I hesitate to respond with my own, personal IGH experiences because as both
@neptronix and
@amberwolf already wrote, most of the established (and reasonably priced) IGH hubs aren't rated for the full BBSHD grunt, if rated at all.
But ... this is a forum for real-world experiences and/or opinions and all that - so here goes some of my own.
My initial, as an owner of a small fleet of IGH e-bikes, thought is that, if you're willing to be particularly cautious when up-shifting an e-overpowered IGH hub (such as the Shimano Nexus 3-speed, the Shimano Nexus/Alfine 8-speeds, and the Rohloff 14-speed - all of which I own), and throw in/on a shift sensor for insurance (because sh$t happens), then in my personal experience these hubs can hold up to the power abuse. What kind of power (motors / wattage)? My bikes have open-source BBS02 (max 28 amps), CYC (max 38 mps), Luna V2 controller BBSHD (max 60 amps) motors, and I've not wrecked or even damaged the IGH hubs listed above. Early on, I did pull apart a few chains, but upping the chain quality and/or going 1/8 seemed to cure the issue. I've also softened the initial ramp-up power (where possible) within the motor settings.
AFAIK, the Rohloff is the only IGH with built-in over-torque protection (via nylon sheer pins).
Also AFAIK, all recent IGH designs with more than 5 speed are two-stage (primary ratio section with a high/low), and may not shift correctly under pedal/motor load. A shift sensor helps - on a dual-cable Rohloff, on the upshift cable.
Dan Burkhart on youtube has several IGH related videos that may give you an idea on the current IGH construction qualities (or lack of). For example, IMHO, the Sturmey-Archer (now Sun Race) machining/metallurgy looks pretty bad, though some seem to have e-powered success with the hub locked in second-gear 3-speeds. One needs to remember how ancient the SA hubs designs are, after all, as well as the design target rider/usage. I'd avoid the 5-speed SA hubs in particular - just asked Luna Cycle.
There are several new up-and-comer IGH designs out there, like the 3x3 and fairly established two Kindernay hubs. But, for now, I'm sticking with either the low-cost Alfine-8 that has a reasonable gear range and parts availability, or splurge for the tried and true (and easy to cope with chain line) Rohloff. I use the older SG-S501 Alfine-8 series, but the newer SG-S7001-8 ones are probably ok (be sure to get the
correct shifter) - both are cartridge designs, meaning that there' are "guts packs" available for both, and that's the standard repair path, I believe. The Shimano 8-speed hubs have somewhat irregular gear steps (and gear efficiencies), but I've gotten used to them - versus, the very evenly stepped Rohloff.
At one time, I did have a bike set up with the Shimano Nexus 3-speed, and while it operated fine the ratio range was too narrow for the particular terrain the bike was run on.
I briefly considered the new Shimano 5-speed IGH, but it's overall gearing range either requires small wheels or a smaller (than I can manage) front chainring. For some reason, on this hub, Shimano set the low gear as the 1:1 ratio gear.
Here are some
examples of my builds, most of which have IGH hubs (and strong rear triangles and adjustable dropouts to deal with the IGH twisting force). My terrain is hilly, and the total rolling weight was at one time 400lbs - thankfully now down around ~290lbs. I ride mostly errands, in traffic, where speed helps.
P.S. I'm responding to the initial topic question, but as other responses suggest, for your situation a quality hub motor seems a better fit. I've got a beach / flat terrain
hub motor build underway - my first stab.
