See Return to Ravnica FAQ: http://www.wizards.com/magic/magazine/article.aspx?x=mtg/faq/rtr
YES this works with Overload (alternate cost), just like it would with flashback, or miracle.
YES this works with Replicate (additional cost) but NOT in the way you would expect. Replicate, like Kicker, Buyback, and Entwine, is an additional cost added on top of the normal cost. This means that no matter how many times you Replicate a spell, Electromancer only shaves 
off the total cost. This seems meaningless at first glance, because it's only a discount of , but multiple Electromancers stack.
Say for example you control two Electromancers and cast Pyromatics, Replicating it once. The cost increase of Replicate is applied first, resulting in a cost of 
- you are not casting two spells for each, you are casting the one spell for . The Electromancer's ability kicks in afterwards, reducing it by (one for each Electromancer) meaning you pay ... (see all)
Posted By:
adrian.malacoda
(9/26/2012 11:48:30 PM)
It's official: Tim "The Toolman" Taylor is an Izzet.
Posted By:
Totema
(9/6/2012 8:05:04 PM)
I find this card underwhelming in the duel deck due to lack of synergy with replicate.
@Ferlord
Yes Replicate have no interaction with this card's ability and that's a fact. I guess you're the one smoking.
Posted By:
Ezuna
(9/23/2012 10:01:24 AM)
@ Ezuna
Do you mean that the deck doesn't have much Replicate stuff, or if this card doesn't go well with Replicate?
BECAUSE IF YOU MEANT THE LATTER, I dunno what you're smoking.
Posted By:
Ferlord
(9/9/2012 7:31:43 PM)
'Electromancer'? .....ok whatever.
I still think Science-mancer sounds better %_%
Posted By:
DarthParallax
(9/8/2012 10:24:09 AM)
If you get 2 Goblin Electromancers on the field.
Get Djinn Illuminatus on the field.
Does Seismic Spike destroy all lands?
Posted By:
Squeekems
(11/6/2012 8:43:55 AM)
enchant with Dual Casting and use that saved red mana to effectively cast two of a spell for the same cost, spread the burn around nicely, for example double Arc Trail for just two red mana, especially useful when paired with Wee Dragonauts equipped with a Leering Emblem
Posted By:
Rasher
(9/19/2012 9:09:32 PM)
Does this reduce any overload costs?
Posted By:
wpken
(9/23/2012 9:50:17 PM)
I guess it does since it's an alternative cost to cast you miracle spell .
Well i like this guy but in the red blue deck i own almost every spells cost just 1...
Posted By:
MojoVince
(9/25/2012 9:55:53 AM)