Are Delta inverters any good?  

Delta have a limited inverter range, but what they make is solid. Substance over style.

The single phase H5A-222 5kW inverter is rated at 5kW AC output but the three phase 5kW RPI-M5A model is rated at 4.99kW.

Might not seem much, but 4.99kW presents a problem with today's popular 370W size of solar panel.

18 x 370W = 6.66kW, that's what most people want to qualify for the Government subsidy on solar panels worth about $3,500

The rule is you take that panel power, 6660W and multiply by 0.75 and the inverter must be able to be rated to whatever that number is.

6660 x 0.75 = 4.995kW. That's 5W more than the Delta RPI rating, so you have to choose a different inverter or different panels.

That issue aside, Delta inverters are good.

In fact the H5A-222 has a couple of very good and unusual features.

The consumption energy meter is built-in. Other inverters have an optional extra $100-$150 energy meter that goes in your switchboard with a CT clamp around your main input cable.
It measures the flow of current in and out of your house so in the reports you see all sorts of extra and useful things like self-consumption of solar, exports, imports, and it operates 24 x 7

The Delta in-built energy meter goes some way towards the slightly higher than normal price for this class of inverter.

The other 'selling point' is a very low start-up voltage. This gets the inverter going moments earlier than other inverters and in theory gives you some extra power, but in reality, it's not really going to make the slightest difference.

Delta also have a single phase 'solar + battery' inverter, the E5 that works with the Delta battery. We have never sold one with a battery connected, so it would be wrong to comment one way or the other about it.


Delta have provided a full parts and labour 10 year warranty on their inverters for years.

We sold the unstable Delta Solivia model back around 2013-2015, and whilst it had a fairly high failure rate, as many did back then, there's no denying how excellent Delta have been providing what appears to have been brand new replacements, no matter the age.

We replaced one in January 2021, still in warranty, and a new inverter was sent from Melbourne to replace a model we installed in 2014. Some people might expect that, but I can assure you, only a handful do that. It's usually a refurbished one with the other manufacturers.

This review was written by Andrew MacKeith, Solar4Ever service manager since 2011.