You can use my spreadsheet linked at the bottom. If you
don't trust my spreadsheet you can track down Dr. Alfred Körblein's model (in
German) and use that. I haven't looked at his model in over a year so I don't
know how he's treating self-consumption these days or even if he's kept it
updated. I recently saw a comment of his on PV Magazine and he thinks the new
FiT rates in Germany are fine. That tells me our models are kicking out similar
results.
To use the model go to the Input Parameters page and enter
in the current system prices, O&M, kWh/kWp, interest rates, discount rate,
etc in the gray fields. The input data needs to be in per KWp increments. You
have to be careful but it's hopefully intuitive - if not I'll write up some more in depth
instructions. The default values are all referenced and are specifically set to
model the current situation in Germany. The results pop up in the Orange box on the right hand side.
The most under-appreciated parameter is the self-consumption
rate. You can vary that from 30% to 50% and see what I mean.
We often hear that FiTs are set to deliver an 8% return on
investment. You can play with the model yourself to see how system prices and
FiT rates conspire to deliver X% rate of return or Y net present value based on
the inputs.
When I play with the model it's clear to me the FiT rates
for the sub-10 kW tranche can come down significantly. The FiT rate is actually
a secondary concern - you could set it at 10 cent/kWh and still clear the economic hurdle tests. The FiT used to be about making money - now it's about
saving money. A counter argument here is that retail rates may come down in the
future and this would impact the profitability of your system. That's
absolutely true but there's a hedged risk here. If electricity prices go up you
save money with PV. If they go down you lose money on the PV investment but you
save money on utility bills. The showstopper would be if electricity rates
dropped sharply over a short time period but that seems unlikely to me.
I'm guesstimating that prices for small and medium sized systems
come down to 1500 Euro/kWp in the near term and stabilize around there. If
system prices get down to this level your production costs (the LCOE) are at 10
ct/kWh. This gives you a lot of room to chop the FiT rates. As mentioned previously, things very much
depend on your self-consumption profile.
An additional thought here is that the FiT shouldn't
necessarily be based on installed kWs. Another way to go about it would be to
base the rate on total backfeed. This structure would encourage a balance between economies of
scale and overall system integration (generation matched to load) at the same
time. I like that. We shouldn't unnecessarily punish a roof that's good for 12
kW when a 10 kW system may actually back feed more. Make the top FiT tranche
apply to the first 10 MWh of backfeed per year. The next tranche would apply
to the next 90 MWh and so on.
It's my belief that the BSW, DECC, GEA etc should be putting out a standardized model
like this themselves - a better cleaner model of course. Things need to be transparent. The Government should be
using the exact same model to set FiT rates so we're all on the same page and
everybody is held accountable. People will still complain but at least we'll be
clearer on what's being debated.
Disclaimer: I think my model works but some bugs and brain
farts may have slipped in/out.
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