Every part except the wheels uses power to function. Each chassis has a certain power capacity, which depends on the number of stars that the chassis has. For example, if your chassis has a power capacity of 10, you won't be able to install a Chainsaw that requires 11 power on it.

The only way to increase the power of your chassis is to fuse a Power Toolbox into it. Power Toolboxes can be found in Supply Boxes.