How much current will an
inverter draw from my
This depends on the equipment
connected to the inverter. There is a
simple method to calculate how much
power your inverter is using: For 12-volt
inverters, divide the connected load by
10; for 24-volt inverters, divide by 20.
How much does an inverter consume
with a 400 W load connected?
For a 12 V inverter such as a Mass Sine
12/1200, consumption will be 400/10 =
approx. 40 amps. For a 24 V inverter,
say a Mass 24/1500, the corresponding
figure is 400/20 = approx. 20 amps.
It is important to remember that this is
only an approximation: The actual
consumption will tend to be some 5 to
15 % less, depending on the load type.
How thick should my battery
Using the method described above,
calculate how much power your inverter
will be drawing at maximum capacity (120
amps in the case of a Mass Sine 12/1200,
for example). Then count 3 amps per
mm². In the above example this is 120
divided by 3 = 40 mm². The standard
cable thickness closest to that is 35 mm².
This rule applies to cables up to three
metres in length. If the inverter is further
away from the battery, choose the next
size up (50 mm² for instance).
Does an inverter need
a lot of ventilation?
An inverter needs very little ventilation -
two approx. 60 cm² ventilation openings
are usually enough. Larger inverters,
from 1500 W upwards, need twice that
size. Inverters used in high ambient
temperatures, and those expected to
be operating at full capacity for a long
period, require openings that are four
times as large.
Can an inverter be used in
parallel with the generator or
No, stand-alone inverters cannot function
in parallel with a generator or grid
connection. A Mastervolt Mass Combi
is the solution if you need more power
than is available from the grid connection
or the generator. These models can
compensate for the lack of grid or
generator power using the batteries.
A Masterswitch or Systemswitch needs
to be installed when grid or generator
power is connected to the onboard grid
simultaneously with an inverter. The
main function of the Masterswitch is the
automatic and safe switching between
grid, generator and inverter power.
What is no-load?
No-load is the amount of current used by
the inverter when no loads are switched
on, while the inverter is switched on
What is efficiency?
An inverter uses a small amount of
energy during the conversion process.
The difference between the input power
and the output power is expressed in
percentages. The efficiency of modern
inverters is more than 92 %. This means
that a maximum of 8 % of the power
consumption is used to convert battery
voltage to 230V/50Hz. A connected load
of 250 watt, for instance, requires less
than 270 watt to be supplied by the
Efficiency versus output power:
What are trapezoidal or
square wave inverters?
Square wave and trapezium inverters
are often available in DIY shops and
supermarkets at low prices. These
cheap inverters are not suitable for
all loads, however, and therefore
not safe to use. Modern inverters
generate a sine wave-shaped
output current similar to or even
better than that of the public grid
and perfectly suited to powering
sensitive equipment. Trapezoidal
inverters, also called modified sine
wave, are the ancestors of the
modern sine wave inverters. As
the name suggests, they generate
an output voltage in the shape of
a trapezium. This type of voltage
is inappropriate for sensitive
equipment. The square wave
inverter is the predecessor of the
trapezoidal inverter and represents
the first generation of inverters. It
is also very unsuitable for delicate
Trapezoidal or modified sine wave
input voltage 12/24 V