To all those with questions on radiant floor operating cost I want to share my experience as any good info with details on this was hard to find when I was debating on in floor heat. Using 80 gallon electric HWT. 1200’ of ½ pex tubing divided in 4 300’ zones.
Backgound,
This is a copy past from a thread last year.
“I had a hard time getting cost info on these systems with all the information, so here is my first months heating with my specs. 30’x 40’ 1200sqft 3 bay garage with 3- 9’x8’ overhead doors, 1-3’x7’ ,man door, 3-3’x4’ windows A 8’x4’x 8’ tall kick out on the back where the HWT, and compressor are Isolated from the main area. Walls are insulated with 2-layers of what looked like old R13 Insulation that I bought used on craigslist, the ceiling is R19 in the 40’x 8’center area with OSB spaced off the 2x4 trusses for storage, with the sides done with 2 layers of R19, top layer un-faced to get R38. I have the foil backed bubble wrapped insulation under the 4” slab and wrapped up the sides of the slab also. This may be my down fall, but it is too late to change now. I live in SE OHIO, and AEP supplies the electric.
The temp was set at 65 to start, and then I turned it down to 55 after a week or so, to help cut some cost, and because to work in a sweatshirt I don’t need any more than 55. It is very comfortable; if you are moving a lot you may even loose the sweatshirt.
My last meter cycle was from 11-16-09 to 12-18-09, the garage has its own meter. I started heating on 11-29-09. For the month I used 1242 KWH, 1195 KWH were when the heat was on. My normal KWH usage a month prior to heating were around 110 KWH a month. The system ran for about a day and a half straight, but I did fill with hot water from the HWT in the house. With the extra amount of energy used my usage rate went down, and my bill was $105 from my normal bill of $25-30 per month. My price per KWH is $.07 (I count everything except the meter charge into the price per KWH) my meter charger is $13.17 FYI.
With my heat loss calcs between 12,500 to 16,000 btu/h this is about what I expected. I plan on adding some more insulation around the edges of the slab just for fun. I will keep everyone updated on how everything works, but I am still thrilled with the system.”
Year later update. 2010-2011.
See above post for garage specs. I did add 6” strips of 2” foam all around the perimeter except for at the garage doors. Tried heat at 50 so see how cold it would feel. It is perfectly conformable to work in a sweat shirt. Temp will stay at 50.
My bill for 11-16-10 to 12-20-10 I used 1153 KWs, and had a bill of 108. $13 meter fee, and the rest I figure as $per KW, and it was about 8 cent per KW.
My main heating element in the HWT went bad so I replaced both with 5500 Watt elements from 4500 Watts. I saw no difference in $, but hope it helped the recovery time, but I don’t stand there and watch that close.
My bill for 12-20-10 to 1-21-11 I used 1439 KW $133.
It was pretty cold in Dec here so I am very happy with this. My bill over the summer with welder, compressor, HWT, and other normal things was 30-35 a month, so Heating cost me $78 in Dec. and $103 in jan.
When compared to my house heating costs I cant complain at all considering the garage is about as big as the house! If I had any natural gas on site I would have used that to heat the water, but all is electric and the HWT was free so why not. The system has never had a problem of "keeping up" with the heating even when it was -10 last week, it is always within 2 deg of set temp.
I have not tried to optomise the system, but I have a mixing valve before the pump to recirculated water coming out of the floor with hot water to ease the burdon on the HWT. Water into the floor at about 90deg. out at 60. I also have the valve on the positive side of the pump closed a bit to slow down the water flow. I may try adjusting these and see if I notice any difference. Just for fun I read the meter everyday on my way to work and compare the average temp of the day so I can see if tuning makes any difference.
I hope this helps someone, I know I would have enjoyed something like this when I was debating heating methods.
Backgound,
This is a copy past from a thread last year.
“I had a hard time getting cost info on these systems with all the information, so here is my first months heating with my specs. 30’x 40’ 1200sqft 3 bay garage with 3- 9’x8’ overhead doors, 1-3’x7’ ,man door, 3-3’x4’ windows A 8’x4’x 8’ tall kick out on the back where the HWT, and compressor are Isolated from the main area. Walls are insulated with 2-layers of what looked like old R13 Insulation that I bought used on craigslist, the ceiling is R19 in the 40’x 8’center area with OSB spaced off the 2x4 trusses for storage, with the sides done with 2 layers of R19, top layer un-faced to get R38. I have the foil backed bubble wrapped insulation under the 4” slab and wrapped up the sides of the slab also. This may be my down fall, but it is too late to change now. I live in SE OHIO, and AEP supplies the electric.
The temp was set at 65 to start, and then I turned it down to 55 after a week or so, to help cut some cost, and because to work in a sweatshirt I don’t need any more than 55. It is very comfortable; if you are moving a lot you may even loose the sweatshirt.
My last meter cycle was from 11-16-09 to 12-18-09, the garage has its own meter. I started heating on 11-29-09. For the month I used 1242 KWH, 1195 KWH were when the heat was on. My normal KWH usage a month prior to heating were around 110 KWH a month. The system ran for about a day and a half straight, but I did fill with hot water from the HWT in the house. With the extra amount of energy used my usage rate went down, and my bill was $105 from my normal bill of $25-30 per month. My price per KWH is $.07 (I count everything except the meter charge into the price per KWH) my meter charger is $13.17 FYI.
With my heat loss calcs between 12,500 to 16,000 btu/h this is about what I expected. I plan on adding some more insulation around the edges of the slab just for fun. I will keep everyone updated on how everything works, but I am still thrilled with the system.”
Year later update. 2010-2011.
See above post for garage specs. I did add 6” strips of 2” foam all around the perimeter except for at the garage doors. Tried heat at 50 so see how cold it would feel. It is perfectly conformable to work in a sweat shirt. Temp will stay at 50.
My bill for 11-16-10 to 12-20-10 I used 1153 KWs, and had a bill of 108. $13 meter fee, and the rest I figure as $per KW, and it was about 8 cent per KW.
My main heating element in the HWT went bad so I replaced both with 5500 Watt elements from 4500 Watts. I saw no difference in $, but hope it helped the recovery time, but I don’t stand there and watch that close.
My bill for 12-20-10 to 1-21-11 I used 1439 KW $133.
It was pretty cold in Dec here so I am very happy with this. My bill over the summer with welder, compressor, HWT, and other normal things was 30-35 a month, so Heating cost me $78 in Dec. and $103 in jan.
When compared to my house heating costs I cant complain at all considering the garage is about as big as the house! If I had any natural gas on site I would have used that to heat the water, but all is electric and the HWT was free so why not. The system has never had a problem of "keeping up" with the heating even when it was -10 last week, it is always within 2 deg of set temp.
I have not tried to optomise the system, but I have a mixing valve before the pump to recirculated water coming out of the floor with hot water to ease the burdon on the HWT. Water into the floor at about 90deg. out at 60. I also have the valve on the positive side of the pump closed a bit to slow down the water flow. I may try adjusting these and see if I notice any difference. Just for fun I read the meter everyday on my way to work and compare the average temp of the day so I can see if tuning makes any difference.
I hope this helps someone, I know I would have enjoyed something like this when I was debating heating methods.
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