Solar's Glossary of Terms

Solar Terms and Definitions

Baseline Rate
This is the lowest or base rate you pay for electricity. This is shown in blue in the Tiered Rate Structure below. The entire tiered rate structure is founded on this baseline amount.

The baseline amount of electricity varies by several factors. These factors are:

Summer vs. Winter (actual electric rates can also change by Summer vs. Winter)
The region you live in (coastal, inland, mountain, or desert as defined by SDG&E SCE, or PG&E)
If you are an all electric household versus customers who use both natural gas and electricity or propane and electricity.
Some customers utilize a time of use rate (TOU) as well as subsidized rates for medically impaired customers.
There is another complexity to this: usually twice a year you get a bill that straddles between summer and winter so your baseline and tiers change in the middle of the billing cycle.

Building Integrated PhotoVoltaic Systems (BIPV)
BIPV is a term that generically refers to a PhotoVoltaic (i.e. Solar Electric) system that has been integrated as part of the building itself rather than a system that has been "bolted onto" a building. Very often the solar electric system is used as a roof or sometimes as a wall of the building.

Carbon Emissions
Carbon based pollutants released into the atmosphere that are a result of burning fossil fuels like coal and oil. One of the primary emissions is carbon dioxide that is a "greenhouse" gas that is widely accepted to be causing global warming.

Electricity (AC and DC),
Type of Solar Photovoltaic (PV) cells generate DC (direct current) electricity and the Inverter changes it to AC (alternating current) electricity that your house can use or can be exported to the utilities electric grid (Grid-Intertie).

Electricity can be thought of as flowing like water. The amount of pressure is like the "voltage" and the amount of water flowing is like the "current".

If electricity flows through the wire in only one direction it is called DC or "direct current". Batteries provide DC current to things like your cell phone and MP3 player.

AC or "Alternating Current" is when the current flows through the wire in one direction and then reverses to flow in the other direction. The electricity from the outlets in your home are a prime example of AC electricity.

Full Retail Price
The full price that you would pay the utility company for electricity used.

Grid-Intertie / Utility Grid
The utility company provides electricity to homes and businesses through its power distribution "grid". The grid is all of the interconnections that distribute power to electric utility customers. A grid-intertie is simply a connection to the utility power distribution grid.

In remote locations without power a "standalone" solar electric system would need to be installed.

Incentives / Rebates
The state of California offers rebates to offset the cost of your new Photovoltaic System. These are typically in the "thousands of dollars" range and work out to be approximately 10% of your system cost. They can be a lump sum paid when your system is first started (EPBB) or paid out over 5 years as your system produces electricity (PBI).

Additionally, there is a federal tax credit of 30% of the system cost which helps you recover much more of your initial investment, much more quickly.


Inverter
The equipment in a Solar Photovoltaic (PV) or solar electric system that converts the electricity from the DC (direct current) output from the Solar Panels to AC (Alternating Current) that can be used by home lights and appliances or exported back to the utility company.


kWh (Kilowatt Hours)
Kilowatt Hours is a measure of amount of electricity used (electrical energy). It is the basic unit the utility company uses to measure the amount of electricity you use and are billed for.

Note: Kilowatts (kW) are a unit of power. And power over time is energy. So Kilowatts (power) over a period of time can be measured in kWh (energy).

Mounting or Racking System for Solar Electric
A mounting or racking system is typically an aluminum or steel structure that solar panels are mounted on. It provides a physical connection to mount the panels on.


Net Metering
Electricity can be thought of as flowing like water. Your electric meter measures how much electricity flows through it so the utility can bill you for the amount used. Now what do you think would happen if you could "push" electricity back to the utility company. You have probably already guessed that the meter would run backwards. That's what Net Metering is and that is what a solar PV system does when you produce more electricity than you are using.

This is important because PV systems produce electricity only when the sun shines on them and they produce the most in the middle of the day. This is a time when many people are not home and are not using much electricity. So your electric meter runs backwards in this case, and allows you to "bank" electricity with your utility company for use when you are home. It's like the utility company buys electricity from you during the day and you buy it back when you need it.

In other words you pay for the "Net" amount of electricity used and so it is called "Net Metering". The utility company is effectively buying back electricity from you at Full Retail Price during the day when you are often using the least amount of electricity and generating the most.

