Technical Bulletin
Table Of Contents
December 2020 1
Oversizing of SolarEdge Inverters, Technical Note
PV inverters are designed so that generated output power will not exceed the maximum AC power. In many cases,
oversizing the inverter, i.e. having more DC power than the inverter AC power, may increase power output in lower light
conditions, thus allowing the installation of a smaller inverter for a given DC array, or alternately, installation of more DC
power for a given inverter. However, too much oversizing of the inverter may have a negative impact on the total energy
produced and on the inverter lifetime. This document provides considerations for oversizing inverters and presents the
maximum allowed DC/AC oversizing of SolarEdge inverters.
Introduction
PV modules do not consistently perform at their nominal output rating. The module output power is affected by the
weather, the sun’s position during the day/different seasons, local site conditions and array orientation. In addition,
module output power may decrease due to aging, soiling and shade.
For an inverter with maximum AC power output (
,
) connected to a PV array with STC power (
()
), the inverter is
oversized if:
()
>
,
DC/AC oversizing is defined as the ratio between the array STC power and the inverter AC power:
/
(
%
)
=
()
,
∗ 100%
The maximum AC power output of the inverter (
,
) is the rated/nominal power of the inverter
1
.
DC/AC Oversizing Considerations
The main reason to oversize an inverter is to drive it to its full capacity more often. This will maximize power output in low
light conditions, thus allowing the installation of a smaller inverter for a given DC array (or alternately installation of more
DC power for a given inverter). Oversizing the inverter is typically not a requirement, however an experienced PV designer
may choose to oversize the inverter in order to maximize the power production, due to the following:
Actual PV module power vs. module nominal power
Financial considerations
On the other hand, too much oversizing may negatively affect the inverter power production: Inverters are designed to
generate output power up to a maximum AC power that cannot be exceeded, and they limit (clip) the power when the
actual produced DC power is higher than what the inverter can output. This results in loss of energy.
Oversizing the inverter also causes the inverter to operate at high power for longer periods, thus affecting its lifetime.
Operating at higher power also increases inverter heating and may heat its surroundings. Inverters will reduce their peak
power generation in case of overheating
2
.
Maximum Oversizing of SolarEdge Inverters
SolarEdge allows DC/AC oversizing of up to 155%
345
depending
on the inverter model according to below
specifications:
For Single Phase Inverters up to (and including) SE6000, DC/AC oversizing of up to 135% is allowed.
1
As specified in the inverter datasheet.
2
Refer to the inverter installation manual, (Inverter Power De-rating appendix) for details on how the temperature affects the inverter power
generation.
3
In all limits, the rated STC power of the modules should be used regardless of module location, tilt, or orientation.
4
When using SolarEdge's Designer, DC/AC oversizing is based on the maximum achieved DC power, given the site location and PV array tilt and
azimuth. This allows a connection of more modules in a string than possible using the STC specifications.
5
In Germany, utilities sometimes require to limit the AC power to 70% of the DC power according to EEG 2012. In these installations, oversizing of
155% is allowed.