Hybrid, string or micro inverter: which one is right for you?
In short: The inverter converts the modules’ direct current into alternating current for the home and the grid. If a storage system is to be added now or later, a hybrid inverter is the obvious choice. Without storage, a grid-tied string inverter is enough. Micro inverters sit directly on one to four modules and are the solution for balcony power plants. Off-grid inverters supply systems with no grid at all.
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What types are there?
Solar panels generate direct current. The domestic grid and the public grid operate on alternating current. The inverter sits between them: it converts the current, continuously seeks the operating point at which the panels deliver the most power, and synchronises with the grid. The choice of design depends primarily on one question: should a storage system be included?
| hybrid inverter | Grid-tied (string) inverter | micro inverter | Island inverter | |
|---|---|---|---|---|
| Storage device connectable | Yes, separate battery input | no | no (own balcony storage units, see below) | Yes, with a 48 V battery |
| Network | connected to the mains | connected to the mains | connected to the mains | without mains power |
| Power in the product range | 0.8 to 29.9 kW | 0.8 to 125 kW | 800 to 2,000 W | 3.5 and 6 kW |
| Phases | single-phase or three-phase | single-phase or three-phase | single-phase | single-phase |
| typical of | Roof-mounted system with storage tank or storage tank to be added later | Roof-mounted system without storage, commercial roof | Balcony power plant, individual modules | Garden shed, hut without mains connection |
Information current as of: ACTEC product range, October 2026. The specifications for individual devices can be found on their respective product pages.
What is a hybrid inverter?
A hybrid inverter has a battery input in addition to the module inputs. It charges the storage system with surplus energy and discharges it when the modules are not supplying enough. The batteries it accepts are listed in its storage list; only those listed there are approved. A hybrid inverter may also be a suitable option if the battery is to be installed at a later date: in that case, the inverter remains in place, and the battery modules – along with a BMS unit, depending on the system – are added later.
Many hybrid devices also have an output or a switch for power failure. The device’s data sheet specifies exactly what is supplied in this case and what additional requirements apply.
The devices are listed under ‘hybrid inverters’; those with a suitable storage unit are listed under ‘Storage inverter sets’.
What is a string inverter?
A string is a series of modules connected in series. The grid-tied inverter accommodates one or more strings and provides grid feed-in for any surplus power not required by the house. It does not have a battery input. It is the straightforward choice when storage is definitely not planned, and is the standard option on large commercial rooftops.
If a storage system is to be added at a later date, the inverter remains in place, and an AC-coupled storage system with its own inverter is installed alongside it; or the inverter is replaced with a hybrid inverter. Both options are listed under ‘Retrofitting PV storage’. The devices are listed under ‘Grid-tied inverters’.
What is a micro inverter?
A micro inverter is located directly behind one to four modules; each module or pair of modules has its own MPP tracker. If a tree shades one module, it does not affect the others. The devices available in the range have an output of 800 to 2,000 W and form the basis of balcony power plants; in the case of the Growatt NEO 800M-X, the inverter limits the grid feed-in to 800 W according to the data sheet. There are dedicated storage units for balcony power plants, which are situated between the modules and the micro inverter or have the storage unit built in; for more on this, see ‘Balcony power plant with storage’.
The devices are classified as micro inverters.
What is an off-grid inverter?
An off-grid inverter operates without a public grid; how it differs from backup power and emergency power is explained under ‘Backup Power’, ‘Emergency Power’ and ‘Off-Grid System’. It supplies loads directly from modules and a battery, for example in a garden shed without a grid connection. The range includes the Growatt SPF 3500 ES and SPF 6000 ES Plus. These are listed under ‘Off-Grid Inverters’.
How do you select power, MPP trackers and phases?
- Power: The inverter’s rated power is the alternating current power it outputs. The module power may usually exceed this, as the modules rarely reach their full rated power. The exact figure is specified in the data sheet as the recommended or maximum PV power. For the grid-tied inverters in the range, this is usually 1.5 times the rated power; for hybrid inverters, it is usually 1.5 or 2 times the rated power; and for some individual units, it can be up to just under 3 times the rated power.
- MPP tracker: Each MPP tracker controls its own string of modules. If modules are located on two sides of the roof, for example east and west, or if part of the array is shaded, each area belongs to its own tracker. The devices in the range have between one and twelve.
- Phases: Single-phase inverters are available in the range up to 6 kW, three-phase models from 3 kW. A qualified electrician will advise you on which model is suitable for your domestic connection.
- Efficiency: According to the data sheet, the maximum efficiency for grid-connected and hybrid inverters is up to 98.8 per cent, whilst for the available micro inverters it ranges from 96.5 to 97.3 per cent.
Who installs the inverter?
An inverter for a rooftop system is integrated into the domestic electrical installation; this is carried out by a qualified electrical contractor. The grid operator and the Federal Network Agency provide information on registration with the grid operator and in the market master data register.
Information on how to plan an entire system can be found under ‘Planning a PV system’. You can find inverters by brand on the manufacturers’ websites for Growatt, Huawei and Fronius.
