Monday, June 22, 2009


Many of you may have just enough exposure to electricity to maybe confuse you or to even frighten you. With this in mind, I am hoping the below information may be of some value to you who may have questions about what electricity is. I will make electrical comparisons to that of water to help you have a better understanding since most of you are familiar with water. I will not attempt to be technical. Keep in mind, that this is just an brief overview and for a better understanding of electricity you will need to acquire and read additional resources.


You may find the following helpful in converting the value of these terms into another value...

AMPS = Watts / Volts
VOLTS = Watts / Amps
WATTS = Amps x Volts
Kw = 1,000 Watts


ELECTRICITY is an electromotive force (voltage) and the flow of electrons (current) through a conductor (wire). Think of electric as water flowing through a pipe. The pressure of the water would be represented by voltage and the rate of its flow would be its current (amps). So for example, a flow of 12 pounds per square inch of water at the rate of 4 gallons per minute is similar to 12 volts (pressure) as 4 amperes (current). To increase the flow of water you need to increase the size of the pipe, with electricity you would increase the wire size, which decreasing the wire resistance allowing an increase of current. This flow is called AMPERAGE in electric or you apply more pressure to the water, in electric this pressure is called VOLTAGE.

There are two types of electricity: ALTERNATING CURRENT (AC) which you will find in your home and DIRECT CURRENT (DC) which you would find in say your flashlight or automobile. In AC the flow of electrons first flows in one direction and then they reverse and flow in the other direction. While DC the flow of electrons is in one direction from minus (-) to plus (+).

Here are the major parts which make up electricity...

Voltage (E)

Measured in VOLTS, indicates the electrical "pressure" in a system. So if you were to take the pressure at the base of two water tanks of the same diameter, one being 120 gallons and the second being 240 gallons, you would see that the larger of these two tanks has more pressure. This is the same with 120 volts compared with 240 volts. The symbol for volts is V.

Current (I)

Measured in AMPERES (AMPS), is the quantity of electricity (electrons) that is flowing in a circuit. One amp is equal to the movement of one coulomb per second or 6,280,000,000,000,000,000 electrons per second. Again using water as our example, a pipe 4 inches in diameter will supply a larger amount of water than a pipe 1 inch in diameter. This is important to remember as the size of the wires used in an electrical system will determine how much electric current can go a distance from point A to point B.
The symbol for amps is A and the amount of amps used in an hour is amp hours (AH).

Resistance (R)

Measured in OHMS, is the resistance to the flow of electricity. It is a property of all electrical devices and is present in all of our wiring. The word impedance is often used instead of resistance. Impedance is a complex form of AC resistance that can can change with frequency. For a DC system and for this short lesson we will only be using resistance. The symbol for ohms is Ω.

Power (W)

Measured in WATTS, indicates the rate at which electrical energy is being used. The symbol for watts is W.


Measured in (for our purposes) WATT HOURS (Whr) or KILOWATT HOURS (kWh). This is the amount of electric used in the time period of one hour. For example a 25 watt light bulb in service for one hour uses 25 watt hours of electrical energy. If that same bulb was left on for 100 hours your total energy usage would be 2500 Whr or 2.5 kWh. Don't confuse energy with power. Power is the rate at which energy is being used.

Ohm's Law
This is the relationship between VOLTS, AMPS, and OHMS. This law can be explained by the chart below.

Don't let this chart scare you, it is really quite simple to work with. It graphically shows us the relationship between VOLTS, AMPERES, OHMS, and WATTS. This chart is a powerful tool because you can refer to it to change value from watts to amperes as you size your PV power systems. You can also use it to determine the size wire is needed to minimize resistance.

Current (I) is equal to E/R or A=V/Ω
Current (I) is equal to W/E or A=W/V
Current (I) is equal to √of W/R or A=√W/Ω

Ohms (Ω) is equal to E/I or Ω=V/A
Ohms (Ω) is equal to E/W or Ω=V/W
Ohms (Ω) is equal to W/I or Ω=W/A

Voltage (E) is equal to IR or V=AxΩ
Voltage (E) is equal to W/I or V=W/A
Voltage (E) is equal to √WR or V=√WxΩ

Power (W) is equal to EI or W=VxA
Power (W) is equal to IR or W=AxΩ
Power (W) is equal to E/R or W=V/Ω
Like I said, this is just the basics, for more detailed information you will need to do an Internet search.

Terry R. Wolff

Saturday, June 20, 2009


Hi I am the co-owner of Solar Taos, LLC and run an on-line Solar Product Catalog. Due to all the calls I have fielded over the years about basic solar energy questions and issues, I have started this blog.

It will take sometime to get to all the questions I have been asked but eventually I hope to have this blog as a solar resource where you will be able to come and view the topics which interest you.

Here are some of the topics which I will be covering....
  • Basic electricity
  • Solar, wind, and small hydro electric production
  • Utility free electric production
  • Solar electric production tied to your utility
  • Solar electric products
  • Solar heating products
  • System design and maintenance
  • Solar batteries and their maintenance
  • And other topics
Here is where you can find some basic terms used with solar electric and with solar air and water heating and information on battery maintenance. I will do one post in the future that will include some important resources to help you.

If you have a question, you can email it to me and I will post it as a new topic.

Should you be interested in knowing more about me, go to

Terry R. Wolff