Tekkit Singleplayer: massive lag, Tekkit multi on localhost: no lag

[Digid]

So this is the situation:

When i'm running a server on my laptop, with me and a mate playing on it, everything runs fine.

However, as soon as I load the same level in singleplayer (copy paste it to the tekkit saves folder), I experience gamebreaking lag.

Is this because the SP mode takes more RAM to render the world than the Server needs?

Or is it because Tekkit isn't meant to be used in singleplayer?

Or is it something else?

Also, how do I fix it?

[SimpleGuy]

Or is it because Tekkit isn't meant to be used in singleplayer?

You answered your own question. That's why there is Technic.