There are charts and tables here you can use for guidance. You may skip to those if you want, but it is important that you learn how to calculate appliances wattage consumption. Homes and RVs use appliances in different ways so you have to figure out your total power usage. To find your. Now you have to calculate how many hours per day an appliance runs. A 100W stereo running for 2 hours day uses 200W (100W x 2 hours = 200W). A. Make sure you include peak / surge watts in your calculations. A fridge may only use 700W running, but it needs those 2000W to get started. Include that wattage. As we stated earlier, 20-30 solar panels can produce 900-1000kwh per month, the average power consumption of an American home. But the number you need. In a word, yes, you need a battery. The more appliances you use, the more batteries you will need. Your usage determines how many will be required. Let's start.