How does this work?
You probably have a small UPS attached to your computer (should have) which kicks in if the grid goes down so you can shut down your computers without losing everything, they also condition the power so you get nice power ( the grid is not so great) and of course you get various levels of protection.

With a home sized ups they work the same, most will allow you to power by solar so you reduce your bill that way, but they don't always allow you to use the battery as power - because this is for when the power goes out...
think of it as  grid tied solar which works without the grid.

Yes most grid tied and many hybrid system shut down when the power goes out. A point missed by many people who have solar installed.

IMPORTANT
When you have this type of installation, you need to  consider two important factors.
1. the pass through.
2. inverter size.

The pass through is  where the inverter passes the grid power to your home. this can be limited and may not meet your needs.
it may be 4000w of power, it may be 14000w, but this needs to meet your peak loads within your home.

The inverter size and depending on the actual configuration/type, will depend on how much power your going to need from the inverter. As you wont notice power outages, it can be problematic to have a smaller inverter as it will cut power if your load is too high. So you need to consider what power the inverter would be;
5kw is good, 8kw is going to meet most needs 16kw is going to supply everything.

You could go down to a 3.6kw, as this will run most homes with lower power usage.
This may also be tied to the power pass through, so keep that in mind.

What we were going to say in the post was that if you have teenagers the internet going down can be a big issues and cause you a headache, so it pays to have a back up. We do make a small UPS for routers, as the internet has back up power, such as mobile internet and often cabled internet works too.
That's to say if your power goes off,  the internet is still there and working so you just need power.

If you want to test this, go turn off your router/modem for a few hours and you will see how much you will need to do something 🤣

POWER SAVING:
These systems work with what's called priority; this means that your battery is charged, the excess solar is provided to the home.
You have modes, like SBU - this is the better mode as your home gets solar power, any short fall comes from the battery, and failing those it comes from the grid.
it can have USB and SUB, for back up (UPS) it is likely to be using SUB mode.
You may want to change this, but you would never know when you will have a power cut, so changing the mode would more relate to which season you are in.

For example SBU when you have plenty of solar. USB when you do not.

You do need to pay attention to the unit as some wont charge from the grid while providing power. its is likely that in winter you would need to grid charge if you were using  SBU mode.

Is it Grid parallel? do I need a G99/98/100?
These are NOT grid parallel and you do not need to fill out paperwork and ask permission. The ENA and G** is ONLY to address system that work in parallel with the grid ( together with) meaning out putting power onto the grid. these are more like an appliance, such as a oven or welder. Therefore you do not need to apply and pay for connecting the device.

How do you wire this up?

Wiring it into your home is not too complex but has its dangers.

I would have a back up just in case you have a fault in the system. This will mean having a transfer switch.

Working  from the other way you would connect the transfer output to the fuse box where the cables from the meter go to.
This then goes to the transfer switch out.
Then on the transfer switch you would have the grid cables ( from the meter) on one side and the inverter the other.

This then gives you the option of output from the inverter or grid to the fuse box.
You do need to install a earth (PE) for the inverter side.

You would then need to wire from the grid supply to a smaller consumer unit, which is then wired to the AC input of the inverter.
this needs to be a "full load" connection (tails).

This is just a summary of how to wire and not detailed nor does it cover all issues and safety, so keep that in mind, you could be working with live grid power and there is a risk of shock or death and a host of other problems.. IF IN DOUBT GET THE PROFESIONAL OUT!

Any other questions?

Lets get this started right as people have very much a misinformed view of how this works or would not and what saves money.
Grid tied inverters will NOT work when the grid goes down.
Grid tied inverters only save you what you can use.
Grid tied is cheaper.
Grid tied can be limited.
Grid tied has ongoing fees.

Off grid gives you independence.
Off grid works, even without the grid
Off grid is robust and costs less than the grid tied equivalent. 
Off grid is less limited.
Off grid is a one off cost.

Grid tied is parallel and off grid is not, this difference can make a difference when it comes to integration or you can just switch over.
Off grid starts usually with a shed, garage or workshop being taken from the grid, or it may not have had any power. it seems logical to "test out" solar and how it works with a "small project" but it often grows very quickly - you have been warned!

The benefit of a off grid is that they are grid forming ( makes the power) so if there is a power cut you still have your lights on. but you can be integrated into your home with transfer switches, if you know what your doing. For example your lights, you could run a cable to the lights  and switch between off grid and on grid lights.
This is probably the easy option as a modern light circuit is low power, each energy bulb is around 6watts. You will probably use more power running the inverter over the actual load.

You may also want to run a set of sockets off solar with its own circuit, this is a little more work chasing (laying) cables and finding green sockets or something to distinguish the two power source. you would want to do this as you don't want to run a load of extension cables all over the place. trip hazards and messy.

One benefit is that you can have a larger inverter as you do not have to meet G98 or G99 regulations as its not parallel with the grid, so you can grab a 5kw inverter and run your power. I would suggest that you  know about electricity before you start and make a plan.
you would want to  have the output fused, you may want to them have a distribution unit, and then run a suitable cable to the home, where you will distribute the power as required and safely.

when it comes to  grid down, its important to not cause a grid and off grid scenario as there is magic smoke and a smell that takes ages to go away. you would want to pull the tails ( the big cables) and place these in a transfer switch so you have the grid on one side and your off grid on the other. This also means planning for running the house and its power demands.

Going off grid for your power requirements totally is not going to be that fun with in the UK due to the feast and famine, but as we work with many off grid installations is not that hard or involved. you will need to have a generator. red diesel would be ideal, and you simply charge the battery with the generator and this can also supply the load. With charging required to various degrees over the year, you are looking at around 90 days where solar may not be the best. you would want to over size the battery if you are off grid so that you can get the most of the 80% faster charge area of the battery. 

Solar should be set up accordingly as south roof mounts are not going to cut it. You will need to set up a winter array for sure, and spread the time of the peak. this would need a good area for solar panels to be set up and mounted. but in general from March you can come off grid or off generator in the UK until  late October.

if your off grid the standing charge of grid power should cost the same or less to power the generator over the required time.

Cons:
Requires some wiring that can be confusing.

Class - lesser Modified Circuit 
Original should remain intact without change, Grid is junctional at the ATS.
Earth bonding

Purpose:
The idea here is that the solar is a standalone unit, inverter and battery provided in the kits as well as the solar panels. You would  remove the  circuit wiring in the CU and place these in the ATS output -  we have moved to DIN mounted ATS as this means that the wiring moves within the CU rather than having to pull out wires and bridge.
The solar power is provided from the inverter and if the battery and solar do not provide power the ATS will change to grid supply.

Partial Solar installation. Ideal to run lights or lower power sockets ( depending on inverter) or outbuilding /workshop

Difficulties
Earth bonding - 
Location of the solar array, battery and inverter to the CU. Will need to be housed.
House wiring may not reach across the CU to ats.

Cost effective?

3kw/5.1kWh/1.27kwp £1,700
5Kwh@0.29= £1.45 (£529 PA)
= 3.2 years ROI

We will offer a Recycle option to make this more cost effective,  Circ £1,300 (ROI 2.4 years)

Talk about option and issues here!