The damage caused by lightning strikes in south west Wales was the worst in 20 years, says Western Power Distribution.
About 100 homes are still cut off after 12 hours of electrical storms over Ceredigion, Pembrokeshire, Carmarthenshire and the Swansea area.
At its height 1,600 properties were hit. The company expects all homes will be reconnected by 19:00 BST.
Scottish Power said heavy rain was a factor in the loss of power to hundreds of homes, mostly in Gwynedd.
A fallen tree and landslip also blocked the A465 Heads of the Valleys road between the Brynmawr and Gilwern roundabouts at 12.30 BST.
Western Power said at the worst point 1,600 homes were affected in Gorseinon and Gowerton in Swansea.
Another 420 homes were without power in pockets stretching from St Davids to Llanelli and the Pontrhydfendigaid area of Ceredigion.
Four flood warnings and nine alerts were still in place at 16:35 BST from Natural Resources Wales including tidal areas of Pembrokeshire, Carmarthenshire as well as the Wye estuary.
Arriva Trains Wales said services between Fishguard Harbour and Carmarthen were replaced by buses after signalling problems caused by lightning strikes.
A lightning strike had also caused signalling problems between Bangor and Holyhead.
It caused delays of up to 30 minutes for services between Llandudno Junction and Holyhead, which are now running normally.