Question: how much power does one solar cell produce?
Answer: Using 4 hours of full sun, gives you this equation: 250 watts x 4 hours. That's 1 kWh (1,000 watts) in a day per 250-watt panel. If you multiply 1kWh per panel by 30 days in a month, you'll find that each 250 watt rated panel will produce about 30 kWh in an average month.