One of the best extra accessories that can be added to most Permobil power wheelchairs is the ability to tilt the seating, commonly known as "tilt in space".  The tilt in space function is ideal if you are not able to perform pressure relieving lifts, instead you can relieve pressure by tipping the wheelchair seat all the way back for a minute or two.  When you purchase your Permobil you can choose how far you want the seat the tip, I believe it can either have 45°, or 50° of tilt.  Since there is no difference in price, you are probably better off opting for 50° of tilt as this will give you the best pressure relief.

Tilting wheelchair 

Pressure maps from left to right:

Upright; 45 degree tilt; 45 degree tilt with recline. The tilt with recline gives the best pressure relief in this case.

Remember that everybody is different. Some people weigh a lot more than others. It also depends on what sort of cushion you are sitting on. So bear in mind that the pressure mapping illustration on this page may differ quite a bit from you. It just gives you an idea of how a tilting/reclining wheelchair can help you avoid pressure problems

Images courtesy of SCI pages