There are many threads on this forum that go into detail about this, based on calculations rather than guessing.
Based on my own calculations, I would say your guess is a little on the low side, but that is the subject of these other threads...
The math is quite simple really, let's start with the basic assumptions:
Fuel energy: 46MJ/kg
Maximum Fuel Flow: 100kg/h or 0.0278kg/s (As per the Tech Regs)
Estimated ICE efficiency:
Conservative: 38%
Likely: 40-43%
MGU-K Output
Sustainable MGU-K Power (continuous): 70kW (Brayton Cycle power from MGU-H)
Full Battery Power (as per Tech Regs): 120kW
Increased ICE Power from bypassing Turbine, and powering compressor from Battery via MGU-H: 15kW (Quali mode)
At 38% efficiency PU Power output is estimated as ICE + MGU-K Power:
ICE Power = Fuel Energy x Fuel Flow Rate x Efficiency = 46 x 0.0278 x 38% = 486kW (~650hp)
Total PU output in various modes (for 38% ICE Efficiency):
Sustainable Mode (+70kW from MGU-K): 556kW (or ~740hp)
Full Battery Mode (+120kW from MGU-K): 606kW (or ~810hp)
Quali Mode (+120kW from MGU-K and extra 10kW from ICE): 621kW (or ~825hp)
If we consider an ICE efficiency between 40-43% (which has been suggested), we get:
ICE Power: 510-550kW (680-730hp)
Total PU output in various modes:
Sustainable Mode (+70kW from MGU-K): 580-620kW (or 775-826hp)
Full Battery Mode (+120kW from MGU-K): 630-670kW (or 840-890hp)
Quali Mode (+120kW from MGU-K and extra 10kW from ICE):
645-685kW (or 860-915hp)
My math is rough, but it gives a crude approximation. Peak power will be between 10,500 and 11,000RPM, as the fuel flow rate increases to 10,500 and is then fixed at 100kg/h.
I will wait for GruntGuru to chime in and give you a more formal education...
In the mean time, try this:
http://www.f1technical.net/forum/viewto ... f=4&t=9259