How Does PV Work?
When some materials are exposed to sunlight, they release small amounts of
electricity. This is known as the photovoltaic effect. When describing solar
cells, the photovoltaic effect is the conversion of sun energy into
electricity by the cells.
This is how it works. Sunlight is composed of photons, or particles of solar
energy. These photons contain various amounts of energy corresponding to the
different wavelengths of the solar spectrum. When photons strike a PV cell,
the energy of the photon is transferred to an electron in an atom of the
cell, which is made of a semiconductor material.
With its newfound energy, the electron escapes from its normal position on
the atom and becomes part of the current in an electrical circuit. When this
happens, the electron creates a "hole." Special electrical properties of the
PV cell, specifically a built-in electric field, provide voltage that drives
the current through an external load, such as a light bulb, a hairdryer or a
television set.
Am I eligible for Net Metering?
In California, any residential or commercial electricity customer who
generates at least some of their electricity is potentially eligible for net
metering. The basic eligibility requirements are:
Your generating system must be powered by solar or wind energy, or some
combination of the two.
It must not exceed 1 Megawatt of peak power output
Net Metering and Time of Use tariffs
Customers on time of use tariffs can take advantage of Net Metering. In
these cases, excess production is credited at the average time of use rate.
For example, if you generate excess energy during the "peak" period, SDG&E
will credit you at the average peak rate.
How big should my photovoltaic system be?
There is no one right size for photovoltaic systems. Every site is different
and the needs of system owners vary, too. System size depends on several
factors, including how much electricity (in kilowatt-hours or kW-h) you
consume, the orientation of the system, the tilt of the system, available
space and capital.
The first step to determining the size of the photovoltaic system you'll
need, is to reduce consumption. Saving electricity is typically cheaper than
generating it. Further, the smaller your overall consumption, the smaller
and cheaper the system you'll need. The second rule in photovoltaic system
sizing is DON'T oversize the system. San Diego Gas & Electric will not
credit you for any excess electricity generated on an annual basis; in other
words, in any twelve month period, if you generate more than you need, the
excess electricity goes into the SDGE grid and you will receive no credit
(See the Net Metering Section for more details).
You should try to size your system equal to or less than your annual
consumption. An easy rule of thumb is to take your annual consumption (in
kWh) and divide that by 1300 kWh/yr. (1kW of photovoltaics will generate
about 1300 kWh per year). This will give you an estimated system size. For
example, the Smiths consume 6000 kWh per year. If we divide 6000 by 1300 we
get 4.6. This means the Smiths need about 4.6 kilowatts (kW) of
photovoltaics to completely offset their annual consumption. Always check
with a licensed installer or contractor to determine the actual optimal size
of your system.
How much electricity will my photovoltaic system
produce?
How much a photovoltaic system will produce depends on the orientation, tilt
and location of the system, and the amount of sunlight hitting the
photovoltaic modules. On average in San Diego 1 kW (DC) of PV will generate
1550 kWh per year.
What size should my photovoltaic system be
(Commercial)?
Under California's net metering law, eligible systems cannot be larger than
1 Megawatt of peak power output. However, your system should be sized so
that it does NOT produce more that you annual electricity needs.
Estimate your annual needs and size your system to produce this amount of
electricity, or less, over a twelve month period.
Excess generation by your system one month can be used to offset consumption
of electricity from SDG&E in another month.
DON'T OVERSIZE YOUR SYSTEM! SDG&E won't give you credit for anything over
100% of you annual consumption.
There is no minimum system size to be eligible for net metering.
Are photovoltaics cost-effective?
The cost-effectiveness of photovoltaics depends on the future price of
power, which is complicated to forecast. When you purchase a photovoltaic
system, you are effectively buying all or a portion of your power for, at
least, the next 20 years at a fixed cost. If average long-term electricity
rates are above that fixed cost, the investment was worth it. If the cost of
power is below the fixed cost, the investment may not have been financially
sound.
Business-owned photovoltaic systems are the most cost-effective applications
due to state rebate programs and federal tax incentives. As of this writing,
electricity from the utility costs $0.18 per kWh, which is predicted to rise
at 3 percent annually for the next 20 years, resulting in an average cost of
$0.23 per kWh. Thus, coupled with state rebates and the federal tax
incentive, business-owned photovoltaic systems can expect to generate
electricity for about $0.15 per kWh.
Governments and non-profits, on the other hand, cannot take advantage of the
federal tax incentive, making power generated will be about $0.21 per kWh.
