Generating Electricity with the Prius

I know this has been discussed before, but I'd like some input on calculating energy efficiency and if the Prius could serve as a generator or if e.g. a regular petrol generator is FAR more efficiënt. I lack the insight on how to calculate this.
How much does each kWh in electricity produced by the PriusGen2 cost including all (in)efficiencies?


What comes next is somewhat offtopic, but explains why I am asking:

My solarpanels are close to equilibrium (?) or exceed my annual electricity usage (~4000kWh, we use gas for cooking, heating and warm water, but since this is causing small earthquakes in our country where it is won, we (as a country) want to reduce this usage fast and the price is rising accordingly). I still have some 1.4kWp in panels not hooked up, so could produce 1000kW/y extra.
My energymeter runs backwards, so each kWh costs me 25ct and each kWh put back earns me 25ct as long as I don't put back more than I use (per year). This (legal) possibility of using the grid as a buffer will (unfortunately!!!) stop in 2020.
From then on each kWh will cost 25ct, every kWh given back into the grid will earn me 7ct. So it is essential to use ALL produced electricity myself ('earns' or 'saves' me 18ct compared to putting it back into the grid and taking it out again later).
I can add a boiler (80-200liter watertank with heater), a Telsa powerwall (or equivalent), an electric car, etc in the summer and obviously some electronics to switch those ON those when I am a net producer of energy. But in the winter I will still need the grid. Or a generator/Prius.
The gridconnection costst a lot of money in fixed costs, regardless of how much kWh's you use: this was increased greatly a decade ago when people started using solarpanels a lot more: even if you supply all your energy through your solarpanels (so seen over a year your demand and supply even out), you are still paying through your nose for being connected to the grid (those companies aren't dumb and saw this coming a mile away, although their reasoning behind this was obviously 'for the clients good'...)
Easiest would be to disconnect the gridconnection, buy a Tesla powerwall and have a 1kW extension cord to the neighbours, but that isn't a viable solution... (Even though he does have a single large serverrack (=his company), so even if I have a surplus, he would use much of it himself).

 

It will be here too after 2020.
They are failing the old Ferraris meters in a high pace so people have to accept a digital meter* with separate use/produce counters. (Meters are owned by the electricity company here in the Netherlands).
The fact that huge numbers are now failing spottests since the government and electricity companies decided we had to go to digital meters is suspect according to some. The fact little to no info on the testing method and sample sizes is anywhere to be found online, feeds this distrust. But that is another matter.

Great project in your sig


* the digital meter is 'sold' here as a "smart meter" because it automatically sends your usage data to the electricity company (and if you give third parties access to this data you can e.g. see almost real time usage and solar-production data on apps).
Most solar panel users obviously refer to it as a dumb meter as it cannot subtract produced energy automatically. With the new digital meters, it has happened that electricity companies ADDED the produced solar power to the used energy so people ended up paying for the energy they produced themselves...

 

That gives me a very nice estimate. And it is low enough to warrant some more in depth calculations. Thanks!