The amount of electricity is "netted" annually starting on the first day your system is interconnected to the utility grid (Grid-Intertie). In other words, the amount of electricity generated over one year is subtracted from the amount used over one year and you pay only for the "net" or remaining amount for that year.

Pay for only for the amount of electricity that you actually use minus the amount your new photovoltaic electricity system generates.


On-Site Evaluation
An On-Site evaluation needs to be done, because every installation location is different. If you want the most out of your solar electric system a site visit is absolutely necessary. There's no way to know details about your roofline and shading without a visit. Don't believe those who say they can do a thorough job without a site visit to determine location, orientation, and sizing of your system first.


Photovoltaic Solar Cells (PV Solar Cells)
Photovoltaic (PV) solar cells are semiconductor devices that are commonly made out of very pure silicon (Si) that when exposed to the sun generate electricity. They are often called "solar cells".


Semiconductors
are materials that have unusual properties. They are not conductors like metals and are not insulators like many minerals or plastics. They have very unusual electrical properties that are not like either of these and this allows them to convert energy from the sun to electricity.


Solar Electricity Generation Systems
Systems that generate electricity directly from naturally occurring solar energy that is falling on the earth's surface every day from normal sunlight. The most common method of converting sunlight to electricity is using Solar Photovoltaic (PV) cells.


Solar Panels
Solar panels are simply groups of Solar Photovoltaic (PV) cells that have been packaged into a more useable arrangement.
The panel protects the solar PV cells from the elements, like rain. It makes them physically more durable because they are protected on the top and bottom by other materials (glass, metal, plastics) and usually on the edges by metal frames. They also provide a solid method to secure them to their mountings.


Tiered Electric Rates
Utility companies sell electricity as varying rates depending on how much electricity you use. This is known as a "Tiered Rate" because you pay a different rate in each tier as shown below. As you use more electricity you are charged more per unit of electricity used. Your Baseline rate is the lowest rate charged; then as you use more electricity the rate charged by the utility increases as shown in chart below. The basic idea is this: the more electricity you use the more you are charged per unit of electricity. The basic unit of electricity you are charged for is the Kilowatt-Hour or kWh. The utility company is trying to get you to conserve by charging a lot more if you use a lot or waste a lot of electricity. Low energy users pay less per kWh than high energy users. The idea is: if you use a lot of electricity then you pay more for your share than if you were a lower consumption user.

Here in San Diego Gas & Electric (SDG&E) territory there are 4 tiers for the rates you are charged for electricity.

Tier 1 - The first tier is called "baseline".
Tier 2 - The next tier is 100% to 130% of the baseline amount.
Tier 3 - The next tier is 130% to 200% of the baseline amount.
Tier 4 - The next tier is 200% and up of the baseline amount.
The baseline is an amount of electricity measured in kilowatt-hours (kWh) and you are charged one rate for this electricity. Then when your usage goes over this "baseline" amount and up to 130% of it (Tier 2) you are charged a slightly higher rate. Then when your usage goes over 130% of this "baseline" amount (Tier 3) you are charged a significantly higher rate. And similarly for when you go over 200% of the "baseline" amount (Tier 4).

It is very important to note that the Tier 3 & 4 rates are substantially higher than the Tier 1 and 2 rates for PG&E customers. And a solar power generating PV system will "shave off" the electric bill starting from the higher rates billed in Tier 4 and Tier 3 first. And eventually "shave off" the bill down to Tier 2 and then to Tier 1 if enough energy is produced.

This is important; because with Net Metering your total or "net" electricity used is reduced. Which means the electricity that the PV system generated is taken from the top of your usage which in effect removes the most expensive electricity used first. This is a big advantage. Your most expensive electricity is removed from your bill first.

To help understand the tiered electric rates here is an example to illustrate it. Imagine if:

the first 10 gallons of gasoline you purchase cost $3 /gallon
then the next 3 gallons cost $3.50 /gallon
then the next 7 gallons cost $8 /gallon
and anything over 7 gallons cost $9 /gallon.
Wouldn't you rather try to not use the $9 /gallon and $8 / gallon gasoline first or get it another way? That's exactly what solar electricity does with your tiered electric rates. It removes the most expensive electricity first. So if you are trying to maximize your savings then you want to size your solar system so that it gets rid of (or "shaves off") the electricity that would be charged in the Tier 3 and Tier 4 rates. This will improve your payback period and rate of return.