Inverter Selection Guide

his guide is to help select a suitable OFF-GRID or HYBRID solar inverter from our product line.  Before selecting an inverter, please be sure to consider these important questions first.

• What output voltage do I need?

  We offer 3 main types of inverters in terms of output voltage:
  220-240V Single Phase: Europe, Africa, Australia, the Middle East, and many parts of Asia.
  110-120V Single Phase (low voltage)：North America, Latin America and some parts of Asia.
  120/240V Split Phase: (same as above) this standard typically coexists with 110-120V Single Phase.

• Off-Grid or Hybrid?

  Off-Grid inverters are defined as the inverter is only able to draw power from grid for backup, when it becomes necessary.  Power flow to AC input is therefore one-directional.  Hybrid inverters however are able to extra power to grid when there is surplus PV power and therefore power flow to AC input is bi-directional.  It’s important to recognize that all Hybrid inverters can operate as Off-Grid inverters, but not vice versa.
  Important: when selecting hybrid inverters, be sure to check for any local certification required for legal compliance. 

• How much power do I require?

  This can be determined by performing a simple load analysis by adding up all the power consumption rating of all your load type.  When collecting power draw from inductive type load such as motors, pumps, compressors, power tools etc it is important to make sure you factor in the surge peak draw during startup to avoid under-estimation.  Select an inverter with power output LARGER than the total load power required  EX. if total load estimated = 4000w, we recommend using a 5KW inverter.

• What system voltage do I select?

  Once a suitable inverter model is determined, it will have a fixed corresponding DC voltage (or system voltage) in either 12V, 24V or 48VDC.  Users will need to prepare a battery bank voltage matching this.

• What type of battery should I use? And how big?

  For best compatibility, lead-acid type batteries are recommended and Gel or AGM maintenance-free types are most popular.  Many lithium-type batteries (with built-in BMS – Battery Management System) are also very popular in recent years and can work with our inverters, and compatibility can be confirmed in 2 ways: with or without BMS communication.  With BMS communication you will need to select an inverter with built-in BMS port, and also ensure that the battery’s BMS protocol is supported on the inverter.  The most common BMS brands we support are Pylontech, WECO, Soltaro, as well as LIB (which is MPP Solar protocol). Third party BMS may adopt the LIB protocol from us to ensure compatibility.  One may also opt to skip BMS communication by manually adjust the charging settings on the inverter to match with the requirement of the battery.  This is typically done by changing “Bulk / Float Charge” to the max charging voltage of the battery and “Low Cut-Off Voltage” to its minimum voltage.

  In terms of battery capacity this is expressed usually in Amp-Hour (Ah) and the appropriate size of the battery bank would depend on the energy demand of your system so this can vary greatly from one application to another.  There’s no fixed answer.  Normally we suggest no less than 100Ah on our 2-3kw/24v inverters and 200Ah minimum for our 5kw/48v inverters.  More information can be found in our Off-Grid System Sizing Guide here.

• Is BMS required for Lithium batteries?

  No.  It is not required, though recommended.  BMS standards for battery monitoring system and is a software protocol found mostly on Lithium-type batteries to carefully control charging and discharging of a battery without causing damage to itself.   Most, if not all, of our inverters offer programmable charging voltage and this is fine to use with some Lithium batteries without the use of BMS connection.  However, in a BMS-required situation, protocol compatibility is mandatory and so it is advisable for users to confirm if an inverter is actually compatible with your BMS system before purchase.   BMS compatibility is often “brand specific” and some of our inverter models support Lithium BMS systems such as Pylontech, Weco, and Soltaro.

• How much solar power do I require to use your inverter?

  The quick and simple answer is “none”.  Inverter output power and solar power are two different concepts and should not be confused together.  Solar power is merely a source of input power which can be used by the inverter for powering load or charging battery.  It is completely optional.   Every model of our inverter has a specific solar controller rating and it determines how much maximum solar power it can deliver.   For example, 3024MSE inverter has a 3kw max power output to load, but it comes with a 40A MPPT so based on 24v system voltage the max PV power = 1KW (Power Law).

