Solar panels make direct current. Your home and the grid use alternating current. The inverter converts one to the other, and how it does that shapes cost, shading tolerance, monitoring and how long you wait before something needs replacing. There are three common designs, and a good installer should be able to say why they chose yours.
This article sits with our other pieces in panels and equipment.
String inverters
In the classic layout, panels are wired in series into strings, and a single inverter, usually mounted on a wall in the garage or basement, converts the combined output.
Strengths are simple and real. It is usually the lowest-cost option per watt, there is one box to service, and it sits in a sheltered place rather than on the roof. Weaknesses come from the series wiring. Panels in a string behave a bit like a chain, so heavy shade on one panel can pull down the output of the others on that string. Mixed orientations on the same string also lose some production.
On a simple, south-facing roof with little shade, a string inverter often performs very well. A 6 kW system on a clean gable roof is the classic case.
Microinverters
A microinverter sits behind each panel (or pair of panels) and converts to AC right there. Each panel operates independently, so shade or dirt on one has little effect on its neighbours.
That helps when you have a roof with several faces, chimneys, dormers or trees that cast moving shadows. Panel-level monitoring is built in, which makes it easy to see if one underperforms. Because there is no long run of high-voltage DC on the roof, some owners and fire services like the safety profile. Rapid shutdown requirements in the electrical code are also easier to satisfy.
The costs are higher purchase price, more electronics on the roof, and a repair job that means going up there. Manufacturers often offer longer warranties on microinverters than on string inverters, which narrows the gap over a long ownership period. Read the details in our guide to solar panel warranties.
Power optimizers
Optimizers are a hybrid. A small device at each panel adjusts the electrical output and passes DC to a central inverter. You get panel-level monitoring and much of the shade tolerance of microinverters, while the heavy conversion still happens in one box that can be mounted indoors.
Cost usually lands between the other two. You still have the central inverter lifespan to plan for, so the optimizers can outlast the inverter and keep working with a replacement unit if compatible.
Side by side
| Feature | String | Microinverter | Optimizer + inverter |
|---|---|---|---|
| Typical upfront cost | Lowest | Highest | Middle |
| Shade tolerance | Weak | Strong | Strong |
| Panel-level monitoring | No | Yes | Yes |
| Electronics on roof | None | Yes | Yes |
| Typical lifespan | About 10 to 15 years | Often longer warranty | Inverter 10 to 15 years |
| Best for | Simple unshaded roofs | Complex, shaded roofs | Partial shade, mixed faces |
These are generalities. Individual products vary, so use the table to ask questions rather than to settle them.
Cold, snow and heat
Canadian winters are not a problem for good equipment, but they are a design condition. Check that the inverter’s rated operating temperature range covers your coldest nights and that outdoor units have suitable enclosure ratings. Roof-mounted electronics live through freeze and thaw and summer heat for a long time, so ask about the temperature range and the warranty covering it. Our guide to solar in Canadian winters covers how cold affects the whole system.
Heat matters too. A string inverter in a hot, unventilated attic can derate itself, so ask where it will be mounted.
Lifespan and cost over time
Inverter life is roughly 10 to 15 years, and the panels commonly carry performance warranties of about 25 years, so it is wise to expect at least one inverter replacement on a string system. A microinverter system spreads the risk across many small units, and failures are cheaper per unit but may be harder to reach. When comparing quotes, add an allowance for replacement to the long-term cost, as discussed in our piece on solar costs and payback.
How to choose
Start with the roof. If it is simple and open, a string inverter keeps cost down. If there is shade for part of the day, several roof faces or an array you may expand, ask for microinverters or optimizers and compare the extra cost with the expected extra production. Our article on solar panel types covers the other half of the equipment decision.
Whichever design you pick, confirm the equipment carries recognised certification such as CSA marks, that your installer is licensed, and that the system includes the rapid shutdown the electrical code requires. A yearly look at the monitoring data, together with the checks in our maintenance checklist, will catch most problems early.
Quick answers
Are microinverters better than string inverters?
Not always. They help where shading or multiple roof faces reduce a string's output, but on a simple, unshaded roof a string inverter often gives similar production for less money.
How long does a solar inverter last?
Roughly 10 to 15 years is typical for string inverters, while microinverters are often warrantied for longer. Check the warranty length and who handles replacement.
Do power optimizers need an inverter too?
Yes. Optimizers sit at each panel and condition the power, but a central inverter still converts DC to AC for your home and the grid.