I have a cold start indirect and I still figured I'm using .74 gal/day. Of course, any of my numbers could be off.
I've been taking daily readings off the electric meter.
35508 was a good thread: https://www.hearth.com/talk/threads/cost-to-heat-dhw-with-oil-tankless-update-1-month-later.35508/
It'd sure be nice to have a gasifier with storage.![]()
I think I did this sometime ago but here are my calculations. Correct me if any assumptions/math is wrong. I am not seing the big savings with an electric water heater at oil's current price. Here goes:
Assume 4773 KWH yearly use for hot water as per the DOE spec. At 16.4 cents/kwh, (my rate) that is $782.00/year. For oil, 4773 kwh = 16286153 btu's. Assume #2 oil is 138,500 but/gallon. At 80% efficient (mine is higher), I get 110,800 useable btu's/gallon. 16286153 btu's/110,800 btu's gallon = 146.98 gallons oil/year. At (my rate) $3.64 gallon, that is $535.00/year, $247.00 (68 cents/day) less than electric. To be equal, oil would have to be $5.32/gallon. Another angle would be that if your oil appliance was only 55% efficient, the hot water bills would be the same.
We assumed both heaters have the same standby losses but the boiler has some. I figure a 20 gallon boiler going from 180 deg to 100 deg once a day would lose about 12,480 btu and cost maybe 40 cents/day. Many boilers have burner dampers that close to prevent stack loss as does mine. Incidentily, I have a power venter so no chimney losses. You also have operating cost for an oil boiler which, ironically, electricity is needed. I am not sure what the consumption is but I will look into it. Maintenance/installation cost are a consideration. The only way you can compare is life cycle cost between them.
It would seem at this hot water useage example, it is a wash between the cost of oil or electric in this situation. I do have a 100 tube evac solar array for domestic water so I can't really use a real world example.
That's shorter than I thought it'd be.Just got my Geospring up and running. Now I can take my time with the vigas install and not have to worry about getting my DHW from oil!
How do you heat your DHW now and what is your actual annual cost? Depending on the setup, I think oil DHW heating would be lucky to be 50% efficient in some cases.
I'm early in my evaulation, but I know that over the last 6 years or so, I was using on average about 150 gallons (Canadian) of oil for heating DHW in the off-heating season (about 6 months). My last electric bill, for which I had my electric tank up & running for close to half of the billing period (one month out of two), was about $20 more. I had a tankless coil oil boiler that had to stay hot (140-150) all the time. I admit my math is pretty fuzzy so far - I'm expecting the next electric bill will show more of an increase. But I also have yet to add insulation to the electric water tank, which is also in my plans.
We use essential cookies to make this site work, and optional cookies to enhance your experience.