generic snow melt operating cost question

[JesseN]

In an effort to determine the operating cost of a snow melt system I came up with the following using generic guidance:

For a 1000 sq ft slab which required 100 BTU/sq ft of heating to melt 1.5" of snow per hour, it would require 100,000 BTU/hr. Since 3413 BTU = 1 kWh, this would require 29.29 kWh of electricity. At a rate of $0.0472 per kWh, this would be $1.38 per hour of use if an electric heating source was used.

Seem somewhat close?

Any input on the 100 BTU/sq ft requirement?

 

[awdblazer]

that seems cheap for electricity
we have one of the cheapest rates at 6 cents an hour

 

[KinzeMech]

Your calculations are correct.

$.0472 / kWh is a very low cost, are you sure that is correct?

I don't know about the heat requirement for snow melt, but 100 BTU/sqft sounds low, too

 

[JesseN]

for winter rates (Oct. 1 thru May 31) it is as follows:
9.64 per kwh for first 100 kwh
8.34 per kwh for next 780 kwh
4.72 per kwh for the rest

We use over 3000 kwh every month so I just used the 4.72 for my numbers.

Summer is 10.48 per kwh which hopefully wouldn't ever apply for the snow melt system, ha ha.

 

[Angelfire]

I know nothing about snow melt systems but just thought I'd remind you to think about any efficiency losses when making your calculations.

 

[stingry]

In an effort to determine the operating cost of a snow melt system I came up with the following using generic guidance:

For a 1000 sq ft slab which required 100 BTU/sq ft of heating to melt 1.5" of snow per hour, it would require 100,000 BTU/hr. Since 3413 BTU = 1 kWh, this would require 29.29 kWh of electricity. At a rate of $0.0472 per kWh, this would be $1.38 per hour of use if an electric heating source was used.

Seem somewhat close?

Any input on the 100 BTU/sq ft requirement?[/QUOTE]

Hi Jesse
Where in NE are you? I'm near Scottsbluff. I ran your numbers thru a Radiantworks Pro program that I used to design the radiant floor in my shop. I don't know what type of a snowmelt system you are planning, either electric mat or electric heated liquid in tubing. Either way, the heat load should be similar. Using the design parameters of -8 def F, 9mph wind speed, 36" of snow/day(1.5"/hr) and 6729 deg days, is spit out a load of 230 BTU/hr/sq ft. Based on this, I would guess that you are low in your estimate.

Cheers
Steve

 

[Stuart in MN]

Tyco has some information on how to size snow melt systems on their website: http://www.tycothermalcontrols.com/usa/english/snow_melting/

 

[MoonRise]

Nice find on the Tyco website.

Their snow-melt cost calculator comes up with ~$500 for 1000 ft2 in Omaha, Nebraska at $0.08/kw-hr. The cost detail page then breaks it down as ~$400 in electricity and $100 in "maintenance" annually. 13,912 kw-hr estimated annually.

http://www.tycothermalcontrols.com/usa/english/snow_melting/designtools/calculators.aspx

And $0.04/kw-hr seems really low. Did you remember to factor in the 'delivery cost'? Electric utilities (around here) now split the cost of the electricity itself away from the 'delivery' cost of that electricty flowing though their wires (and switches and transformers and so on).

 

[tdkkart]

for winter rates (Oct. 1 thru May 31) it is as follows:
9.64 per kwh for first 100 kwh
8.34 per kwh for next 780 kwh
4.72 per kwh for the rest

We use over 3000 kwh every month so I just used the 4.72 for my numbers.

Summer is 10.48 per kwh which hopefully wouldn't ever apply for the snow melt system, ha ha.

Wonderful, we just rolled over to winter rates, went down to $.137/KW, Summer rate was $.159/KW.

 

[JesseN]

Nice find on the Tyco website.

And $0.04/kw-hr seems really low. Did you remember to factor in the 'delivery cost'? Electric utilities (around here) now split the cost of the electricity itself away from the 'delivery' cost of that electricty flowing though their wires (and switches and transformers and so on).

Those are the prices here in Nebraska. A benefit of being the only state that still has 100% public power (no private companys) is that since the utilities are not for profit, the rates stay low.

My bill has about $30 for the generic service fee just for having service. I figure I'm gonna have that regardless of whether I use radiant heat or not so I didn't include it in my figures.

