Solar inverters – the heart of your self-sufficient power supply
A solar inverter converts the direct current (DC) generated by your solar modules or batteries into mains-compliant alternating current (AC). Whether for the photovoltaic system on the roof, the self-sufficient garden shed or the motorhome – no 230 volt device runs without an inverter. Our team from Cleebronn (Baden-Württemberg) will be happy to advise you on +49 7135 7194106 or by e-mail at [email protected].
The most important inverter types: pure sine wave, modified sine wave and hybrid
In principle, inverters are distinguished by their output waveform: pure sine wave delivers a clean voltage curve like from the socket, modified sine wave a stepped approximation of the voltage. There are also off-grid inverters for stand-alone systems and hybrid inverters, which can simultaneously charge batteries and feed into the grid.
Pure sine wave inverters
These devices produce a perfect sine wave voltage (230 V / 50 Hz) with a total harmonic distortion of less than 3 %. They are suitable for all sensitive electronic devices such as laptops, televisions, pumps or compressors. Modern pure sine wave inverters achieve efficiencies of 90–95 %. Typical input voltages are 12 V (for small systems up to approx. 2000 W), 24 V (up to 3000 W) and 48 V (for high-power systems from 4000 W).
Modified sine wave inverters
These lower-priced inverters produce a block-like alternating voltage with voltage steps (often ±230 V, 0 V). They work with many resistive loads (incandescent lamps, fan heaters), but can cause humming, overheating or malfunctions with inductive loads or sensitive electronics. The efficiency is around 80–85 %.
Off-grid inverters (stand-alone inverters)
Off-grid inverters work independently of the public electricity grid and draw their energy directly from a battery bank. They usually have an integrated charger (inverter charger) and can optionally support an emergency power generator. Typical rated powers range from 500 W to 5000 W. For charging the batteries via solar panels, an additional solar charge controller (MPPT or PWM) is required.
Hybrid inverters
These multifunctional devices combine the functions of a grid inverter, a battery management system and an emergency power changeover switch. They can simultaneously feed solar power into the house grid, charge batteries and maintain the supply in the event of a grid failure. Depending on the model, hybrid inverters work with high-voltage (e.g. 48 V) or low-voltage batteries (12 V / 24 V).
How to find the right solar inverter – power, voltage and connection
Choosing the right inverter depends on several factors. The following checklist will help you decide:
- Required continuous power (watts): Add up the power consumption of all devices operated at the same time. For a motorhome fridge (80 W), LED lighting (30 W) and a charger (50 W), 300–500 W of inverter power is already sufficient.
- Peak power (short-term overload): Electrical appliances with inrush current (e.g. fridge compressor) often need 2 to 3 times the rated power for a few seconds. Pay attention to the peak power rating of the inverter (e.g. 1000 W continuous / 2000 W peak).
- Input voltage (DC): 12-volt systems are ideal for vehicles and small installations up to 2000 W. 24-volt systems reduce line losses and are recommended from 2000 W upwards. 48-volt systems are used for large solar installations.
- Waveform: Pure sine wave for all common household appliances; modified sine wave only for robust power tools and heating appliances.
- Efficiency: Look for a high European efficiency (at least 90 %) to minimise energy losses.
- Safety functions: Overload, overheating and undervoltage cut-off protect the inverter and battery from damage.
| Type | Power range | Waveform | Efficiency | Use |
|---|---|---|---|---|
| Modified sine wave | 150 W – 3000 W | Stepped voltage | 80–85 % | Simple tools, heaters |
| Pure sine wave | 300 W – 5000 W | Sine wave (THD <3%) | 90–95 % | All household appliances, consumer electronics |
| Hybrid (off-grid) | 1000 W – 8000 W | Pure sine wave | 93–96 % | Off-grid installations with battery and mains backup |
Inverters and batteries – the perfect duo for power supply
An inverter is only as good as the energy storage that supplies it. Whether AGM, gel or LiFePO4 batteries – the right battery technology has a major influence on the runtime and service life of your system. A 100 Ah AGM battery (such as our AGM battery 100Ah) delivers a stored energy of around 1200 Wh at 12 V. With a 500 W inverter and a consumer drawing a constant 400 W, the usable time (at 50 % depth of discharge) is around 1.5 hours. A LiFePO4 battery of the same capacity, by contrast, can draw almost the full 1200 Wh – the runtime doubles.
