Solar Inverter Sizing
choose the right solar inverter size
for your solar power system.
Solar inverters convert the low voltage DC electricity created by your solar panels to the 120
volts AC electricity used by household appliances.
Sizing a solar inverter is an important part of
any solar installation, big or small. Since your solar energy system is going to be
producing and sending DC electricity to your inverter, you're going to need to have an
inverter size that can handle the load and convert it to AC power. This requires knowing how
to size an inverter properly.
How To Size
If you're going to understand how to size an inverter you must first understand how
inverters are rated.
How Inverters Are Rated
The first way inverters are rated is in Watts (or Continuous Watts).
1. Continuous watts is the total amount of watts the inverter can
support indefinitely. A 2000 watt inverter can power up to 2000 watts continuously. A bigger
inverter size could handle more.
For your inverter to be right for your system, it's watts rating must be approximately
equal to your solar system's watts rating. This is the correct way to size an inverter.
Therefore, if your solar system is rated at 2000 watts, you'll need a solar inverter
with about 2000 watts, maybe a little bit more. But not too much more or the efficiency
will drop. You can learn
more about watts by clicking here to go to the Electrical Fundamentals section of our
If you want to run multiple appliances at the same time and want to make sure your
inverter can handle the load, just add up all the Continuous Watt ratings of all the appliances
that may be running simultaneously.
Depending on the total continuous watts you get, you can determine if you're inverter
can handle it. This is also an important part of inverter sizing (how to size
So if the total continuous watts of all the appliances that may run at the same time
is 3000, it's too much, you'll have to run less appliances at the same time.
The second way solar inverters are rated is in Surge Watts.
Surge watts is the amount of power the inverter can support for a very short
time, usually momentary. A 2000 watt inverter rated at 4000 surge watts can handle up to 4000 watts
momentarily while starting things like motors - which usually require more power than normal to get
For your inverter to be right for your system, it's surge watts rating must be
approximately equal to (or greater than) the potential surge watts of each appliance.
You can find this out by looking at the sticker on the back of all of the appliances
you will be using with your solar system and checking the potential surge watts of each
appliance. By doing this you can determine the minimum surge wattage you'll need your inverter
to be rated for. Usually, you'll need about 1.5 to 2 times as much surge watts as continuous
watts for a good measure of surge protection (more, if powering heavy duty equipment).
Therefore, if the highest surge watt rating on any of the appliances you plan to use
with your solar system is 4000, you'll need a solar inverter with a little over 4000 surge
Input Voltage - Should I get a 12v 24v or 48v
The next rating you have to look at when sizing an inverter is the input voltage.
For correct solar system sizing... your solar panels, inverter and battery bank all
need to use the same voltage.
So the input voltage of your inverter will depend on the inverter's power or watt
rating. For inverters with a relatively small amount of power like 100 watts, the voltage will
be 12V, 24V and 48V. For higher powered inverters, the input voltage will likely be more.
You can learn more about volts
by clicking here to go to the Electrical Fundamentals section of our website.
Length of Wire & Solar
One of the factors that can affect your inverter's
performance is the distance between your solar panel array and your battery
bank. The longer the wire used here, the lower your inverter's voltage should be to
perform optimally, because with long wires voltage drops and current increases.
The higher the voltage and the lower the current, the shorter length wires you can
use. With longer wires, you would need to use thicker wires. This is covered in the Solar Wire Types
Inverter Stacking (Using Multiple
Sometimes people connect more than one inverter together to "stack" up more power. This
would typically be done if you have many smaller inverters and want to join them together to form a
If your inverter demands increase in time (because you added more solar panels) you can either
buy a bigger solar inverter or wire multiple inverters together.
When you install and wire two inverters together, it's called inverter stacking and it can
provide either more power or higher voltage.
If two compatible inverters are wired together in series, you can double the output
voltage. This inverter stacking technique would be used if you
only had two smaller inverters and had to provide 120/240 volts AC.
However, if you were to wire them in parallel, you would double your power (watts). This solar
inverter stacking technique would be used if you had two smaller inverters but also had a solar
system that was rated at much higher watts (power) than what a single inverter could handle. If you
wired two 2000 watt inverters together in parallel, they would be able to handle 4000 watts (4KW)
Inverter Performance With Less
By correctly matching your solar panel's,
your battery bank's and your inverter's rated capacities, you can improve the performance of
grid-connected solar systems.
However, when the sun is not at it's brightest and the system isn't producing at close
to full capacity the inverter will be operating at partial load and it's efficiency will
Energy loss also occurs when an inverter is too small to operate in conditions
of overload. Another important thing to consider in pv inverter sizing.
An average quality Modified Sine Wave solar inverter can cost
anywhere from $400 - $1000. These low to medium quality range inverters can operate with small
to medium sized systems and relatively speaking provide good performance, reliability and
Obviously, unlike more expensive inverters (True Sine Wave inverters)there is
typically a moderate amount of energy or performance loss, but not if your appliances aren't too
high tech and your solar application isn't too demanding.
If you want to get a good quality inverter for a pretty big system, it would probably
cost you about $900 to $1500 for a 2000 to 3000 watt Modified Sine Wave solar power
If you want to be able to run basically anything plus have all the automatic
features, you would likely have to pay about an extra $500-$1000 for a True Sine Wave
solar power inverter.
These higher quality Sine Wave inverters are computer compatible and computer controlled which
will add automation and true convenience to monitoring and protecting your solar power system.
Never forget to factor in convenience and practicality when doing your solar inverter sizing.
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