ECN Forum Forums General Topics of the Trade General Discussion Area Generator Cable Sizing

How does everybody here size the cable for home standby generators? Here's the situation... A customer called me for a Generac generator. He has already installed #3 TECK cable (along with the control cable) from where the generator will sit, to the house. I believe that the OESC, CEC and NEC all agree that this cable is rated for 100 amps. If it's a continuous load, you're not supposed to exceed 80% or 80 amps. The customer wants the biggest generator he can get on this cable.
Generac says:
16kW - Max rated load of 66.6A, protected by a 70A breaker
20kW - Max rated load of 83.3A, protected by a 100A breaker
22kW - Max rated load of 91.7A, protected by a 100A breaker
Which generator would you choose?
Thanks

Unless it's a continuous rated generator (unlikely in this size/price range), it's not capable of supplying continuous service; standby rated generators are only capable of 70% average load for 200 hours/year. If it has an integrated breaker, you don't need to oversize the conductors; that breaker's probably only 80% rated anyway. He should be good up to 24kVA standby on a 100A cable. Is that 22kW really 100% rated as the Amps suggest, or is that some sort of fine-print marketing?

Unless the sole load on the generator is electric heat...and it's running 24/7 none of the typical residential installations are a continuous load.
I don't see a problem using the pre-installed cable at 100% of its rating.
Keep in mind that the ratings of the generators assume a completely balanced load.

Going for the 22 KW unit may be the best choice depending on the $$$ differences over the 20 KW.

Based on the permits I process, 22 KW units are in the majority, followed by 20s, and 16s are few.

Common is a 200 ATS, 22 KW Gen, 100 gen, 200 utility, to the existing 200 amp panel (w/neutrals/grounds separated) and load shed for the HVACs, etc.

Thanks for the responses.
22kW it is then. It really is helpful to be able to bounce things off of others.
Cheers