Power calculations for solar power monitoring, and wind generator dump load sizing.

Some electrical engineering calculations are difficult, BUT some are not too hard. I will try to describe how to make these calculations, and I will try to explain so it is clear. First of all, we will work with a few terms, which I will explain by analogy to make it easy to follow.
FIRST; we have Voltage which is the amount of electromotive force applied. Before you run screaming into the woods, just think of it as pressure, and our equivalent will be water (as the electricity) with pressure head as the voltage. The more pressure (Voltage) the more water (Electricity) flows. In these calculations the symbol for Voltage or electromotive force is (E).
SECOND; we have current which is a measure of the amount of electricity flowing past a single point. The equivalent is the flow of water through a hose. Increase the pressure (Voltage) you get more current flow. Current flow is measured in Ampers, Amps for normal use, and the symbol is (I)
THIRD; We will look at instantanious power, measured in Watts, which is the amount of real work we can expect from the voltage pushing, and the amperage volume being pushed at any given time. Think of it as a bucket (a battery is an electronic bucket) where the water is pushed in, and begins to fill that same bucket.
FORTH; we have Resistance, measured in Ohms. The water equivalent is the size of the hose carrying the water (amperage) push by the Pressure (Voltage). Make the hose bigger, or raise the pressure, and you get more water flow.
FIFTH; Power measured in Watt Hours. As the name shows it is the amount of actual power stored over time. This is how full the bucket gets over time. It is the amount described in THIRD above, over time (how full is the power bucket) and is a measure of what is available to use. Most houses use so much power that their measurement is in KiloWatt Hours (1000 Watt hours).
Sixth, we have dissipation or component wattage (NOT to be confused with the Wattage above).This is the amount of power a single part can absorb before it will burn up. The best equivalent is a string holding up the bucket. When too much wattage (water filling the bucket) is present, the string burns in half, and the part fails.

We have a few equations now, that are small, so do NOT stab yourself with that pencil, LOL!

E=I*R Voltage (E) = Current (I) Amps * Resistance (ohms) So if you know two variables, you can calaulate the last one.

Then we have P = I*E where power (Watts) = Current (I) amps * Voltage (E)

One more useful equation is P= (I * I) *R or Power = Current Squared * Resistance which is best used for checking dissipation for dump load resistors. One word of caution here, dissipation of dump load resistors causes HIGH temperatures on the component (the string is tough, and burns in half slowly) so keep the cotton pickin paws off the goodies!