Residential customers, whose federal tax incentive is capped at $2,000, can
expect to generate power at about $0.20 per kWh.
For more information on state rebate programs and tax incentives, please
visit the PV Financial Assistance page.
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The answer to this question was last updated May 2006.
How much do photovoltaic systems cost?
How much you pay for a photovoltaic system depends on many factors,
including system type and configuration, the difficulty of installation and
available incentives. To be clear, the costs mentioned here are the
installed cost. This means the final cost (before rebates) to the consumer
for the equipment and labor to install and connect a photovoltaic system.
The installed cost of a residential systems typically ranges from $8 to
$10/watt, while larger commercial and institutional systems typically cost
$6 to $9/watt. Generally speaking, the larger the system, the lower the
cost. In addition, the larger the number of systems, for example a new home
construction development of 200 homes, the lower the cost. Contact a local
contractor/installer to get price quotes.
Are there any financial incentives available to
reduce the cost of PV?
Yes, visit the SDREO's PV Financial Assistance page to find out more.
How efficient are photovoltaic modules?
Photovoltaic module efficiencies range from 5% for some thin-film
technologies up to 15% for single crystalline technologies. These
percentages refer to the conversion efficiency; that is, of all the light
that hits the photovoltaic module, the percentage that is converted directly
into electricity. Conversion efficiency is a critical issue when space is
limited. The more efficient the module, the less space is needed to build a
system that produces a desired amount of electricity.
Does San Diego Gas and Electric offer Net
Metering?
Yes. Under California law, all public and private utilities, including
irrigation districts and cooperatives, that operated prior to January 1,
1998, must offer net metering. New electric service providers, who began
selling electricity after January 1, 1998, may choose to offer net metering.
What are the benefits of Net Metering?
The benefits of Net Metering are:
You will get full retail rate for excess power
First, net metering allows you to get full retail value for the electricity
you produce. It does this by permitting you to put any excess electricity
you generate back into the electric grid and retrieve it later, free of
charge. Your excess electricity now offsets electricity you would otherwise
have to buy at full retail prices. Getting this high retail value for your
excess electricity makes owning your own generating system more
cost-effective.
You can only get the full retail value for electricity equal to 100% of your
total annual consumption.
If your home consumes 6,500 kilowatt-hours annually, you can only get the
full retail value for 6,500 kilowatt-hours produced by your photovoltaic or
wind system (i.e., you fully offset your consumption).
However, if you produce 7,000 kilowatt-hours, you will not receive any
credit for the excess 500 kilowatt-hours. That excess power is just fed back
into SDG&E's power grid to be used by others.
You can "store" power on the utility grid
Because you get credit for your excess power generation, there is no
immediate need for batteries to store energy for use in the evening when
your system is not generating power. However, there are instances when
batteries are helpful. In addition, you can size your system to more
accurately offset your annual electricity consumption.
The interconnection process is streamlined
Customers participating in Net Metering can use simplified interconnection
forms. This is particularly beneficial to businesses because it simplifies a
previously complex process.
No standby charges
Recent changes to the Net Metering law eliminated standby charges for
commercial customers. Previously, commercial customers generating a portion
of their own electricity had to pay SDG&E a fee for the ability to draw
power from the grid when their system was not operating.
How does Net Metering store my electricity?
Net metering allows you to use SDG&E's electric grid as a big battery. There
could be times when your PV system will be producing more electricity than
your home or business demands at that moment. Under net metering, during
these times, excess power is fed back onto SDG&E's grid to be used by others
and you can take this same amount of electricity back out of the electric
grid at a later time. Net metering permits you to "bank" your excess
electricity and then withdraw it from the grid free for your use later time.
For example, on a sunny summer day when no one is home, a PV system might
produce more electricity than needed at the time. However, at night when
your system is not producing at all you'd need to get power from SDG&E.
Let's say you put 10 kilowatt-hours (kWh) of excess electricity into the
electric grid during the day, net metering allows you to take 10 kWh off the
grid later and pay nothing for them (it's a trade).
How will I be billed under Net Metering?
How you're billed under net metering is different if you're a residential or
commercial customer.
Residential
Just as they do presently, San Diego Gas & Electric will continue to read
your meter monthly. However, with net metering, you will receive a monthly
statement (not a bill) that indicates the net amount of electricity you
consumed or the net amount generated and put into the electric grid that
month.
If you ran the meter backwards more than forwards, you would be a net
generator for that month.
