Watts or Amps?

[Shasta1]

If I'm computing my power requirements in order to properly size my solar system, should I do it in watts or amps?

[edman87k5]

Watts, unless you have a gymnasium sized solar setup.

[brianb]

Originally Posted by Shasta1

If I'm computing my power requirements in order to properly size my solar system, should I do it in watts or amps?

I'm not expert but they are a bit interchangeable, I was taught this formula...

Watts = AMPs x Volts

And of course using a little high school math you can rearrange this formula as necessary. For example: 24 Watts = 2 Amps x 12 Volts. So in short Watt is the power used (or provided) at the rated voltage. Watts are normally used in calculating solar power requirements.

[prof_fate]

Think of it like a garden hose.

Amps is the size (diameter) of the hose
volts is the pressure
watts is the gallons that comes out.

more volts = more pressure. more amps needs a bigger hose (or wire).
with a bigger hose or more pressure you can (but don't have to) get more water (watts).

If you're filling a bucket and need 5 gallons of water with a firehose or a straw you still need 5 gallons, one just takes a lot longer.

So if you are trying to charge a battery you are filling it with watts (measured per hour, or watt-hour, or for a house killowatt hour ( thousand) kwh).

To run a 5 w bulb for an hour takes 5 watts. If you run it off a battery for 10 hours you used 50 watts of power, total. So to recharge the battery you need to put 5 watts back in.