• MPPT or PWM?

  There are pros and cons to both types of built-in solar charger.  MPPT is of course the newer technology of the two and is able to convert high PV input voltage without significant loss of solar power; however it is slightly more costly.  PWM type solar charger is more economical and when paired with the right specs of panel, it can just work as well as MPPT.  

• I do not have access to grid and only have generator. Is this ok?

  Yes. It is perfectly ok to run all our Off-Grid inverters without any grid input.  Generators may be used but be careful not all of them are compatible and accepted by the inverter.  We recommend using cleaner output genset like the “inverter-type generators”  and also be sure to size genset properly (recommended 150% or larger than inverter rating) to avoid power deterioration when load level increases.  For more details, please see genset requirement guide.

• What monitoring options are available with MPP Solar inverters?

  There are wired and also wireless monitoring options.
  By default, all inverters come with a bundled data cable and one can monitor inverters via direct PC connection to inverter through USB or RS232 port.  In the absence of a USB port, one can use a RS232-USB adaptor t to establish connection.  Monitoring on PC will be either SolarPower or WatchPower, depending on the model of the solar inverter.  Another way to monitor inverters is via SNMP module (sold separately) and this basically makes your inverter identifiable on a LAN network so it can be monitored in this environment.  For wireless monitoring, one can either go with WIFI module (monitoring on smartphone APP), or WIFI box (monitoring on PC browser at a portal site).  Both are optional accessories available for order.  Several newer solar inverter models alread come with built-in WIFI, so this is a very convenient feature if one wishes to monitor on phone APP, without having to source external module.

Should you require more information please click on each model name for more information, or contact our Sales Team for assistance.

Table 1 & 2- Off-Grid Inverters Comparison Chart

*many accessories have specific model compatibility. For more information please see Inverter Accessory.

Table 3 – Hybrid Inverters Comparison Chart

Common Terminology in Inverter Selection

Output Voltage Type (single unit).  Most of the inverters, unless otherwise stated, are based on either Single Phase 110-120V, or 220-240V standards.  Split phase output 120v/240v are also available on select models (LV2424, LV5048) and 3-phase output is generally available on all models that can support parallel.  3-phase output voltage may vary either as 208V P-P (based on 120V phase-neutral) or 400V P-P (based on 230V phase-neutral).

Waveform.  This refers to the output waveform type of the inverter.  Inverters nowadays typically come in two main types: Modified Sine Wave and Pure Sine Wave.  We produce only pure sine wave inverters.  Pure Sine Wave output inverters have lower total harmonic distortion and generally can power all types of load without issue. While slightly more expensive, Pure Sine Wave inverters by far have the best load compatibility than the Modified Sine Wave and are the only type we offer.

Max Continuous Power.  The most important attribute of an inverter.  This rating defines how much power output can be provided continuously to load.  When sizing an inverter with load, this should be the first thing to check.  Always size inverters conservatively.  If you expect to run a certain watt of load, it is a good practice to multiply this by 1.2 or 1.25, which not only will work as a buffer in case there is any under-estimation, but this will also be a more proper and efficient use of inverters as they are often running most efficiently at about 70 to 80% load.
note: special attention should be paid to “inductive” type load as they can draw very high surge, typically anywhere from 2X up to 8X during start-ups.  To avoid under-estimation, always factor inductive surge into your load calculation. 

Parallel.  This refers to an inverter’s ability to connect in multiple numbers in order to increase the overall output power.  Only specific models of inverters here can support parallel operation and they usually will require the installation of parallel kit (sold separately).  Depending on the model, maximum number of parallel units is either 6 (or 9).  In a parallel system, all units must be the SAME model name they will also need to be connected to the SAME battery bank. When stacked in parallel, they can be configured as single phase, split phase, or three phase systems.
note: it is possible only select models in a series may support parallel operation; please review catalogs for more detail.

