How it works | General Info

A Crash Course in Electricity

Electricity is defined as "Electrons flowing in a line." They flow through some kind of conductor, generally wire. For the purpose of explanation, we will compare this to water flowing through a pipe.

The pressure of the water flowing through the pipe is measured in volts. The amount of water coming through the pipe is measured in amperes or amps. You can imagine that if we wanted to increase the flow through the pipe, we would need either a bigger pipe or we would need to push the water through at a faster rate. To push water faster you need more pressure. This is just like electricity: if you want to "push" more electrons through a certain size wire, you would have to increase the voltage.

The solar industry for the past twenty years has focused a lot on 12 volt systems. This was because of the great availability of 12 volt deep cycle batteries through the RV and transportation industries. Another factor was the availability of 12 volt appliances. This voltage is quite low for pushing a lot of electricity through a wire a long distance. The wire tends to be very large which is not only very expensive, but is bulky and harder to install.

These days 24 and even 48 volt battery banks and charge controllers are very common. Modern Grid-Tie systems typically have solar panels wired together in series to produce 'strings' that come out at 300 to even 1000 volts! This higher 'pressure' means that you can send more amps through smaller wire, getting the job done with less copper and easier installation.

Electrical power is measured in watts. VOLTS X AMPS = WATTS. To determine how much power is consumed by a given load (or appliance) we need to know how much time the load is on. A one-watt load that is powered for one hour is called a watt-hour. Utility companies work with so much electricity that they skip right to measuring your power by every 1,000 watts. This is called a kilowatt. When a kilowatt is consumed for one hour, this is called a kilowatt-hour.

If you look at your monthly electrical bill it will show exactly how many kilowatt hours you have used in the last month. If you add up the kilowatt hours (kwh) for the last year, then divide by 12, you will get your average kwh/month. This number is extremely helpful for sizing your grid-tie system.