Solar Inverters

Matrix Energy has transferred its future solar electric (PV) business to HES-PV, one of Canada’s largest and oldest PV distribution companies. With warehouses in four provinces, HES has a large inventory of the key brands of solar modules, batteries, charge controllers and inverters.
View HES' Solar Inverters at

Inverters used in renewable energy systems change the DC (direct current) energy from 12, 24, 48 VDC batteries to 120 or 240 VAC AC (alternative current) for use in residential, industrial, institutions or commercial applications. A wide range of inverters are marketed and the model that should be selected is truly dependant on the application.

Apart from the technology different manufacturers use to change this DC to AC current, inverters can be broken down into two main categories – modified sine wave and pure sine wave inverters.

different types of inverters

The output voltage wave is a pure sine wave with very low harmonic distortion and clean power like standard utility supplied electricity. In practical terms, Modified Sine Wave Inverters will power most appliance and tools while Pure Sine Wave Inverters offer electricity much like mains or utility power and are required for sensitive electronic and electrical items.

Apart from the wave form produced by the inverter, the second significant difference for users of inverters in renewable or autonomous power systems to consider is whether the inverter includes an automatic, built-in battery charger. These inverter/chargers are typical of back-up power systems where conventional grid power or a back-up generator operates in parallel with a inverter to power devices in the event of a power failure.

OutBack Power inverters
Xantrex, Schneider, inverters, products
FX seires, OutBack, sealed, inverters
XW inverter, Xantrex, Schneider, inverter

Power rating

The power that inverter can deliver is the basis of comparison since it is the main criteria for choosing an inverter.   Inverters are generally sized according to the power they can deliver, often expressed as “watts” their specifications may also be shown in Volt-Amps (VA).  This is the result of the product between the voltage (in volts) and the amperage or current (in amps).

The unit of measurement to compare the real or usable power of an inverter is the Watt. Power (Watts) = Apparent Power (VA) x Power Factor. It is necessary to know the power factor of the inverter or the efficiency of the inverter. This value between zero and one can be found in the specifications or technical data of each inverter.

Inverters without built-in battery chargers are often used in systems that already have an external battery charger or they may use a solar, wind or microhydro system for battery charging.  Inverters in this category typically range in output size of between 75 watts and 3000 watts and are used in light duty applications for recreational vehicles, marine  or mobile applications and weekend camps or cottages.

Grid-Tie Inverters

Available in sizes from 1.8 to 500 kW, Grid interactive (or grid-tie) inverters are used to change the energy derived from a solar or wind power system directly to AC power that may be returned to the mains or utility.

When the solar or wind power system produces more power than that which is being consumed at the location where it is installed, the excess electricity is sent to the utility.  Alternatively when more power is needed than the renewable energy system can supply, the utility makes up the difference.  In event of utility power failure these inverters are designed to instantly shut down ( a feature known as anit-islanding)  thus preventing power being fed into the power lines and avoiding any possible injury to workers on the power lines themselves.  Some of the ‘‘grid-tie’’ inverters include the PVI series from Solectria Renewables,GT series from Schneider Electric.

Sizing and selection of grid-tie inverters

The operational input voltage of grid-tie inverters is limited.  It is important to ensure that the output of the solar array for example falls within the maximum power point "MPP" voltage of the inverter including considerations for both hot and cold temperature extremes, available sunlight and other environmental conditions such as the edge of cloud effect.

To do so requires:
• The Vmp (maximum power voltage) of the PV array divided by 1.25 remains in the range of the inverter’s voltage during the hottest time of the year (low voltage input).
• The Voc (open circuit voltage) of the PV modules multiplied by 1.25 remains in the range of the inverter voltage during the coldest part of the year.  This factor of 1.25 represents the temperature coefficient effect on the Vmp and Voc of the solar array.

It must also ensure that:
• The Isc (short circuit current) of the solar array multiplied by 1.25 shall not exceed the maximum DC input current of the inverter.
• Ideally the ratio between the total array power and the maximum DC power allowed by inverter must exceed 50% and should be as close to 1 (100%) as possible but not exceeding the inverters maximum input power.

Inverters with built-in battery chargers are often used in isolated areas where the inverter draws its DC energy from batteries that have been charged by photovoltaic arrays and/or other sources, such as wind turbines, hydro turbines, or engine generators.  Such modified or pure since wave inverters range in size from 1500 W to 36 kW.

Where utility power is available, these inverters are used as back-up power systems.  The integrated battery chargers maintain the battery and during a utility outage, these inverters are capable of supplying AC energy to selected loads. This is ideal for telecommunications applications, small businesses, commercial applications and users who would like to avoid inconvenience during power outages such as basement flooding, loss of food in refrigerators, lack of lighting, phone or alarm systems etc.

All of our inverters with a built-in battery charger incorporate “off-line” technology.

Off-line inverters do not continuously convert DC to AC power; instead they power AC appliances in the presence of a utility grid and only switch to the battery bank for DC to AC conversion when there is failure of the grid. Most devices (servers, new computers etc.) are equipped with large capacitors capable of dealing with very short cuts to their electricity.  During a power outage however, these off-line inverters are able to bridge that millisecond delay between the failure of the utility grid and the transfer to the inverter’s battery bank.


Sizing and selection of an inverter

Inverters typically have an operating efficiency curve that peaks near 95%, corresponding to its maximum continuous rating.  That is to say that to deliver 1000 watts of power to a microwave, for example, they will consume 1052 watts of energy from the battery (1000 divided by 0.95 respectively).  The closer the inverter works to its continuous power the more efficient it will be, the opposite is also true!

