I've written long explanations many times before and there are quite a few of them on these forums...

Here's a quickly I did for someone recently... he asked how to select a power system for his plane.

Snip -

Actually it's quite simple...

To get 1:1 you want around 120-130+ watts per pound maximum ( burst ) power.

So if your plane is going to weight 15.2oz ( as projected by the manufacturer ) then take a figure OVER this and multiply by 130watts...

So let's say the plane will weight 20oz AUW just for safety....

1.25lbs x 130w = 162 w

So a 180 watt motor will do the trick.

Assume that you'll use an 11.1v LiPo pack...

180w / 11.1v = 16.3A

A 20A-25A ESC will work fine

Thust HP says that a 8x6 prop spinning @ 11000 RPM produces about .234 HP

1HP = 745w

.234 * 745w = 174w ( right in the ballpark! )

So we can use an 8x6 prop and spin it at 11000 RPM.

11,000 RPM / 11.1v = 990KV or approximately 1000KV

I'd use an 1100KV motor to add a bit more power.

Finally let's find the battery we'll need... we'll want to drive it only to a maximum of about 15c if it is rated for 20C.

16A will be our maximum draw

16A * 20/15 = 21A @ 20c

So a 1000mAh to 1200mAh 11.1v 3S pack would be the smallest you can use... I'd go with something around 1300mAh+ for safety. 1800mAh would give you the flight times you want but adds weight.

So there you have it.

1300mAh+ 3S 11.1v LiPo
8x6e prop
20-25A ESC with BEC
1100KV Motor rated up to 180-200watts burst for 15-30seconds. ( look for a 150w motor or so ).

Snip

Knowing how to choose a power system affects your battery selections.