A horsepower rating between 2 1/4 and 3 1/4 is optimal for routers. They will also usually be between 12 and 15 amps, electrically speaking. They work with any standard electrical outlet and have a very consistent power delivery because of this. You won't find portable routers with a battery that perform as well as ones that plug into an outlet. They just aren't as powerful.
2. Minimum/Maximum RPM Speed
Being able to change RPM speeds is very important in a router. Certain projects call for specific RPM speeds, and if your router isn't able to adhere to the speed requirement, you won't be able to complete the project. That's where a variable speed router comes in handy. Usually, from 8,000-30,000 RPM is sufficient to cover the RPM spectrum of most jobs out there. Look for routers that fall within this RPM range.
3. Variable Speed Dial
A variable speed dial allows you to make the most of controlling the RPM. There are usually preset speed settings that allow you to zero in on a specific RPM with the push of a button. Look for this functionality in the routers you consider.
4. Fine Depth Adjustments
Being able to adjust the depth of the bit is crucial to completing projects in the field. If your router doesn't have bit depth adjustment, look to another model entirely. Almost always, every project will require a different specific depth.
5. Aluminum Construction
If you want to make sure your router is going to last for years without damage, look for all aluminum construction. Aluminum is very good at holding up well against abuse and can extend the life of your router for more years than you might think. The outer shell, at the least, should be made of high quality aluminum.
6. Sealed Interior
With any router, pieces of sawdust and other debris can get lodged in the inside of the motor if the router isn't sealed properly. So to ensure your router is going to last for many years, make sure that the insides are sealed off, away from any possible fragments of material you're cutting.
7. Soft Start Feature
In order to extend the life of the engine, a soft start feature is great to have. Soft start routers come with speed control, which allows it to gradually work up to full operating speed. This is easier on the engine and extends its life. You have no idea how hard it is on a motor to just be switched on to full speed right away. It can take years off the life of an engine, hard starting all the time.
8. Warranty, Manufacturer, And Amazon Review Score
The router you're considering should have at least a 1 year warranty to keep you safe from factory defects. Also, the manufacturer of your router has a lot to do with how long it's going to last you. Some good manufacturers of routers these days are Bosch, Porter-Cable, Triton, Black and Decker, Hitachi, and DeWalt.