A gardener was killed when his hedge-cutting tool hit an overhead power line.
Western Power Distribution (WPD) has issued a warning following the man's death last year.
The power company, which is responsible for distributing electricity in the South West, wants people to be aware of hidden dangers which can kill.
Another incident saw a man injured when his six foot long window cleaning tool touched an overhead electricity cable.
WPD has urged people to take precautions before starting work outside as they can forget to look out for overhead power lines attached to poles and pylons, or cables and wires above their heads.
While the electrical hazards may be out of sight, hidden in bushes and trees or even mistaken for harmless telephone cables, they can still be lethal.
A WPD spokesperson said: "Working outside or doing DIY in the garden carries hidden dangers that can result in life-changing injury and even death.
"In one incident reported to WPD in 2020, a gardener was fatally injured when his strimmer made contact with an overhead power line, while hedge cutting."
The company said it gets called out to incidents in which members of the public have been hurt every year.
Eddie Cochrane, health and safety adviser at WPD, said: "It’s vital that people take notice of these hidden dangers because coming into contact with them can be fatal.
"If you’re using ladders, going up scaffolding or using tools to reach high places, when cleaning gutters or trimming high hedges, you need to be aware of what’s around you.
"Look out and look up for hidden dangers. Let’s get the job done safely."
People are urged to plan in advance and to contact WPD for advice, if they are working close to, or have any concerns about, electrical equipment.