It does depend on what price IFN gets for the electricity and...

It does depend on what price IFN gets for the electricity and LGCs.
So, concentrating on FY19 I will take a stab at estimating that...

From the FY19 interim results:
" Electricity: The market remains in backwardation. Securing contracts which balance price against the value of contract tenor deliversrevenue stability
 Firming: The importance of firming increases in line with Infigen’s increasing number of C&I contracts
 LGCs:• Forward markets expect over-supply to drive down price. The rate at which this will occur is unknown. Infigen’s contracted sales arean important mitigant against a declining price• Commencement of operations at the Sydney Desalination Plant will increase LGC sales, but the trajectory is uncertain as it dependson the ramp up and actual electricity use
 Overall: The bundled price for electricity and clean products (LGCs or otherwise) is expected to remain strong given the need for newclean reliable generation"
and
"As CCGT requires a price of $90-100 MWhto be financially viable, Infigen believes that this willbe the new benchmark Electricity Price"

" Re-confirm $125 – $130 MWh for FY19 in respect of production sold from Infigen owned generation assets
 Price variation may occur based not only on production volumes, but production timing, geographic location ofproduction, spot and DWA prices and LGC spot prices"

I then make some outlandish assumptions to see where the EBITDA might end up for FY 19.
Last year's production sold was 1480GWh. If we assume the 23% increase from my guesstimate above to give $1820.4 GWh and $125-$130/ MWh that would make ~$227.5m -$237m sales estimate. The average price for H1 FY19 was $136.7 / MWh. That price that would put sales at $248.8m.

Costs have varied in the previous 6 months and with guesses based on the half year presentation they might be in the order of $69m.
The bear case then would be $158.5m EBITDA which would be 6.3% increase on FY18.
The SP just after the FY18 results were released was about 65c.

Looking past FY19 the battery will add a few more percent of production through firming and efficiency but average price will drop somewhat although not as much as FY21 due to high percentage of LGC contracts being in effect in FY20. Also Sydney Desalination plant operation may have a positive effect there as well. So maybe $118-$120 / MWh average and a slight increase in production sold to say 1900GWh would leave the FY20 EBITDA about the same as FY19.

Make what you will of that, DYOR and feel free to check my maths but IMHO IFN is solid for another couple of years at least despite the current energy policy.