If you took more electricity from the electric grid than you fed back, you
would be a net consumer.
On the anniversary of starting net metering, you will receive a bill for the
amount of net electricity consumed over the last twelve months.
If you were a net generator over the past year (i.e., produced more than
100% of your total annual consumption), SDG&E will NOT buy any net
generation.
If you were a net consumer in any given month, you have the option to pay
that amount immediately or waiting for your annual bill.
Please note:
If your power generating system produces enough electricity to fully offset
your annual consumption, you will pay a meter fee of about $62 per year
($0.17/day). This is not a special net-metering fee. The $.17/day is used to
offset cost associated with meter readers and bill preparation. All SDG&E
customers pay this fee. For non-net metered customers, this fee is worked
into the transmission and distribution rates.
Commercial
The only difference between residential and commercial is that commercial
customers must pay off their balance each month.
Will SDG&E Pay me for excess electricity
production?
SDG&E does not actually pay you for excess power, rather they are crediting
you for the power you put onto their grid. The ability to send power back to
the grid is called Net Metering. This concept is described in much greater
detail in our Net Metering section. Think of net metering as a debit
account. When your photovoltaic system is producing more power than your
home needs, the excess power flows onto SDG&E's power grid, turning your
meter backwards. This excess power is like a "power deposit" into your
electricity debit account. Later, when the sun is not shining, you make a
withdrawal of that power.
The bottom line is that SDG&E will never send you a check for excess power,
and any electricity that you generated in a twelve month period above what
you need will not be credited to your account (See How Big Should My PV
System Be?).
Can I use my current electric meter for Net
Metering?
Generally, yes. Most residential and small commercial customers have simple
meters that are already capable of turning in both directions
(bidirectional).
For larger commercial systems, SDG&E may want two meters for net metering,
one meter to measure all electricity flowing into your business and one
measuring the excess you are putting into the electric grid.
However, if SDG&E wants two, one-way (unidirectional) meters, by law they,
not you, must pay for them. You are only responsible for having a single,
bidirectional meter, the type most residential and small commercial
customers already have.
What are some of the common misconceptions about
Net Metering?
These are the most common misconceptions about Net Metering.
SDG&E will pay me full retail rates for any excess electricity generation
above 100% of my annual consumption.
Sorry: SDG&E is not required to purchase/credit you for any excess annual
generation (more that 100% of your annual consumption). However, if they are
willing to buy this "net" excess annual generation, they do not have to pay
you full retail prices for it. While the actual rate paid would be up to
SDG&E, it would likely be less than retail and closer to "wholesale" rates,
which are much lower.
I will have to spend hundreds of dollars on special meters, inspections or
fees to get my system hooked up to the electric grid.
No you won't: You are only responsible for having a simple, bidirectional
meter, the type you probably already have. If your generating system meets
national safety and performance standards, you cannot be charged for
additional tests, certification or fees.
The kilowatt-hours of electricity I might still need to buy from an SDG&E
will cost me more than before I became a Net Metered customer.
Wrong: SDG&E cannot charge you anything extra for being a net metered
customer and no charges can be imposed on the electricity you generate.
How do I sign up for Net Metering?
It's simple! As soon as you decide to install a photovoltaic or wind
generating system, call or email one of the following people to request net
metering:
Ken Parks
Kparks@semprautilities.com
(858) 636-5581
Teresa Davies
tdavies@semprautilities.com
(858) 650-618
The earlier you contact SDG&E, the sooner you can get your system approved
for connecting the power grid. To connect to SDG&E's grid, you have to fill
out an interconnection application and sign an interconnection agreement,
which outlines SDG&E's requirements for you to safely connect your
generating system to the their electric grid.
Application (PDF - 29k)
Interconnection agreement (PDF - 53k)
While you are required by SDG&E to sign an interconnection agreement, there
are several things SDG&E cannot require of you to be interconnected with the
grid:
They cannot require that you purchase or pay for any meters beyond a simple,
bidirectional meter that you probably already have.
They cannot impose any requirements, standards, or tests on your system, if
it meets existing national standards for grid-interconnected systems.
They cannot require you to purchase any additional insurance. Regardless of
whether or not your utility has a written agreement.
If you are interested in a free onsite solar evaluation of your home or business please call us or click here to schedule an appointment. Rebates are expected to decline. Act now and lock your rebate before it drops again.
We at 1-11 Solar Can Provide You With Client Referals Our clients love to talk about their grid tie systems and we will provide numbers you can call and speak directly with them.