Conserve Power cuts the end that you spend on attacks by half. It's the same as doubling your end recovery rate.
I've never had it, but the best tactic would be to either use it at the beginning of long fights or combined with powers such as Hasten.
Slotting it for end reduction only reduces the amount of end it takes to activate the power. I think the usual slotting is 3xRecharge.
I generally use it as a panic when I run out of end, unless someone's about to fire off RA or something like that...
I use it as one of my many buttons to push before starting a fight. It's currently still 6-slotted with Recharge Reduction as Prox hasn't respec'd post-ED. If you get Force of Nature in the Force Mastery epic that will take CPs place in AV fights.
i have a form of it with my peacebringer, this may sound silly but if u have an endurance inspiration use conserver power just before ur gonna do nova because then when u have just use ur endurance insp and ur off fighting again!
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I normally use it before an AV/Monster fight, or a rather hard looking boss fight. Before ED when it was 6 slotted with RecReds I didn't need stamina.
3 Recharges and that's all it needs.
best time to use it is during a fight when you are low on end, you can carry on fightinf and still recover end.
I don't see the point in using it at the start of a fight as you usually have a full bar of end to use
I use Conserve Energy prodominately on my En/En blaster, dont feel i need stamina. Iv got all my attacks slotted for at least one endred.
If you fire it at the start of a fight you wont leave full endurance. Best tactic is to press it when you get low, it'll recharge your end back up to full while you fight. Even post-Nova it's fantastic, pop a blue and you're away again blasting at full capacity. It's a gr8 power to use at low end because as it effectively halfs the end cost of every power, if you'r RIGHT on 0 end, you'll pretty much b able to fire two attacks instead of one each pulse of end.
Pre-ED you could have it back up by the time it takes your endurance bar to go from full to empty (with no endred slotted) after the effect expires, but now you're looking at a little longer, hence the slotting of endred in most used powers.
The slotting is indeed 3x recred.
If you'd like an in-game demo and ur on Union just gimme a buzz @Amazing Shnyet
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If you find yourself very low on End, pop a CAB, Conserve power and resume blasting. You'll find that the CAB will last for ages. 
It's great for after Nova. Nova will drain all of your remaining End and stop you recovering it for twenty seconds. Regardless of if you have used Conserve power before or not. (If you use Conserve Power before Nova, it only reduces the End cost of activating Nova, not the additional full End drain.)
Nova + CaB + Conserve Power = up and blasting straight away.
You need to use the CaB because Conserve Power actually requires End to activate.
I slot Conserve Power with three Recharge Reductions. (I also use Hasten though.)
Edit: Heh, heh, Shny beat me to it.
[ QUOTE ]
Nova + CaB + Conserve Power
[/ QUOTE ]
I tend to go for:
Conserve Power + Nova + CaB
As you've (usually) got lots of spare end pre-Nova, and if you fire CP up then it doesn't take a chunk out of the post-Nova CaB.
This power is a little gem. 3x slot it with recharges and dont look back. Even with the amount of end I use, with this baby on I can keep chopping to my hearts content. 
back in the day when i used my nrg/nrg blaster i used it pretty much all the time as a compliment to using hasten.
i 3slotted hasten wick gives it a acceptable recharge post ED and 4slotted Conserve Power (recharges on both ofc)
wich ment i could actually "perma" CP attack till my fingers hurt and popping CP when hasten goes off safes the whole fight..
For me that is.. :P
@EU Brimmy - Union and Exalted servers
back in the day when i used my nrg/nrg blaster i used it pretty much all the time as a compliment to using hasten.
i 3slotted hasten wich gives it a acceptable recharge post ED and 4slotted Conserve Power (recharges on both ofc)
wich ment i could actually "perma" CP attack till my fingers hurt and popping CP when hasten goes off safes the whole fight..
For me that is.. :P
@EU Brimmy - Union and Exalted servers
Finally got conserve power for my new Nerg/Nerg blapper I'm making.
Trouble is I have no idea what it does. It just sounds great that by pressing a button I somehow use less end.
So my question is really three questions.
1. What does it really do.
2. What's the best tactic when using it? Turn it on at the start of every fight or as a panic button when you run out of End in the middle of a fight.
3. How should you slot it? Does the end reduxtion affect what it does or only it's cost. (So far I've only got a recharge redux since the time it takes to come online after using it is messured in geological times.)