AC Coupled Vs Hybrid Inverters - What's the Difference? 

A Great explanation. I've had conflicting advice from different potential installers about adding a second array and a battery to an existing FIT registered 3kW system already installed. A similar video explaing how two arrays connecting to a single battery and the grid would be very useful.

A great explanation and I appreciate that you are trying to keep this as simple as possible. With the hybrid inverter, PV to battery power flow is not "no conversion", it's a DC voltage conversion from PV DC voltage to battery DC voltage. This is more efficient than the DC/AC/DC conversion with an AC coupled system, but it's not 100% efficient, there will be some losses. With some tariffs that are available at present (e.g. Octopus Intelligent Go) it makes financial sense to fill your battery from the grid (AC to DC conversion for either hybrid or AC coupled) and then export as much of your solar as possible to the grid (DC to AC conversion with either hybrid or AC coupled) and also supply your house in the evening from battery (DC to AC conversion with either hybrid or AC coupled). In this case there is no efficiency advantage for hybrid over AC coupled because there will be little or no PV to battery power flow. AC coupled systems can make it easier for solar diverting technology (solar to immersion heater or solar to EV) although such diversion is not as economic as it used to be now that export prices have imporoved. There can be some limitations with hybrid inverters reducing PV power when tghe battery is full. No such problems with AC coupled. Hybrid systems take up less space and cost less.

Good explanation of the difference and also saves on any conversion losses.

'everything uses AC'- well that's just not true. Almost all appliances convert the AC back to DC internally. Including that TV. Only items like vacuums that have a motor use the mains AC. And that could be replaced with a smaller, safer DC motor (for example the cordless vacuum). AC was implemented as an efficient means of transporting power over long distances. It's a shame we have to still live with it in our homes (in the modern era) as it is much more likely to cause fatalities, and also means every single appliance has a switched mode power supply built in as a necessity.

I currently have solar only. (Well, I have an EV with a bidirectional charger too, so technically from that point of view, I do have an ac-coupled battery.) The system is two years old, and it is a single inverter in my loft that doesn't need scaffolding to get to. I think I would consider getting the inverter replaced with a hybrid inverter with batteries when it's near the end of its life, so maybe in around 8-10 years, but I'll have to look at the case in detail; I'm on octopus flux right now and the energy is worth more if exported between 16:00 and 19:00 (some of my solar comes in during that period anyway), but I think the main ROI comes from just the solar - however the inverter is a 3.6kW model to be compliant with G98, and the solar panels are 4.7kWp, so a beefier hybrid inverter might be able to take more of the energy at peak times and charge a connected battery while limiting the grid output to 3.6kW to remain compliant with G98. I wouldn't simply trust what an installer has to say; they have a vested interest in selling their system, and their goals may not be fully aligned with mine. Having said that, I'm an engineer and I like to look into the detail. It's good that VAT on battery-only installations has now been lifted.

When you compare your solar output (hybrid inverter) with Harry's new solar panel's output (AC coupled) shouldn't you allow for his efficiency losses caused by the his extra double inversion?

Hi, Sorry, could you please confirm what's "DB" in your diagram? Thanks.

Thank you, you should give a power consumption comparison too. It is pretty big.

Great explanation, keep up the good work.

Why no EV mentioned?

Why is the quality of the image so bad? It's not the YouYube resolution that's on HD