One huge factor in electrical heat, is if your utility has a TOU (time of use) rate. Mine doesn't, but I'm told many areas do, and that is custom made for a radiant floor heat install. Heat the concrete slab from whenever the much lower rates kick in, and shut it down before they end, using a simple timer. Coast thru the day time. One thing about electrical boilers, as compared to nat gas or propane, there is zero heat loss up the stack, because there isn't one.
When I built my current plane, the RANS S-7S, I framed in a 20' by 10' insulated room inside my un-insulated pole barn, and poured a slab with rad heat tubing over foam insulation. It was my paint booth, and I'd pre heat it to 75 degrees air temp using a 1 KW electric boiler, start painting, and stop when the temps dropped to 60 or so. I had to vary my technique with the spray gun as the temp dropped, but it at least had zero chance of blowing up. Turned out, by the time the temp dropped, I was ready to quit spraying anyway, had got done what was needed, other than the advance notice needed to get it up to temp at first (several hours) it wasn't a problem. Of course, it was winter time, so my cold filtered intake air was a big factor. I thought of running a temporary 24" duct over to the heated shop, 18' away, so at least the intake air would be 60'ish, but got done before I got around to it. Spraying Poly-Tone, which is pretty forgiving, it came out pretty good.