Hi lemur,
I just joined and looks like I was lucky enough to find a question I know quite a bit about. I'm an electrical engineer in power transmission (Very High Voltage Power) , which is technically not the industry that deals with home PV installations but I know enough about the general concepts. As the other poster said, the power on your grid is in AC. This is basically because it's easier and more efficient to transform AC voltages. But to specifically answer your question, the power your house creates won't be going very far anyway. It will most likely just be powering next door's plasma tv. From the point of view of distributers (Lower Voltage Utilities), home PV solar is seen as just reducing the combined load of say your street or neighbourhood. This is actually in a lot of ways the purpose of these home PV initiatives from the government. They reduce peak load at critical times (PVs create more power on hot days when you are using your air con). Since networks are designed for peak loads and not average loads, this allows governments/utilities to delay major improvements to the network. But it is a very expensive quick fix and i digress.
In AC, current flows back and forwards equally (50 times a second in my country) so the electrons realistically go nowhere. So you need to picture power "flowing" through the lines rather than current (like you would with a DC circuit). It's true, there are physical limitations but you don't really need much current to allow power to flow through the transformers you wrote about. They are designed to operate under low currents. The only restriction is the magnetising current of the transformer, not really the voltage (even though voltage and current are essentially two sides to the same coin). This is typically very small and I think I'm going into too much detail anyway
So, the only thing the inverter needs to do is to create an AC voltage from the DC voltage from your PV cells. This AC voltage need to be at the normal level (my country has 240V) at the same frequency and phase as the network. Once it has done that, the power that your PV setup creates can flow into the network (the current will vary depending on the amount of power) and into your neighbour's tv.
I think i answered your question but if you want to know more, feel free to ask questions. I can make the answer as complicated as you want
