Cost to get hot water from tankless coil in boiler

[ITD]

Originally Posted by SailinAway

This calculator might help: https://www.efficiencymaine.com/at-h...st-comparison/

I entered values for 5 gallons a day, price of oil $5.80 a gallon, and cost of electricity $.1658 per kwH. The result was $74 a year for a tankless coil and $55 a year for the electric water heater.

That doesn't seem right. I think both figures are too low, otherwise I would not have turned off the hot water tank. The calculator doesn't include the size of the water tank. In any case, "oil boiler with tankless coil" is the most expensive on the bar chart.

I think heating water with oil is cheaper than using electricity. I looked at the link you provided, it looks pretty much like I'd expect. I think the default efficiency for oil list there is too low. I changed it to .85, unless you have a really old boiler yours is probably closer to 85% than 60 % too.

For 5 gallons a day, I got $65 for oil and $86 for electric.

The thing about using your boiler is that the boiler temperature needs to be kept hot enough to give hot water in a reasonable time. This uses additional oil versus what it would take to just heat the 5 gallons a day. I'm wondering if your link takes this into account. I actually think it may based on my original guess of 1 gallon a day.

"In the noise" means that if you could instantly heat 5 gallons of water with oil and not have to keep the boiler hot, it would probably take a gallon of oil a week rather than every day.

But in the end these are just estimates and the difference in cost negligible between oil and electric. It would take far too long to break even on the cost of changing over to justify it. I would just turn the electric heater back on and forget about it until the tank fails.