Inverters

About inverters

The specifications that matter

• continuous AC output in kW, which caps the load you can run at once
• surge or peak rating, which covers the brief inrush of motors and compressors
• maximum PV input and the number of MPPT trackers, which set how many panel strings you can connect
• the MPPT voltage window, which decides how many panels go in a string
• peak and weighted (European/CEC) efficiency, typically 96–98.5%
• topology — on-grid, off-grid, hybrid or micro

How to choose an inverter

• Size the inverter against the loads you need to run simultaneously, not against the total wattage of every appliance in the building — a 5 kW inverter comfortably runs a fridge, fans, lights and a couple of ACs, but not all of them plus a water pump starting at the same time.
• Keep the panel array between roughly 1.0 and 1.3 times the inverter's rating. Slight oversizing (a higher DC-to-AC ratio) captures more energy on cloudy mornings and winter days; going far beyond it wastes generation through clipping.
• Check the surge rating if you run motors — deep-well pumps, compressors and older air conditioners can draw two to three times their running current for a few seconds at start-up.
• Choose a hybrid inverter if a battery is in your plan now or later; retrofitting storage onto a pure grid-tie inverter usually means buying a second unit or an AC-coupled battery system.
• Confirm the inverter is approved by your local utility or distribution network before you buy if you intend to export power — grid connection depends on certified anti-islanding and local grid-code compliance, not on the inverter's specifications alone.
• Match the battery communication protocol (CAN bus or RS485) between inverter and battery. Compatible voltages are not enough; without a supported protocol the battery management system and inverter cannot agree on charge limits.
• Look at the warranty term and what it covers. Five years is the common baseline, ten is offered by stronger brands, and extensions are often cheaper bought with the unit than later.

Common mistakes to avoid

• Buying on peak-watt price alone. A cheap inverter with a narrow MPPT window forces awkward string layouts and can strand a portion of the array.
• Ignoring the ambient temperature rating. Inverters derate in heat, so a unit rated 5 kW at 25 °C may deliver noticeably less on a hot roof-adjacent wall at 45 °C.
• Assuming any grid-tie inverter keeps the lights on during an outage. Standard on-grid units shut down for safety unless they have a dedicated backup or islanding output.
• Overlooking the IP rating. An outdoor installation needs at least IP65; indoor-rated units mounted outside fail early.

Frequently asked questions