Stupid me tried to out smart my heating system. I have two boilers hooked up to my radiators; a natual gas boiler and a coal stoker (efm). I figured that it might be cheaper to heat with natural gas in November while the days flipped between warm and cold. Gas is on-demand and coal just keeps running. I switched over to coal on 11/23 (the day after thanks giving) because the forecast indicated consistent colder temperatures. I got my natural gas bill in yesterday, $96. Based on the billing statement, I was using the gas boiler for 10 days before I switched to coal. I went on weather.com to see the highs and lows for those 10 days. I figure there was 5.5 heating days with the avg temperature around 44 degrees. I surmised that if I had just heated with coal, I would've used between 1/8-1/4 ton. No more than $50 worth of coal. So it looks like a 2-1 savings btwn natural gas and coal.
Coal is King. Sorry for testing thee.