New guidelines for Iowa
home solar energy systems
I
nstalling a solar energy system on your home can help you take
advantage of the sun’s rays, support the environment and save
money over time.
Solar energy systems depend on the power grid,
so it’s important to consider how they interact.
When you want to install a solar energy system, one
key question is how large of a system you need.
We are piloting a new calculation to help customers select the size
of solar energy system that best meets their needs. Sizing systems
according to need helps us hold down costs for all customers. This
new calculation is part of a pilot program that took effect
May 4, 2017.
Time
Time
Alliant Energy is issuing a new sizing guideline
We are balancing two issues:
Right sized system – 14¢ per Kw.
1. The importance of developing solar
energy
in –Iowa.
Overbuilt
system
14¢ per Kw for energy used, and
3¢ per Kw for excess energy.
2. Our responsibility to secure reasonable energy prices for all Iowa
customers.
400 Kw = 14¢ (credit use)
The cost of electricity
504 Kw
sizing
We make and buy energy on behalf of our customers. The less we pay
for power, the less our customers pay. We can produce or purchase
renewable electricity on the market at a fraction of the cost of privately
produced power.
15¢
12¢
9¢
Alliant Energy cost to
produce or purchase/kWh*
3¢
0¢
Natural Gas
Wind
Overbuilt system – 14¢ per400Kw
for
energy
used, and
Kw = 14¢
(credit
use)
When you size your system72%
according
= 504 Kw to the guideline, all
104 Kw =for
14¢ (bank
for future use)energy.
3¢ per Kw
excess
of the power you
will be eligible for compensation
700 produce
Kw
196 Kw = 3¢ (paid as check)
28% = 196 Kw
use
at the premiumTotal
rate.
Private solar
premium rate
15.3¢**
6¢
Benefits of Right
my system
system
104 Kw =–14¢
(bank
future use)
Total use
sized
14¢
perforKw.
according to the guideline
15.3¢** (used immediately)
Within
guideline
15.3¢ (excess generation)
2.8¢
2.4¢
You can build as large a system as you want – we do not restrict the
size. You will receive either bill credits or payment for all output from
15.3¢ (used immediately)
your renewable energy system.
To support solar energy development in Iowa, we pay a premium for
15.3¢ (excess generation)
thanall of the power
private solar power. This is where our new sizing guideline comes in.
The question Larger
is whether
you produce will be eligible
guideline
for compensation at the premium rate,
or whether
of it will be
15¢
6¢***
(excesssome
generation
How the sizing guideline is calculated
Alliant Energy
cost attothe (lower) market above
compensated
rate.15.3¢**
the sizing
guideline)
(used immediately)
12¢
Private solar
produce
or
purchase/kWh*
The guideline is a new calculation that estimates the size of system
When your systemWithin
is larger than the guidelines,
then some of the
premium rate
9¢ usage.
15.3¢ (excess
generation)
guideline
your home needs. It is based on your specific energy
generation may be
compensated at the premium
rate and
some may be
15.3¢**
compensated
at
the
market
rate.
6¢ on the customer’s
We calculate a customer’s required system size based
Natural Gas
maximum need (also called “load” or “demand”). Maximum need is Wind
3¢
similar in concept to streaming data – it means the largest amount of
15.3¢ (used immediately)
2.8¢
2.4¢
0¢
electricity being used all at once.
15.3¢ (excess generation)
Market rate Larger than
guideline
Why maximum need is important
6¢*** (excess generation
above the sizing guideline)
Electricity cannot be stored; it must be used instantly. Our local power
Market rate
Maximum
need is the
maximum
amount of
energy used
at any one
time.
Time
Maximum need is lower if
energy is used at different times
Need
Need
grids must be robust enough to deliver electricity at the moment of
How large
I build my solar system?
maximum
usage should
by customers.
Time
Larger systems may produce more than a customer needs at their
moment of highest usage and have the potential to strain the
neighborhood’s power grid.
As of April, 2017, we have helped connect more than 2,200 customerowned solar energy systems to our local power grid in Iowa.
Next steps
We will evaluate and provide the pilot’s results to
the Iowa Utilities Board. The pilot will be available
for at least three years from its effective date. It may
be extended for up to two additional years. Iowa
customers on the pilot can remain for the life of the interconnected
equipment, up to 25 years.
Questions? Call 1-800-972-5325
or email [email protected].
*April 2017 market cost of energy
**15.3¢ is the average residential retail rate
including energy and transmission cost.
***6.33¢ is the current Cogeneration and Small
Power Production (CSPP) rate for”available
non-firm energy.” The actual rate will be the
CSSP rate in effect at the time of the payout
© 2017 Alliant Energy 5909363 5/17 JS