If it were me I would get a 2 cycle gas string trimmer that takes
attachments (Ryobi makes a good consumer gas trimmer). You buy the
motor head and string trimmer together as a set and then buy the steel
blade edger. You'll have plenty of power and not have to drag a cord
around. Home Depot has Ryobi, Homelite, and John Deer (which is OEMed
by Homelight). Lowes caries Troybuilt (which appears to be OEMed by
Ryobi) and Cub Caddet (which is probably OEMed by either Ryobi or
Homelight, don't know which). I've had a Ryobi for about 8 ~ 10 years
and used it about every other week during the mowing season (which is
about from mid March to mid November around here) and it has never let
me down. The "expand-it" attachments from all of the above named brands
are interchangeable (in fact I have a John Deer brush cutter I use on my
Ryobi).

The 18" Ryobi RY3002 will run you about $119 at HD and the edger
attachment is about $69.

John wrote:
I want to buy a lawn edger and I'm wondering if the electric models (about
$80) have plenty of power or would I be better off going gas as with some
other things. Having never used an edger before I'm not really even sure if
you NEED much power. Advice appreciated.

John