System Voltage.  Also known as the DC nominal voltage rating of an inverter, this suggests the battery bank voltage at which must be configured in order to properly power the inverter. Most common off-grid system voltages are either 12v, 24v or 48v.  This is FIXED and cannot be changed.  While not necessarily applicable to all inverters, most small output inverters are designed in 12v, and as output increases, the demand for system voltage is raised to 24v or 48v in order to maintain good operation efficiency. High system voltage means lower current and also allows the use of thinner, less expensive wires.

Output Frequency.  Load frequencies come in two standards: 50Hz or 60Hz  Most countries using 220-240V follow the 50Hz standard while the 110-120V ones use the 60Hz, though in some cases there may be exceptions.  It is important to know the types of frequency your AC load runs in and ensure the inverter is properly programmed to match this frequency.   All our inverters are designed to support either 50Hz or 60Hz.

*Battery Requirement.  If battery is “optional” it means the inverter is able to operate without the use of a battery and can convert power to load directly using only PV or PV with grid.  Under battery-less operation, a warning sign may appear and stay on LCD to confirm the status.
*note: parallel operation will require battery connection at all times.

Peak Efficiency.  Inverter efficiency usually refers to the conversion efficiency of an inverter from DC source power such as battery or solar into AC power.  The higher the efficiency means less power is wasted during power conversion.

Utility Charger. Utility charger refers to built-in module that uses AC power sources such as utility or generators to charge batteries.  This feature eliminates the need of an external battery charger, and is critical during times when solar power is unavailable.

Solar Charger.  Solar chargers are battery chargers using solar panels and the stated current value (in ampere DC) refers to the “maximum” charging current that is allowed.  Solar chargers come in two main categories: MPPT vs PWM.   MPPT type chargers allow the use the higher voltage panels on lower voltage systems, as they can convert the high voltage input into elevated output current so little power is wasted.  Inverter-chargers with MPPT type chargers are also be more expensive than ones with PWM type.

Max PV Input (Voc).  This is the maximum PV input voltage allowed on the inverter.  Please do not exceed this under any circumstances and refer only to the open circuit voltage (Voc) rating on your solar panel. Be sure to exercise caution when planning your array and leave buffer in case of voltage spike in winter.

MPPT Tracker.  This refers to the number of built-in MPPT trackers or input available.  More trackers generally means larger PV array can be supported and this also ensure better maximum power point tracking performance.

Power Saving Mode.   Not all models come with this feature. Inverters with Power Saving Mode will draw far less power than sitting idly when there is no load.  The main purpose of this feature is to help conserve battery power when inverters are not doing any real work, e.g. no load or very low load.  When this feature is enabled, once load level falls below a certain threshold, the inverter will enter standby and stop operation.  If load level returns to above the threshold, the unit will resume normal operation.

Optional Accessories.  WatchPower Wifi module, Wifi Box, Remote LCD display and SNMP card/box are popular accessories for our inverters.  Some accessories such as Energy Meter, Modbus card etc are compatible only with our MPI Hybrid inverters. LCD remote display is a first generation device and therefore only works with a few select models from the HS/MS family.  For more information please seeInverter Accessory.

Genset Starter (Dry Contact). This feature is on most of our off-grid inverters as well as many hybrid inverters.  The genset starter is simply a two-wire connection dry contact which can be wired to a generator that support remote start-up functionality.  The dry contact is activated when inverters running in DC priority mode experience low battery voltage, and it will send a signal to turn on the generator in order to act as backup to load.   By definition, the dry contact does not carry any live voltage and only send signals.
note: on Hybrid inverters, grid feed must be disabled when using genset starter dry contact.

Monitoring.  Standard monitoring feature is available on almost all of our inverters in the form of WatchPower (for Off-Grid) or SolarPower (for Hybrid) through direct connection via USB or RS232 port. More than just displaying data, WatchPower and SolarPower software (for Hybrid) also allow users to program setting through PC interface and are available for use on Windows, Mac, and Linux.

Certification.  All our inverters are CE compliant so safe for use in EU and any other countries that recognize this standard.  Only MPI hybrid inverters come with additional regional certification requirement (VDE4105, VDE0126-1-1, AS4777) for grid-feedback.  VDE standards are widely accepted in Germany and many European countries.  AS4777 standards are recognized in Australia and New Zealand.