KH, do you have any storage batteries? Have you priced a bank 48V 1100Ah batteries? Do you know how much work is involved in maintaining a battery bank? Have you priced in a generator and a charger for the times when the sun is covered by clouds for more than a couple of days?

Have you priced in the cost of a new inverter that will set its own output frequency and not rely on the timing signal from the grid?

Grid connect and RAPS are two beasts of entirely different temperaments. GC is convenient for the user, RAPS generaly are not.

Firstly
You differentiate buildings where base-load power is a necessity (hospitals and airports)- and of course by scoping how much power it needs against how much power it can generate on its own of course (factories with electronics and machinery that draw far more electricity than the sum of the PV panels and turbines its property can hold).

Batteries:
Well considering there is absolutely NO 'maintenance' at all I don't see what the problem is. You buy it (they are usually thrown in as an extra with the PV Panels for most Solar deals- had you bothered to ever read one).
And once installed it functions entirely on its own.

So we are in fact talking about a very simple procedure with a one-off payment and a quarter century lifespan of automated functioning to pay itself off (which as far as today's power bills go- a very short amount of time).

KH, I was employed as technical manager at Choice Electric Co., which was the largest distributor for BP solar at the time. I have designed and maintained solar installations in locations from Moreton Island to Barcaldine and specified designs for installations as far afield as coral atols in the Pacific and Aboriginal communities in Central Australia. Believe me when I tell you that you are talking nonsense.

A typical RAPS installation requires all of the things I mentioned and deep-cycle storage batteries are not like car batteries, they require mintenance of the electrolyte and good monitoring of the state of charge. Gel cells can be used for low demnad applications, but they can't be allowed to over discharge or the electrolyte will dry out and slump, exposing the plates.

It's also not cheap.

http://www.solarpoweraustralia.com.au/remote-area-solar-power-for-your-home.html

KIng Hazza tell us;

What type of batteries you have installed and how long ago ?
How many ampere hour rating and voltage ?

You claim zero maintenance. This I find remarkable.
Lithium cells being so expensive for that type of service demand seems
unlikely. They are the closest to zero maintenance because it is a case
of chuck it for dead cells.
If we are to get past just a general waffle lets know about your battery bank.

Antiseptic is absolutely right. I have grid connected solar panels and an uninterruptible power supply consisting of 8 x 375 Ah deep cycle lead acid batteries charged from the panels. You need a changeover switch that detects loss of the grid and switches over to the batteries. You also need a separate inverter to feed the battery power into the house. I live in a rural area where grid power dropouts are much more prevalent than in a city. The switchover is so fast you don’t even know the grid has dropped out.

My batteries hold about 18 kWh so they will last a couple of days with careful usage. But relying on solar panels to charge them means that if the weather is cloudy the batteries will soon run down. If you are not connected to the grid and rely on batteries you will need a petrol or diesel generator to keep the batteries charged. Where I live there are many properties not on the grid but they all need generators to charge their batteries and probably have higher emission intensity electricity than the average city dweller. This is somewhat ironic as they are often Green supporters who want to be disconnected from the grid but are blissfully ignorant about their carbon footprint.

Sorry KH, but the batteries do need constant maintenance by checking the charge levels and acid levels. If you fail to do this it will significantly shorten the battery life which brings me to the cost.

My relatively small storage system (used for emergency only) cost over $8,000 to install two years ago and does not include the cost of a diesel generator. Whereas the cost of panels has fallen in that time, the cost of batteries and inverters hasn’t. So good luck KH with disconnecting from the grid. It is not a cheap option.

My battery bank is non maintenance deep cycle lead acid. The batteries never need topping up. The inverter cuts out at 11.9 volts, so all u use in the batteries is the saturation. The batteries charge to 14 volts. My charger consists of 3 automotive alternators, set up as wind mills. Beside the PV panels. Never run out of power, and plenty to send to the grid.
I think you lot are talking about early set ups; It doesn't take much to charge 12 volt batteries.
It also pays to convert your fridges and freezers to soft start, by adding a capacitor per appliance, the rest is easy.