Hi was just talking to a electrical inspector and as stated above 80% is right but a 70amp breaker may peek at 2000 watts with out tripping that would be a instantaneous Peck and a return to the 80% load. PB is also right about the wire gage. as far as just swapping out the panel that would all depend on the gage of the feed line into the house. if the line to the house is older it will most likely have to be replaced, have an electrician look at it.
Shell buzzy was on the radio last week and they are changing thing here in BC in the future. where as if a home owner dose any electrical work it has to be inspected or your insurance becomes void. I don't know how accurate what he was saying was as he was kind of being very general about it all. I am thinking it has more to do with the individual circuit that the person installs including electrical outlets. This because there has been instances where a home owner ran the neutral through the breaker and then the hot side became the neutral and houses have burnt down because of it. I've heard about this a couple of times. I have seem it once while a house I was thinking of buying was being inspected. that was a deal breaker right there and then as you have no idea what else was done incorrectly in the house or where it was gizmoed to gather.
I'd just rather a person get the profesinals to look into it.

As far as having a panel upgraded to 100AMP as i said my mom has to get it done but she also has to move her mast she told me they wanted some thing like 3000 to 3800. You get it all back in resale value as a upgraded panel is some thing a new owner does not want to pay for in most instances. On my moms line BC Hydro had already changed the line to the house so it is ready to move over to a new panel and mast, the new mast will be closer to the pole than the old panel. so I don't know if the charge includes that cable or not I am asumming that it does not.

Bill