Most likely, your old inverter is grid tie only. If it is not connected to an AC power source, it won't be able to make any power. This is a safety function required on grid tie inverters to shut down if there is a problem with the grid, so you don't back feed power when someone might be working on the lines.
Having East and West panels is a kind of cool idea also. Get more power in the morning, the same mid day power, and then more in the evening again. For it to work though, you do need good sun at the morning and evening limits. I see a few of the homes around me that have their roof turned from mine using panels on the East and West sides, but they did it as an only option. It would be interesting to see their solar output across a whole day. A few on here are doing this by running parallel strings and don't even need to upgrade the inverter as the max power is no higher, but it lasts much longer.
What size are your old 190 watt panels? Could you just swap them out for modern 300 watt panels, and then upgrade the inverter. If they come and scream at you for exporting too much power, just say, the system needed service, so you "improved it". If you charge your electric car while the sun is shining, you won't export any more power, it will all go into the car's battery. Depending on what electric car you have, you may be able to (in a year or two) use the car's battery as a home storage battery. This can be done now if you have a Nissan Leaf, but the inverter to work with it is very expensive.
wallbox.com
And it look like Tesla may be starting to do this as well.
Electrek has learned that Tesla has quietly made Model 3, and likely Model Y, ready for bidirectional charging, which should...
electrek.co
My NEM agreement had both a max power export cap and a maximum KWH per month cap. But I am not even close to those limits as it is basically what my system could produce in perfect sun if I have no load on in my house at all. I have 16 x 300 watt panels, but each panel is on a 240 watt Enphase iQ7 micor inverter, so the top power I can make is 16 amps, 3850 watts. I have seen the system clip to that on very sunny but cool days in late fall and early spring. Most of the time, I peak out around 3,500 watts. My monthly export to the grid was topping out at about 10-15 KWH per day, for a monthly total of under 465 KWH's, and I am allowed to export up to 900 KWH's. I was using the rest of that power in my house, so the meter never sees it.
I have recently added a home storage battery, so I am hardly exporting anything now. Maybe 3-5 KWH's in a whole week. My system is not perfect yet and does not auto switch nicely from charging the battery to powering my house. There are other systems like a Tesla Powerwall2 or the Outback Skybox which seem to do a much better job on the time shifting. Swapping out your existing inverter for a Skybox might be a very cost effective update. Maybe a Sol-Ark as well, since you have a string inverter system, that could work very well. I am using a Schneider XW-Pro AC coupled to my Enphase inverters. It makes for a great backup power system, but the power time shifting is causing me headaches. If I had the solar panels DC charging the batteries with a Schneider charge controller, it would work better, but I think I have a decent work around, just my programming skills are a little rusty.
As for the federal tax rebate, I asked my accountant what I needed, and he said just send in the invoice for the solar system install. I got that last year, so I got the full 30%. I will also ask if he can submit the XW inverter for this year. It would be nice to get 26% back on $3,000 inverter. I spent another $3,000+ on the batteries and other hardware and wiring components, but that would be hard to show as part of the inverter system.
