I use a wood range to heat my cape cod house (21'x32'), cook and heat my water.

I need a back-up heating to satisfy the insurance and to keep the plumbing from freezing for the unexpected case.

I did not use any back-up heat in the past 10 years so my requirements are minimal.

Few years ago I installed a 10000 Btus output (3kW) second-hand propane space heater with balanced flue and piezo start hooked on a couple of 20 lbs propane cylinders with an automatic switch.

It works but needs checking, is slowly rusting away, makes a hole in the wall and has never been used.

I am thinking of replacing it with a few electric baseboard heaters.

I have a 100A electrical service and won't change that. If the baseboard heaters kick in they will be the only load beside the small fridge and freezer I have in the house. I cook on propane in the summer.

What size baseboard heaters should I use and how many?