Low Frequency Inverters and Inverter-Chargers
Low frequency inverters build their AC output through a large line-frequency transformer. It adds weight, and it’s a design with decades of field history behind it. Our low frequency lineup is Victron: MultiPlus, MultiPlus-II, Quattro, and Phoenix, from 800VA mobile units up to 15kVA.
Low or high frequency isn’t a quality ranking, so judge each inverter by its surge rating and your loads. The comparison and our surge test below show why.
Low Frequency vs High Frequency Inverters
How it works
Builds a low voltage AC wave and steps it up through a large 50/60Hz transformer
Boosts battery voltage to high voltage DC, then switches it into AC at high speed
Weight
Heavy. The Victron MultiPlus-II in our surge test weighed 71 lb
Light. The MidNite Little Rosie RE in the same test weighed 15 lb
Surge
Long track record with motor loads, varies by model
Varies widely by design, and the best hold up very well
Idle draw
Usually higher, since the transformer draws power whenever the inverter is on
Usually lower
Common uses
RV, marine, and Victron-based systems built around an inverter-charger
All-in-one hybrid inverters with built-in solar charging, plus compact off-grid units
Examples we carry
Victron MultiPlus, MultiPlus-II, Quattro, and Phoenix
EG4, Sol-Ark, Fortress Power, MNP, and MidNite Rosie and Little Rosie
1. Start with your surge loads
List anything with a motor or compressor: well pumps, air conditioners, refrigerators, shop tools. Compare each inverter’s rated surge in watts and how many seconds it holds it, not just the continuous rating.
2. Count the idle draw
An off-grid inverter runs around the clock, and it draws power even when nothing is on. A few extra watts adds up over a winter, so compare no-load consumption on the spec sheet.
3. Match the voltage and features
Need 120/240V? Many high frequency all-in-ones output split phase from one unit, while 120V Victron units are usually paired or used with an autotransformer. All-in-ones also include MPPT solar charging, while a Victron system adds a separate SmartSolar controller. Want a second set of eyes on your load list? Contact our support team and we’ll help you size it.
Watch: Low Frequency vs High Frequency Surge Test
Dexter puts a 71 lb Victron MultiPlus-II 48V 5kVA and a 15 lb MidNite Little Rosie RE through bounce house blower starts and a heater load, measures voltage and current on a scope, then compares both against grid power. The result wasn’t what we expected.
Surge Capacity Test: Low Frequency Victron vs High Frequency MidNite
Low Frequency Inverter FAQ
They have a long track record with motor loads, but it depends on the specific inverter. Compare rated surge in watts and seconds against your motor’s starting current. In our surge test, a high frequency MidNite Little Rosie RE held its voltage better than a low frequency Victron MultiPlus-II. Contact our support team and we’ll help you size it.
The copper and iron transformer that sets the output voltage accounts for most of the weight. It’s why these units are wall or floor mounted, and why the 5kVA MultiPlus-II in our surge test weighed 71 lb.
Usually, yes. The transformer draws a small amount of power whenever the inverter is on, even with no load. Victron inverter-chargers have a search mode that cuts idle draw when nothing is running.
Yes. The MultiPlus, MultiPlus-II, and Quattro are built around a toroidal transformer, which is why they’re in this category.