I already have 36 435 watt Trina Panels and 48v 280AH LifePo4 pack with built in BMS. I figure I need to spend another 5-7K to get a good inverter. the biggest challenge is powering the loads panel (without having to split off the panel into a subpanel i.e. critical loads panel) as we want to keep installation stupid simple. The second biggest issue is can the inverter be programmed to use the batteries after Solar PV is dark.
The theory is to utilize all the solar and battery power first, then grid only as required (Load surges, battery depleted, etc.,) all the while remaining grid tied but NEVER selling back to the grid (no permitting required). I realize that when the grid goes down so does the inverter.
Ideally (icing on the cake) you could turn off mains power in the load panel and crank up a generator to charge the batteries and have them run the loads, or use the generator input on the inverter, etc.. PROVIDED you are not connected to the grid. I realize a critical loads panel does this (in effect) BUT it requires you re-wire the existing loads panel and transfer all that wiring/breakers over to a loads panel (yet another expense and eye sore.
This is precisely what I am doing (and also precisely g the he reason I ditched the hybrid-inverter system I had all planned out).
You may have your own requirements as far as the product quality your looking for, but the SUN GTIL2 inverters will deliver the capability your looking for.
I’ve got a 560Ah 24V LiFePO4 pack which I’m able to discharge daily using only 2 1000W GTILs, but my PV array is much smaller than yours (1.14kW versus your 15.7kW).
Your 14kWh pack is exceedingly small for that size PV array.
You need to determine 2 things:
Overnight consumption in kWh
Peak generation requirements
I consume a maximum of 10kWh until morning, so my 14kWh pack is plenty, even accounting for the ~80% conversion efficiency of the GTILs.
The only loads I have exceeding the ~1.7kW maximum output of my two GTILs are:
Electric oven(3kW when element is on)
Toaster oven, coffee maker, electric kettle (each of which consume 1.5kW on one leg when their elements are on).
Use and duty cycle of all of those appliances is so low that I decided to supply what I could and draw the rest from the grid when they are being used (meaning ~50% of their compensation is being supplied by the inverter rather than the grid).
The GTILs can be stacked, so 2 per leg gives you peak output of ~3.4kW (~1.7kW per leg) and 3 per leg gives you peak output of ~5.1kW (2.55kW per leg).
At $250 to $300 per 1000W GTIL2, even maxing out a 6.8kW system with 8 is going to cost you less than 1/3rd of what you’re budgeting for a 7kW hybrid inverter system (to say nothing of the savings of not having require your loads at all - all a GTIL system requires is one new 240V circuit (dual-pole breaker like you’d use for a 240V oven or baseboard heater).
But your battery is way to small for an inverter that size. Maxed-out, a full 14kWh battery is going to last less than 2 hours generating 7kW…
I wanted my system to supply all (4) fridges/freezers all night long (which total to ~half my daily consumption).
My battery is oversized for my small array, but the system achieves those goals today and on ~2023 when we plan to purchase an EV, I will add another 1-2kW of panels and I’ll be able to supply our full daily consumption from the battery (at least the full non-heating portion - I’d need to add another 2 GTILs if I want to offset full consumption of those power-hungry appliances…).
