A cordless planer will work wonders if you are going to need a tool to plane boards quickly and in locations far from a power outlet, but some planers are not strong enough to handle tough jobs. It is important to consider how you are most likely to use the cordless planer on a regular basis before going shopping for the model that will work best for you. If you will be using the planer often and for bigger jobs, even the highest quality cordless model may not be sufficient. For smaller jobs, however, or infrequent use, choose a planer that is well constructed and large enough for the job.
Most cordless planer models are rated by the battery size. 14.4 Volt batteries are common, as are 18 Volt models. There are larger and smaller models available as well. The higher voltage models will be more expensive because they will be better prepared to handle larger jobs, since the power output will be greater. Lower voltage models will be lightweight and appropriate for small, infrequent jobs, and they are likely to be far less expensive. Be sure to choose the cordless planer that is powerful enough for the jobs you will be doing.
More voltage does not necessarily mean more battery life. Be sure to read reviews of each cordless planer you are considering and take note of the effective battery life of the units. This will give you an idea of how often you will need to switch out batteries for recharging. Take note, too, of how often people find defective battery packs or a need for battery pack replacement. The time it takes to charge the battery to a full charge will also affect how useful the unit is for you during a woodworking project, so be sure to take note of the charge times of each unit.
The cordless planer you choose should also be lightweight enough to be handled comfortably and safely. The handles should be situated in such a way that control over the unit is improved during use, and the on/off switch should be easy to reach at all times. Many planers feature a security shut-off function; be sure to choose a model with this function to prevent accidents that can cause injury or damage to the wood. Take note of how easy it is to change out the planer blades, since they will need replacing periodically, depending on how often the unit is used.