Hi Jesse
Where in NE are you? I'm near Scottsbluff. I ran your numbers thru a Radiantworks Pro program that I used to design the radiant floor in my shop. I don't know what type of a snowmelt system you are planning, either electric mat or electric heated liquid in tubing. Either way, the heat load should be similar. Using the design parameters of -8 def F, 9mph wind speed, 36" of snow/day(1.5"/hr) and 6729 deg days, is spit out a load of 230 BTU/hr/sq ft. Based on this, I would guess that you are low in your estimate.

Cheers
Steve

I'm in Falls City, the far SE corner of the state. I'm not sure where to look up the design paramenters for my area? Can I find these online somewhere?

Thanks for the info!

 

[stingry]

Here's the site that I got the program from:

http://www.wattsradiant.com/support/radiantworks/
you can download the program by filling out a registration, submitting it and they will send you a password to download (this is how it worked a couple of years ago). The program has a calculator for snowmelt systems. Somewhere, there is a place where you enter your zip and it will tell you the design parameters for your area.

Hope this helps
Steve

 

[Jackfre]

Check out Rehau.com as well. There is an excellent design manual for radiant.

Public owned utilities? Cheaper rates with no privately owned utilities? I didn't think there were that many democrats in Nebraska:

 

[JesseN]

Here's the site that I got the program from:

http://www.wattsradiant.com/support/radiantworks/
you can download the program by filling out a registration, submitting it and they will send you a password to download (this is how it worked a couple of years ago). The program has a calculator for snowmelt systems. Somewhere, there is a place where you enter your zip and it will tell you the design parameters for your area.

Hope this helps
Steve

Awesome. I downloaded the program and have been trying it out for a little while. Very cool to see how things affect the overall heat load in real time. With my design parameters used and only using it as a class 1 snow melt system, i came up with just under 100,000 BTUs required. However, I have also realized that I should have used shorter loops for the snow melt system. My loops are all 1/2" pex and around 280' long, using a 50/50 mix I come up with a crazy high head loss.

 

[BadgerBoilerMN]

{QUOTE]Hi Jesse
Where in NE are you? I'm near Scottsbluff. I ran your numbers thru a Radiantworks Pro program that I used to design the radiant floor in my shop. I don't know what type of a snowmelt system you are planning, either electric mat or electric heated liquid in tubing. Either way, the heat load should be similar. Using the design parameters of -8 def F, 9mph wind speed, 36" of snow/day(1.5"/hr) and 6729 deg days, is spit out a load of 230 BTU/hr/sq ft. Based on this, I would guess that you are low in your estimate.

Cheers
Steve"[/QUOTE]

You can download the program, but it can't remind you that it almost never snows when it is -8°F. The output and subsequent performance of any snow melting system is determined by local conditions and the particular application. Commercial walks and helipads get one specification while residential driveways and sidewalks typically get a more modest snow melting design.

Consequently, Jessse's numbers are quite accurate. I too pay .o4/kW here in our Minneapolis area CO-OP, where we design and install residential driveway snow melting systems regularly and normally quote and annual cost to melt 50 inches of snow at $.25/sf. At our current $.65/therm rates the actual cost would closer to $.21/sf of driveway per year.

Electricity nearly always costs more than natural gas and even at a special "off-peak" electric rate in our almost rural CO-OP, the cost of a square foot of snow melt this year will be $.45/foot. I myself, have a new walk covered with pavers on an electric boiler and concrete driveway driven by a condensing natural gas boiler starting up this winter and will be keeping track.

We have designed and installed many snow melting systems, but nothing focuses the mind like your own dollars burning.

And back to design:

However, I have also realized that I should have used shorter loops for the snow melt system. My loops are all 1/2" pex and around 280' long, using a 50/50 mix I come up with a crazy high head loss.

Those are long loops for sure, but one should know that a 50/50 mix of propylene glycol anti-freeze is one of those "rules of thumb" that have been obsolete for some time. A much lower mix could be used lowering the viscosity of the blend, making it easier to pump and increasing heat transfer at once.

Unless you are planning on melting 1.5" of snow per hour (a snow storm by all standards) at -8°F with a 15mph wind you will likely not need a 50/50 mix of anti-freeze or 250btuh/sf of driveway either. At least I never have in the 25 years or so we have been designing residential snow melting systems from the Sierras to Buffalo.

A little professional help in the beginning can save more time and money than a straight DIY snow melting job, even if you have the software.

PS. We never use electric wire for snow melting since once buried can't be changed. With a hydronic PEX system, any fuel can be used to feed the snow melting boiler.