Powerchairs
Warning:
You will see many advertisements in the press but bear in mind that most of these companies are national and employ "local" 
salesmen. To finance the adverts and salesmen, prices can sometimes be increased. Caution should be observed. A commission-based salesman who has travelled many miles can often be very keen to obtain a result. A company who will not send out leaflets first, complete with a price list, should be regarded with suspicion.
There are four main types of powered, or electric, wheelchair. Indoor, Indoor/Outdoor, Outdoor/Indoor & Outdoor.
Indoor
Before buying an indoor chair you should check to see if you meet your Health Authority's criteria for free supply. Most people requiring an indoor chair do qualify and receive not only the chair free, but all it's subsequent maintenance free. These chairs are ideal for around the house but not outside. Health Authority-issued powerchairs are not ideal for outdoor journeys or use in gardens unless on smooth surfaces as the castor wheels (the small wheels) tend to be tiny
Cost around £1500
Indoor/Outdoor
As the description suggests theses chairs are still small enough to be used indoors but have a reasonable outdoor capability including, in some cases, kerb climbing. Some are reasonably car portable. The difference between this type and outdoor/indoor is the size of the chair and castor wheels. Larger castor wheels whilst being great outside can tend to drag on carpets and cause damage.
Cost from £1800
Outdoor/Indoor
These chairs retain some ability to be used indoors but this is subject to the type of flooring and dimensions of doorways. The larger castors and batteries give better performance and ride. Most chairs will be able to cope with rough ground, grass & even woodland paths. The down side is that car portability can be a problem but this need not always be the case.
Cost From £3600
Outdoor
These are large chairs usually with large wheels and are often front wheel drive. Large batteries can take these chairs up to 25 miles. Their sheer size makes indoor use virtually impossible in a normal home.
Cost from £3500