To determine the power of the inverter:
• For resistive loads, add all the power ratings of the AC appliances that will be connected to the  inverter together and multiply this sum by a safety factor of 1.20. This 20% safety factor should ensure that the inverter doesn’t get overloaded by the appliances should they all run simultaneously.   For example if the total of all devices connected to the inverter is 400 watts, the power of the inverter must be equal to or greater than 400 W x 1.2 = 480 W.
• For capacitive and inductive loads (motors, microwaves), add all the power ratings of these loads and multiply by a factor of 2 or 3 while ensuring that the maximum current of the inverter is equal to 4 or 8 times the total current of the loads (inductive and capacitive). Why?  When voltage is applied to a motor, the torque related to the current required to start the motor is very high at the beginning so it is therefore necessary to ensure that the inverter has the ability to provide the surge current needed over a period ranging from few milliseconds to few minutes depending on the motor.

During power failures, the inverter with a built-in battery charger can automatically anc continuously provide electricity to all major appliances such as fridges, freezer or computers, pumps, furnace motors, alarms, phone and lighting, etc.. The batteries can be sized to meet the energy needs for the duration of the prolonged power outage from minutes to days.   GFX, FX, VFX Series from OutBack Power, MS & MS-AE series from Magnum Energy Inverters XW Series and TR Series Inverters from Schneider Electric, formerly Xantrex, are available with built-in battery charges.

Among these types of inverters, the GFX series from OutBack and the XW series from Schneider Electric, formerly Xantrex, are able to return the excess electricity generated by the DC source to the power company when configured in the “Sell mode”.  In this configuration the user may reduces their electricity bill where time of day billing is in effect.   Both of the GFX and XW series have all the anti-islanding protection devices built-in and the ability to synchronise with the utility’s wave form. In the event of a power outage, the inverter will powers only the local critical loads and will not return power to the grid.

Some typical power equipment

The parameters important to know when selecting inverter are: total power rating of AC load; the type of loads and the hours of operation for each load. These parameters will help to choose the size of the inverter and related components (batteries, cables, protection devices and others) that are needed.

Description home appliances
Typical Wattage (in watt)
Description home appliances
Typical Wattage (in watt)
Air Compressor - 1 H.P.
Lighting - Comp Fluorescent - 23 watt
Air Conditioner - 5,000 BTU
Lighting - Fluorescent 2 bulb
Air Purifier
Lighting – Halogen
Answering Machine
Microwave Oven
Christmas Lights - 100 Small Bulbs
Mixer – Stand
Clothes Dryer - Electric
Refrigerator - 17 cu. ft – Frost free
Computer Printer (Printing)
Television - 32 inch
Computer with Monitor
Television Plasma 42' - 50'
Exercise Equipment - Treadmill 3 H.P.
Television/DVD/VCR Combination
Freezer - Upright/Chest 17 cu.ft. - Frost free
Toaster Oven
Grill - Counter Top
Vacuum – Regular
Hair Dryer (Hand Held)
Video Game

Inverters -FAQ

Why are some inverters much more expensive than others?

In general, these differences are related to options:
- Surge, peak power capacity
- Adjustability of the voltage sensitivity of the trigger voltages
- Automatic restart of the battery charger after inverter shutdown
- Adjustability of battery charger setpoints
- Overload protection
- Remote configuration of operating modes (start automatic generator, energy Management)
- Expandability via the coupling of multiple inverters
- Inverter efficiency
- Grid connectivity
- Monitoring cababilit; data access
- Wave form; modified vs sine wave

Protection devices and choice of cable:
DC Fuse: Fuses and breakers are required to safely isolate the battery and inverter. Class T fuses are generally used. Consult the inverter fuse table included in each Matrix Energy catalogue.

DC Breaker: A DC breaker is used to For the selection of circuit breakers, divide the power of the inverter by the nominal battery voltage and multiply the result by 1.25. For example - a 12 V, 2000 W the circuit breaker should have a minimum current capacity of (2000 W / 12V) x 1.25 = 208 A. As 208 A circuit breakers do not exist, the next closest choice is a 250 A size. Only DC rated circuit breakers of 125 VDC - 600 VDC should be used.

Cables: The electrical current flowing between the inverter and batteries is extremly high; therefore it is necessary to use flexible stranded copper cables with a resistant outer jacket designed for this application. If a small gauge wire or cable is used, the voltage drop will be significant and the inverter will not work properly, or fire may result. A table specifying the sizes of cable and maximum lengths are in the Cable section of our catalogue.

Grounding: It is strongly recommended to protect the inverter against surges caused by lightning using the ground terminal connection or the GFCI installed on the inverter.

What is a “Powerboard”?
Matrix Air Heating Inc. offers pre-assembled control panels known as a "Powerboard or E-panel'' that includes the inverter and disconnects and fused protection all pre-wired and installed on a metal or non-metallic backplate. This reduces installation time and configuration by the user before delivery because everything is pre-assembled according to the code and pre-tested prior to shipment. All that remains to do is connect the photovoltaic array or wind turbine, loads and the battery bank. Options do vary, though most "Powerboards" include:

Up to four inverters; AC and DC conduit box;DC breaker; manual bypass switch; array DC breaker (option); DC and AC bus bars; DC and AC wiring; ground bus bar; spaces for up to six AC breakers; 500 A - 50 mV shunt for battery monitor; wall mounting plate; GFCI outlet (for Outback inverters); temperature sensor (option); remote control (MATE inclusive); all equipments is cETL certified (CSA inspection for pre-assembled panel is optional). All wiring is done in conduit within electrical drawings provided.



HES PV Toll Free: 1.866.258.0110