rberq wrote:OK, measurement begins today. I installed a meter at the inlet to my Superstore tank, so I can measure how much domestic hot water I use per month. I know from several years of records that I average 22 gallons of oil per month to make hot water. Also I just filled the oil tank a week ago, so beginning metering of water and beginning drawdown of the oil tank coincide. So in a few months I should have pretty accurate figures as to how many gallons of hot water a gallon of oil will make. Then it will be very easy to calculate the savings (or not) of switching to an electric water heater.
One year later. The meter shows about 1,000 gallons of hot water per month (below average because it's just two people). Oil usage dropped significantly from the 22 gallons per month when I reduced the boiler high-limit. Without burdening you with the calculations, the cold-start oil boiler with Superstor was running between 25 and 30 per cent efficient. That is, one gallon of oil = 140,000 BTU, but only 35,000 to 40,000 BTU delivered to the water. Even with our high electric rates, I estimate savings of $25 to $30 per month for an electric heater, which has now been installed and should pay for itself in less than two years.