question

Hi George.

'Second opinion'. eh? Mine mightn't rate that high, but for discussion.. Proviso - *no grid feed in*..

Go 48V. For when you're serious, also kit selection. Just easier..

5kVA seems fair for your usage. The 'Mutigrid' model was a one-off, and only 3kVA. Replaced by the Multiplus II (up to 5kVA). Also Quattro in bigger sizes. Take your pick, features, etc.

I like simple, the KISS principle. With no grid export, why do you need ESS? Your grid supply could just be looked upon as a generator alternative.

Your 32m distant 'sensor' shouldn't matter. Not needed.

You don't say much about your pv, especially whether dc- or ac-coupled. Your new array distant too? May need ac kit? Might matter.

Anyhows, just to kick your question off..

Hi @Apple047

This is my ESS MPII 3000 48V, LG Chem RESU 10 and ET112 battery consumption chart using the Octopus GO to charge off-peak as I have not done a full solar panel install due to the ROI being pushed out well beyond the 12 years average without FIT.

You can see where the limits of the inverter are reached at 18:00 with ovens etc., but hardly an issue and typically as a result of more than one high consumer running at the same time.

I also have a full off-grid soluton with only 8 panels and only a 77Ah battery elsewhere, but even then the MPII copes with washing machines, dishwashers etc. as long as they don't start together (initial water heating can be a culprit). The MPPT works great to ramp up and supply the heavy consumers and top up as needed with battery during the day. The battery is often charged within an hour or two. My next visit to the property will see it configured to ESS grid parallel as that avoids dealing with the occasional inverter overloads.

PS - FIT will be replaced by new microgeneration scheme in Jan 2020 for which you will get paid, but at much lower rates than when FIT was introduced. Downside is suppliers will set their own rates so don't get your hopes up. With dreadful ROI, UK renewable energy sadly remains only for those with deep pockets and who want to save the planet ;)

In summary:

• MP II 3000 will handle most consumers even modern ovens etc, but just not simultaneously. If grid parallel, that however poses no issues as the inverter tops it up with grid.
• I am personally a fan of 48V because of lower currents easier to handle and cheaper AWG for installations. (latter benefit is likely lost due to higher 48V equipment cost)
• My off-grid installation is also in the garage about 15m from the house it supplies and has absolutely no problems.
• Victron kit is designed for marine, although they have branched out into many other areas, so whatever you buy, it is going to last and serve you well.
• The image of my off-grid installation and consumption below show well Li and modern mono 300W panels can work. The sun is only in the right spot at about 13:00, but the panels are incredibly sensitive and the Lithium charges very fast. Pay close attention to that part of your setup. Feed-in for me is not an option, but just imagine how much energy is lost in my installation every day when the house is not in use. Another battery is on the agenda, but then they don't come cheap and again even with 8 occupants it will be a struggle to consume all the stored electricity thanks to everything from LED lights to fridges being very light consumers these days.
• I keep the fridges running and alarm system too as Lithium actually likes being "self consumed".

Hope this gives you some real world insights for your design.