Running the numbers III - on-demand hot water heater
OK, I'm sold on these units. In situations like ours, they ROCK.
We knew we were kicking ass on fuel conservation because, duh, we'd been able to go an extra several months between fillups on the propane. Summer's usually a low-consumption time, because we are tapping the tank only for cooking and the hot water heater. Since between myself and the gas company we have a record of the pressure and temperature at regular intervals, a little work was all it took to get me a fairly decent estimate of the gas consumption from spring shortly before we turned off the house furnace, to today when we had the propane topped off for winter.
In 6-7 months, we used about 50 gallons of propane, at a cost of about $105, all for cooking and hot water heating except for the first couple of weeks which would have still had some house-furnace heating in there.
That makes our annual gas cost for those functions somewhere in the 100-125 gallon range; I'm bumping up a bit to adjust for rounding issues and that the heater will have to work a bit harder in winter when the incoming water temperature is about 10F cooler. My showers run a bit longer :) Plus in winter I tend to do more long-simmer-on-the-stove stews.
Still, 125 gallons/year for the hot water heater AND cooking is a bargain. It's a bit more than half of the annual estimated energy cost of the hot water heater alone (200 gallons for typical house/family that it's sized for). We're not only using far less propane than we expected for our hot water heating, we're getting the cooking for free!
And this is icing on top of the 2009 tax credit we received for replacing with a super-high-efficiency-unit. The $646 tax credit alone brought the final installed price down to below what it would have been for standard 40-gallon tank, non-ultra-high-efficiency unit.
Also, to be fair, the new stove has to get some credit, too. Last year's kitchen remodel included a new gas stove that had fancy burners and a low-simmer-burner and it's probably as much a step above the old stove in efficiency as the hot water heater is. Unfortunately, I don't know how to accurately estimate the stove's gas consumption. I've got the figures for BTUs per gallon of fuel, and burner BTU, but I don't do things like run a 12,000 BTU burner on full for an hour.
Previous run-the-numbers for this item for 2009 here: http://hawklady.livejournal.com/223230.html
We knew we were kicking ass on fuel conservation because, duh, we'd been able to go an extra several months between fillups on the propane. Summer's usually a low-consumption time, because we are tapping the tank only for cooking and the hot water heater. Since between myself and the gas company we have a record of the pressure and temperature at regular intervals, a little work was all it took to get me a fairly decent estimate of the gas consumption from spring shortly before we turned off the house furnace, to today when we had the propane topped off for winter.
In 6-7 months, we used about 50 gallons of propane, at a cost of about $105, all for cooking and hot water heating except for the first couple of weeks which would have still had some house-furnace heating in there.
That makes our annual gas cost for those functions somewhere in the 100-125 gallon range; I'm bumping up a bit to adjust for rounding issues and that the heater will have to work a bit harder in winter when the incoming water temperature is about 10F cooler. My showers run a bit longer :) Plus in winter I tend to do more long-simmer-on-the-stove stews.
Still, 125 gallons/year for the hot water heater AND cooking is a bargain. It's a bit more than half of the annual estimated energy cost of the hot water heater alone (200 gallons for typical house/family that it's sized for). We're not only using far less propane than we expected for our hot water heating, we're getting the cooking for free!
And this is icing on top of the 2009 tax credit we received for replacing with a super-high-efficiency-unit. The $646 tax credit alone brought the final installed price down to below what it would have been for standard 40-gallon tank, non-ultra-high-efficiency unit.
Also, to be fair, the new stove has to get some credit, too. Last year's kitchen remodel included a new gas stove that had fancy burners and a low-simmer-burner and it's probably as much a step above the old stove in efficiency as the hot water heater is. Unfortunately, I don't know how to accurately estimate the stove's gas consumption. I've got the figures for BTUs per gallon of fuel, and burner BTU, but I don't do things like run a 12,000 BTU burner on full for an hour.
Previous run-the-numbers for this item for 2009 here: http://hawklady.livejournal.com/223230.html