Transformer and transformerless solar inverters
Every inverter turns the direct current from panels or a battery into the alternating current your home uses. The older way does it through a heavy transformer; the newer way does it electronically at high frequency. Each has its place.
Updated 27 September 2026
Two ways to make AC power
Panels and batteries produce direct current. Your fans, fridge and AC need alternating current. The inverter does the conversion, and there are two broad ways to build one.
A transformer-based inverter, also called low-frequency, passes the power through a large transformer of iron and copper to shape and step up the voltage. A transformerless inverter, also called high-frequency, does the same job with fast electronic switching and much smaller components.
How they differ
| Transformer-based | Transformerless | |
|---|---|---|
| Weight and size | Heavy and bulky | Light and compact |
| Conversion efficiency | Lower; some energy is lost as heat in the transformer | Higher |
| Electrical isolation | The transformer separates the DC and AC sides | No transformer separation; relies on built-in protection and correct earthing |
| Motor starting | Traditionally strong | Depends on the model’s surge rating, which can be high |
| Noise | Can hum under load | Usually quieter |
| Typical use | Older home inverters, some off-grid PCUs | On-grid inverters, modern hybrid inverters |
What UTL’s transformerless hybrids list
UTL’s current hybrid inverters are transformerless, and its specifications show what that design delivers. The 6 kVA three-phase hybrid lists 97.60% maximum efficiency. The 6.5 kW hybrid lists a 12 kVA maximum surge, which answers the old worry that a transformerless inverter cannot start a motor. The range runs from the 3 kVA through 5 kVA and 6 kVA to 10 kVA.
Which suits which system
An on-grid system almost always uses a transformerless inverter, because every point of efficiency lost is power you then buy from the grid.
A hybrid system with a battery now usually does too. Check that the surge rating covers your largest motor, such as a pump or an AC compressor; our hybrid calculator works out the inverter size from the loads you choose, starting surge included.
An off-grid system can use either. A transformer-based PCU is rugged and forgiving, and a transformerless inverter is lighter and more efficient. See off-grid systems.
What to check on any inverter
- The continuous rating, in kVA or kW, against everything you run at once.
- The surge rating against your largest motor.
- The efficiency figure, and which one it is: maximum, European weighted, or MPPT, which measure different things.
- Earthing. A transformerless inverter depends on the site being earthed properly, which is part of a correct installation.
For the rest of the choice, see how to choose a solar inverter, and browse the UTL inverters we stock.
Sources
- UTL: the inverter pages linked above, from UTL’s specifications
Questions we are asked
What is a transformerless solar inverter?
An inverter that converts DC to AC electronically, switching at high frequency, without the large iron-and-copper transformer older designs use. It is lighter, smaller and usually more efficient. Most on-grid and modern hybrid inverters are built this way.
Can a transformerless inverter start an AC or a motor?
If it is rated for the surge. Motors draw several times their running power for a moment as they start. UTL's 6.5 kW hybrid, for example, lists a 12 kVA maximum surge. Check the surge rating against your largest motor, whatever the design.
Which is better, transformer or transformerless?
For on-grid and most modern hybrid systems, transformerless: lighter and more efficient. A transformer-based inverter is heavier and less efficient but rugged, and gives electrical isolation between the DC and AC sides, which some off-grid and older systems rely on.