This is not a frequently asked question, actually, but, some basic knowledge of this can empower you to at least speak semi-intelligently about solar and how it works…It certainly would help “yours truly” to not have to listen to people misuse common electrical terms.
Basically, a Kilowatt is an instantaneous measure of power and it determines how “powerful” an electric system is. It is sort of like horsepower in a car. It determines what the instantaneous potential power is of the car. A kilowatt-hour (KWH) is basically how many kilowatts (KW) are produced and/or used in an hour, just like the car that can travel so many miles in an hour, it all depends on how much potential there is and how much the demand for that potential is.
A solar home system that is, say a 10 KW system, means that it has the maximum potential to produce 10 KW in a given moment. If the sun is out at its maximum angle for electrical production, it would be capable of producing 10 KW in one hour, hence the term 10 KWH. Most systems will lose 20% of that power converting from DC to Ac current (more shop talk but, helpful for wowing your guests) so, at maximum capacity the system might be capable of producing 8 kw of power in an hour. However, there is no “perfect” one hour of sunlight gain so, the wizards of computer and analytic science have pre-calculated average solar hour gains by region, throughout the US.
So, an average 10 KW system in Southern Florida is likely to be able to generate about 45 average kwh per day of electricity, based on around 5.8 solar hours of sun per day. The prototype solar home for JLH Sustainable, located in Naples Florida, for example, has a 6.8 kilowatt system and generates an average of about 29 kwh of power per day. This means the home is net neutral if the homeowner uses 900 kwh/month or less