph crash
35 X 50 = 1750

An empty seat in a 35mph crash
35 x 5 = 175

I don't know how much the seats weigh. That is just an idea of how to get a rough calculation.

Just my 2-cents.

Oh and we were taught in the nationally standardized training that occupied seats and seatbelts need to be replaced.