Yes, I'm aware that amps are measure of instantaneous current. Like I said, everything I know about solar is from my experience with RV solar systems. For example, it's common for someone to say that they used 25 amps if their 100 amp hour battery is drawn down by 25 amps.
Right, but what if someone has a 12V battery and someone else has a 24V battery. If they both use 25A for 1h, how much energy are they using?
12V * 25A * 1h = 300Wh
24V * 25A * 1h = 600Wh
If you use Ah, your energy consumption in Wh depends on voltage - it must be specified.
Power in = power out
12VDC * 100A = 1200W input
120VAC * 10A = 1200W output
(inefficiencies ignored)
Am I correct in that amps X volts = watts? Therefore, 20000 watts/120 volts = 166 amp hours would be used, correct?
Only if you have a 120V battery.
At 220 volts that would be 90 amps hours, right?
Only if you have a 220V battery.
I know there are losses due to inefficiencies in the inverter but in principal, what am I missing?
A fundamental understanding of Wh.
A Wh is 1W continuously expended over the course of 1h.
20000Wh/24h = 833W - you're burning an average of 833W all the time.
833W / 12V = 69A
833W / 120V = 6.9A
10X the voltage requires 10% the current for the same wattage, i.e., current and subsequently Ah is dependent on voltage.
Would it be 12 volts because that's what the inverter would draw?
I'm not sure how many folks are using 120 and 240V batteries. Expressing AC consumption in amp hours is nothing I've ever seen before. Let's carry that through. A 1200W array can only generate, 1200W/120V = 10A. 1.66h * 10A = 16.6Ah or 10% of what you need. You can't change voltage arbitrarily without changing the results accordingly.
In terms of recharging the battery for what was taken out, isn't that Time = Ah / Amps? Wouldn't a 1200 watt array produce 100 amps (1200/12v=100)?
Yes, but you keep changing voltages. First you use 120V, then you use 12V. When you change voltages, the amps change.
That's why Wh is a little easier - it's independent of volts since it's incorporated into the value.
Daily energy: 20kWh
Array: 4kW
20kWh/4kW = 5 hours.
Note how the units carry through. You get to skip Volts and Amps altogether.
I looked at multiple calculators and they all back that up but I'd like to understand how that is wrong. Here's an article confirming in principal the charge time;
Let's look at how to charge RV batteries with solar and maintain battery power for your RV in this article. Many of your issues can be resolved and a significant amount of money can be saved by installing solar on your RV.
www.solarenergyquestions.com
You're not understanding the basics, so you're getting the calculator inputs wrong - Wh is consistent across voltages because both V and Ah are in the calculation of Wh.
5A * 12V * 1h = 60Wh
5A * 120V * 1h = 600Wh (10X the energy for the same current due to 10X the voltage)
Back to your consumption:
20000Wh/120VAC = 167Ah
20000Wh/12V = 1667Ah
The two above items are equivalent. If you change voltage, the Amps/Ah has to change accordingly.
You don't get free energy simply by changing your voltage.