Hi Grassman,
We booked a week on the Mon & Brec two years ago - Easter time - hiring an all-electric boat from castle Narrowboats at Gilwern. It was a 4 berth cruiser, fitted with a former milk float engine and realistically limited to 2.5mi/h cruising speed. The dredged depth and the fact that the entire canal can be cruised well within a week meant that this was a suitable speed.
The advice, from memory, from the hire base was to to moor up at a charging point every night to recharge but we could get away with 2 day's worth of cruising at a pinch. As it happened, the places we would have moored at anyway on the way up - Llangynidr, Tal-y-Bont and Brecon - had dedicated and well-signed mooring/charging points. This meant that we were guaranteed a mooring. Similarly, we would have chosen to moor at Llanfoist and Pontypool on the southern section anyway.
Once we'd got used to the quiet, electric cruising is no different to diesel cruising and the M & B is well worth the visit as an interesting canal to do.
We'd happily do it all again once we've fully retired.
JCO