For larger consumers or longer periods of self-sufficiency, we recommend 24 V or 48 V systems. Our 12-volt battery guide helps you choose the optimum battery. We explain the differences between the technologies in detail in our AGM, gel and LiFePO4 comparison. And anyone who wants to charge their battery correctly will find practical tips in our guide to charging a 12V battery.
Inverters for motorhomes & camping – mobile and self-sufficient
A reliable power supply is essential, especially when you are on the road. With a pure sine wave inverter you can also run sensitive on-board electronics such as laptops or coffee machines. For installation in a camper, compact devices with remote control and low stand-by consumption (< 0.5 A) are suitable. Combine the inverter with a suitable solar module and a charge controller – our complete solar kit for motorhomes contains everything you need for an easy introduction to mobile solar energy.
Tip: Make sure there is good ventilation and never mount the inverter directly on the battery, to avoid oxyhydrogen explosions. A sufficient cable cross-section (at least 16 mm² at 1000 W / 12 V) is essential.
Installation and safety – how to connect the inverter correctly
Professional installation protects against damage and accidents. Use short, as thick as possible cables between the battery and the inverter to minimise voltage drops. For a 1000 W device at 12 V, we recommend a cable cross-section of 25 mm² for cable lengths up to 1 m. A fuse (ANL or MIDI) directly at the battery terminal is obligatory – size it at 1.5 times the maximum input current (e.g. 125 A at 1000 W / 12 V). The inverter requires a stable, horizontal mounting with at least 10 cm of free space around the ventilation slots.
Important: Reverse polarity can destroy the inverter immediately. Observe the polarity and connect the battery first, then the inverter. Use the device's earth connection to establish equipotential bonding. All electrical work must only be carried out by qualified personnel.
Frequently asked questions about solar inverters
What is the difference between pure and modified sine wave?
A pure sine wave inverter produces a voltage curve that corresponds exactly to the mains voltage. This means all devices can be operated without interference. Modified sine wave inverters, on the other hand, deliver a stepped voltage that can cause humming, picture interference or even damage in sensitive electronics. For computers, pumps and audio systems, a pure sine wave is strongly recommended.
Can I connect an inverter to any 12V battery?
In principle yes, as long as the battery provides sufficient capacity and a sufficient discharge current. For a 1000 W inverter at 12 V, over 80 A flows briefly. A starter battery is not designed for this – use cycle-resistant AGM, gel or LiFePO4 supply batteries. Further information on choosing a battery can be found in our AGM battery guide.
How long can I operate devices with a 100 Ah battery and an inverter?
The runtime depends on the connected load. A 12 V / 100 Ah battery stores 1.2 kWh. With a continuous load of 300 W (approx. 25 A) and a discharge to 50 % (for AGM/gel), this results in about 2 hours of operation. With a LiFePO4 battery, you can use almost 100 %, which extends the time to about 4 hours. A calculation example: 100 Ah × 12 V = 1200 Wh / 300 W = 4 h (theoretical); with depth of discharge and efficiency, realistically 2–3.5 h.
What does the power rating in watts and VA mean?
The active power in watts indicates how much actually usable power the inverter delivers. The apparent power in VA (volt-amperes) also takes into account the reactive power with inductive loads. Modern pure sine wave inverters usually have a power factor close to 1, so watts and VA are approximately equal. Nevertheless, pay attention to both figures, especially with motors and power supply units.
Can I connect my inverter directly to solar panels?
No, inverters require a stable DC voltage source. Photovoltaic modules deliver voltages that fluctuate greatly depending on solar irradiation. Therefore use a solar charge controller that converts the voltage into a charging voltage suitable for the battery and controls the charging current. The inverter is then connected to the battery.
What is a hybrid inverter and when is it worthwhile?
A hybrid inverter combines a solar inverter with a battery charger and a mains changeover switch. It can use solar power primarily itself, store surpluses in batteries and switch to mains supply when needed. This is worthwhile if you want to maximise your self-consumption and remain supplied during a power failure. However, hybrid inverters are more expensive to purchase and usually require a 48 V battery bank.
Which fuses do I need for my inverter?
Every inverter requires a pre-fuse in the DC supply line. The rated current of the fuse should be about 25 % above the maximum input current. Calculation: Maximum DC current = rated power / battery voltage. Example: 1000 W / 12 V = 83 A → fuse at least 100 A. Use slow-blow fuses (NH, ANL or MIDI) and place them as close as possible to the battery terminal.
Do you have further questions? Our customer service is available on the telephone number +49 7135 7194106 or by e-mail at [email protected]. Visit us in Cleebronn (Hindenburgstr.