What does a grid inverter do in a home solar system?
A grid-tie inverter converts the direct current from solar panels into alternating current that matches the utility supply, so your home can use the power and send any surplus to the grid. It switches off automatically when the grid goes down, which is why a plain grid-tied system gives no backup power.
How does a grid-tie inverter work?
Panels produce direct current at a voltage that rises and falls with the sunlight. The inverter does two jobs. It tracks the panels' best operating point so as much power as possible is harvested, and it converts that power to alternating current. For that second step it must lock onto the voltage and frequency of the grid, and it only pushes current out in step with the utility waveform.
Inside the house, the inverter's output joins the electrical panel. Appliances draw first from the solar supply, and the grid tops up what is missing. When panels make more than the house uses, the surplus flows out through the meter. How that surplus is credited depends on your utility and province, as explained in Alberta net metering and the microgeneration regulation.
Why does a grid-tied inverter shut off in a blackout?
Standards require grid-tied inverters to stop exporting when the grid goes quiet. This anti-islanding protection stops your panels from energising lines that utility crews believe are dead. The shut-off is automatic and fast, and the inverter restarts after the grid has been stable for a set period.
The practical result is that a standard grid-tied array does not keep the lights on during an outage, even on a sunny day. To ride through an outage you need a battery and an inverter designed for backup operation, which is covered in solar systems during a power outage and solar battery storage in Canada.
What are the main types of grid inverter?
Three layouts cover most homes. A string inverter handles a group of panels wired together and is the simplest and often the least costly. Microinverters sit behind each panel and convert power locally, which helps on roofs with shade or several orientations. Hybrid inverters add a battery connection so the system can store and back up power. Each has trade-offs for cost, monitoring and repairs, set out in solar inverter types explained.
Most Canadian houses have a single-phase 120/240 volt supply, so a single-phase inverter fits. Three-phase models are for larger commercial services. Confirm the supply type with your electrician before you compare quotes.
How is a grid-tie inverter different from an off-grid one?
An off-grid inverter creates its own supply from a battery bank and does not need the utility. A grid-tie unit depends on the grid as its reference and as its backstop. The decision between the two systems is explored in grid-tied versus off-grid solar and in off-grid solar in Canada. If the system is small and charges a battery directly, a solar charge controller may be the part you need instead.
What should you check before choosing one?
Start with the certification. Equipment connected to the grid in Canada must be approved by a recognized testing body, and your utility must approve the interconnection. Next, match the inverter size to the array. Many designs run panels at a slightly higher total rating than the inverter, because panels rarely hit their peak output. Look at the warranty length, the monitoring app and how repairs are handled, since an inverter commonly needs replacing before the panels do.
Ask the installer which standards and utility approvals apply where you live, and compare the equipment lines in quotes using how to compare solar panel quotes. Afterward, monitoring shows whether the inverter performs as expected.
Quick answers
What does a grid-tie inverter do?
It converts direct current from solar panels into alternating current that matches the utility supply, so the home can use the power and export any surplus to the grid.
Can a grid-tie inverter work without the grid?
No. It needs the grid signal to operate and shuts down in an outage. A hybrid inverter with a battery is needed for backup power.
Is a hybrid inverter the same as a grid-tie inverter?
A hybrid inverter does the same grid-tied job and also manages a battery. It can often provide backup power when the grid is out, if it is installed for that purpose.
How long does a grid-tie inverter last?
It commonly lasts a shorter time than the panels, so many owners plan for one replacement over the life of the system. The warranty and manufacturer documents give the figure for each model.