This proposed design for Iceland's electricity transmission pylons came from American architect Choi + Shine, and shows giant, human-like structures
In the contest, run by the Royal Institute of British Architects (Riba) for the Department of Energy and Climate Change and National Grid, architects, designers and engineers are being urged to come up with new designs.
Ministers and industry say new pylons and infrastructure will be needed across the UK as the equivalent of 20 new power stations are linked to the network, including renewable sources such as wind. National Grid said it would give "serious consideration" to developing the winning design for use in future projects.
But the competition comes too late to affect the latest addition to Scotland's network of pylons, with those forming the forthcoming Beauly to Denny line retaining the familiar 1920s lattice design.
There are currently 88,000 electricity pylons in the UK, including about 800 of the biggest in Scotland.
The 50-metre high steel lattice towers in the transmission network carry electricity for thousands of miles around the country. Their design - by architect Sir Reginald Blomfield in 1927 - makes them resistant to high winds and lightning strikes and able to cope with the load and tension of the cables.
Nick Winser, National Grid's executive director UK, said: "Much of the new low-carbon generation is planned for remote or coastal areas, which means new infrastructure will be needed to get the electricity we need to our homes, businesses and vehicles.
"While underground connection will be a viable solution in some sensitive locations, new and replacement pylons will be needed, and National Grid is equally keen to support the development of the most visually acceptable overhead solutions."
He added: "The pylon as we know it has served the nation well, but new technologies and materials mean there may now be opportunities for new designs."
Other countries have experimented with designs for pylons, but Iceland last year rejected plans to sculpt pylons into human-like lattice figures. Another of the contenders, architectural firm Arphenotype, had proposed more curving, "organic" shapes to carry electricity.
Italy accepted futuristic designs resembling a plant stalk or tree splitting in two to hold power lines, while France built a similar set of pylons in the 1990s with two towers featuring curved tops.
For Scotland's 137-mile line of pylons between Beauly and Denny, however, is it too late for a design change.
The scheme, due to be completed by 2015, was approved by Scottish ministers after a lengthy battle with local opponents.
A spokeswoman from Scottish and Southern Energy, which is behind the project, said: "The towers we are using have been designed for that line."
The Riba competition closes on 12 July, and shortlisted entrants will be given the chance to work with National Grid before final designs are submitted in September. Judges will then name the winner in October.