I Think they are 1500 watts?
Not sure if I did the math correctly but .. They are Big units and Really put out the heat .. "If" you run them constantly! 8(
If they're 12.5 amps, your math looks right to me.
Here in MN I haven't turned on my furnace yet this heating season (except for a 10 minute test a month ago). I've been using solar heating from a setup I designed and built and a small 1500 watt electric heater. That and the heat the computer and TV and cat and so forth throw off.