Originally Posted by emilymci99
Thank you so much!
You are on the right track estimating and adding up all your AC power consumers. You want to think about the maximum concurrent
AC power draw. You don't have to add all the appliances together just the ones that might be running at the same time. And you definitely want some overhead, as some appliances (especially things with motors, compressors, etc) draw a lot more power than they are rated for for short periods of time.
I second the recommendation to spend some time over at Diysolarforum. Lots of info over there and a really easy to use search feature compared to most forums.
A couple things to be aware of:
1. In my opinion there is no reason to even consider modified sine wave these days, spend the money on pure sine wave.
2. Especially with cheaper and off brand 12v inverters, ratings are often pretty inflated. In my opinion these inverters are best avoided but if you do buy one make sure to de-rate it in your head.
3. There are 'low frequency' and 'high frequency' inverters, both have strengths and weaknesses. Low frequency is much better
at handling high surge loads, much more robust, and often a bit more expensive. Manufacturers rarely state low frequency, but if its big, heavy, bulky, with a high (~3x surge rating) and a built in charger it is probably a low frequency inverter. For your situation, LF probably makes the most sense.
4. 4-6000W sounds like you are in the right ballpark if you want to be able to run 1 maybe
2 appliances + the water heater (which I assume you won't be able to easily control) concurrently. What will your system (battery) voltage be? In my opinion 12V is not advisable at that power level.