Some further clarification…
I interpret what you’ve written that the old heating system was an oil fired boiler that used pumps to circulate hot water with an loop that indirectly heated a domestic hot water tank.
*The old system was an oil fired boiler with a chimney that used pumps to circulate hot water to baseboard, and a coil to provide domestic hot water.
*The new system is a gas fired burner, with a direct vent instead of a chimney, it's a "high efficiency" traditional cast iron, and since gas doesn't get as hot as oil, it has a separate indirect 50 gallon hot water tank. (The boiler heats the water and it allegedly keeps the water at temp for two days).
So the only change to the new system is just a change from oil to gas, plus the new higher efficiency boiler uses a small fan to exhaust the burner combustion gas. Is that correct?
Also, there have been no other changes to the house that would account for increased electricity usage. Is that correct?
*That is correct. The only other change is to lighting, everything was changed to LED low watt lighting. so that wouldn't do it. anyway, those lights are off 99% of the time.
Has there been a change to the heat emitters (radiators, etc.)? Are the same areas of the house being heated using the same emitters?
*One level is now hydronic radiant heat, whereas before it was baseboard. Other level is still baseboard. I was told this would use LESS energy. Biggest change is pipes went from copper to pex.
I’m sure that you would have mentioned this if it was not the case, but can we assume that the indoor temperature has been constant before and after the heating system change?
Has the high monthly electrical usage gone on over a number of months so that you can eliminate any reno related electricity usage, such as someone leaving windows open for a few weeks to air out fumes?
*Yes. Temperature constant. Actually, its a few degrees lower now. (not much, just 4).
Can you give us an idea about the climate where you live. Your comment about the 200 kWh consistent monthly usage seems odd for a climate where it gets cold in the winter.
Avg 200kwh in the winter. +/_ like 10-20kwh. East coast/metro New York.