Power Artifact
Enchantment — Aura
Enchant artifact
Enchanted artifact's activated abilities cost 
less to activate. This effect can't reduce the mana in that cost to less than one mana.
Douglas Shuler
Masters Edition IV (ME4)
• #57Rulings
Activated abilities contain a colon. They're generally written "[Cost]: [Effect]." Some keywords are activated abilities and will have colons in their reminder text.
(wotc • 2016-06-08)
Can't reduce Snow mana costs.
(wotc • 2006-07-15)
Only affects the generic mana part of activation costs. Colored parts of mana costs are not affected.
(wotc • 2004-10-04)
Can be placed on artifacts with no or zero activation costs, but this has no effect on them. It does not increase the cost to one.
(wotc • 2004-10-04)
Rulings
Activated abilities contain a colon. They're generally written "[Cost]: [Effect]." Some keywords are activated abilities and will have colons in their reminder text.
(wotc • 2016-06-08)
Can't reduce Snow mana costs.
(wotc • 2006-07-15)
Only affects the generic mana part of activation costs. Colored parts of mana costs are not affected.
(wotc • 2004-10-04)
Can be placed on artifacts with no or zero activation costs, but this has no effect on them. It does not increase the cost to one.
(wotc • 2004-10-04)