Overkill??? Lighting HELP!!

I'm going to be setting up with a friend who is a semi-experienced grower, me less so, and I've got a couple of questions as to the neccesity of some aspects of his planned set up. My main questions are re lighting and how much is too much.

The plan is basically 10 plants in a 2mx2m tent, in oxy pots, decent in/out extraction, and 4 600w HPS. Is this going over the top with the amount of light? I should add that my friend is a semi-experienced grower but likes to throw a lot of cash at his grows, wheras I'd like to limit initial/ongoing costs as much as poss, so I was wondering if 2400 watt is way too much for the space and amount of plants?

He says the four lights are neccesary for even light distribution/canopy, but I'd like to know, for sake of set up cost/electric cost, whether 4 400w would do just as well? My thinking being, less heat=slightly smaller extractor required, also saving cash/electric. And also, after introducing plants to the main tent from the veg room, my friend uses 2 600 HPS to grow them up until he flips the light and adds the other 2 600's, am I correct in thinking it would be better to use 2 400w MH for this stage of veg because of the bluer spectrum=less stretch/shorter internodes?

I'm aware to a certain extent it's a case of the more light the better, I just don't want to be burning electric unneccasarily if I could yield the same using less. Has anyone got a link to a basic lumens/watt per square foot chart or something, as a guide to help me? I'd really appreciate more experienced growers input on this, for example, if you had a 2x2m tent, what would be your IDEAL set up to max yield? My friend pulls between 40-50oz from his set ups as described, so pretty good but is the same possible with slightly less light/power being burned?
Thanks in advance for for any help on the subject.

Your aiming for 50w per sq/ft so 6'x6' will be 1800w ,so you can drop off one 600 and go with 3.

Thanks for the quick reply. I said that to him but he maintained that having four lights gives a much better light distribution to get the even canopy. So, if 1800w is ideal, would 1600w from 4 400w be a better option or would the 200w less significantly affect yield?

50w psqft is minimum, anymore is extra bud any less is lacking

^Cheers, suppose I'm just going to have to bite the bullet and spend the extra $$$! Might try 2 400's and 2 600's, giving just a little more than the 1800/50psqm I need and see how that goes as opposed to the 4 600's. We,re actually planning on doing two 2x2m in the same place, hence the need to limit the electic usage as much as possible.

Any advice regarding the use of 2 400 MH instead of 2 600 HPS for late veg? Am i correct in thinking the MH is a better light spectrum for this growth stage, and this compensates for the lower amount of wattage?

Id use 4 to get an even distribution. How you going to distribute 3 in a square room that's a little bigger than 6ft x 6ft? If you can get the footprint of light that your reflectors give off and can get an array right id do 3 cause like buds said its 1800w divided by 36 is 50w a sq ft.

400s would be less than ideal as its a little under 50w a sq ft. And because the light penetration is less of a 600 and 1000

And you're right a metal halide is better for veg. But vegging can and is done by some experienced growers on here by an HPS. Granted every instance is because of having it laying around.

if electricty is your main concern and if you have the available power option run all your lights off of 240 volts this will cut your amp consumption in 1/2 overall costing less money for electricty i have a 1000w ballast that can use 120v or 240v at 120v its pulling 10amps on 240v it pulls 4.3 amps so when i got the first electric bill using just that one ballast raised my electric almst 40 bucks so i changed it over to 240v and its a little less that 20 bucks to run that ballast now

^&^^ Thanks for the replies

I think I'm going to try 2 400's and 2 600's, as from my limited experience I've found that even distribution is imperative, no matter the amount of lighting. Money isn't really the main issue, it's just that 2 2x2 tents blazing 2400w each plus hydro pumps, extractors etc is going to look highly irregular on my electric bill so I'm trying to limit it in as many ways as possible.

The domestic voltage is all 240v in my country anyway membrain, but cheers for the heads up mate.

Electric companies charge you for wattage use not amps used. A 220v will only give you the ability to run more on the circuit.. it won't lower your bill. That's why your bill is in kilowatt hours and not amps used.