What is the Cost to Run a Hydronic Radiant Snow Melt System in Toronto?
Hydronic Radiant Snow Melt Systems have been around forever. The stigma about them is that they cost too much to run. When you do a little math you will soon find out that they cost less to run than mechanical snow removal services using snow plows and blowers. These plows may damage your surfaces and the chemicals will kill off your plants and grass come spring. And where do you put all that snow? Not to mention your hydronic radiant snow melt will start melting the snow when the first flakes hit the sensor not 3 hours later by which time you fell twice.
To really find out the cost to run a hydronic radiant snow melt system before the fact you need to do a little math based upon some facts and not too wild assumptions. The following example of a 1,000 sq’ radiant snow melt system in Toronto is the most frequently inquired about snow melt size.
1,000 ft² Radiant Snow Melt System Parameters.
This is an estimate and the numbers here are not set in stone as it is impossible to predict the numbers, hours, temperature of a coming year’s snow falls. We will therefore work with the following numbers:
- The area to have snow melt is 1,000 ft²
- The heat requirement is 150,000 BTU/h meaning every single square of the snow melt needs 150 BTU supplied to it in an hour to reliable melt the snow no matter the realistic outside temperature.
- The pick up load (the original warm up to melting temperatures) of the slab will be 400,000 BTU every time the snow melt system runs. A 6″ thick concrete slab needs 15 BTU/ft² to warm up by 1 °F based upon the specific heat of concrete being 0.23 BTU/Lb/°F
- The slab is well insulated with R10 value insulation from below.
- The supply and return lines are insulated to and from the manifolds.
- 3/4″ diameter O² Barrier PEX tubing is used at 9″ spacing 6″ below the surface of the slab.
- At the start of the snow melt cycle the slab is at -10C.
- The system will run for 8 hours at a time to melt and evaporate the snow.
- The cost of 1,000,000 BTU energy using a natural gas boiler running at 95% efficiency is $35.84
Now the math.
400,000 BTU pickup load + 8 hour run time x 150,000 BTU for melting =1,600,000 BTU
This means since 1,000,000 BTU costs $35.84 the total cost per melt will be 1.6 x $35.84 = $ 57.34
Since the cost of Natural Gas delivered to you gets cheaper the more you consume, this $35.84 will be less since you are most likely already using gas for heating your house, domestic hot water and cooking. This $57.34 therefore is the worst case scenario as cost to run a hydronic radiant snow melt system once goes. Realistically you are faced with $40/8 hours melt in real world scenarios.
How about preparing for the snow to fall?
If you know that a storm is coming you can use the advanced snow melt controls to preheat (idle) the slab to something just below freezing. When the snow starts to fall it will only need to bump the temperature up a couple of degrees not start from -10C if that’s what the slab temperature would be without heating. This will eat more gas of course but will speed up the melt considerably. Of course if no snow shows up all that gas was burned for nothing.
What can upset this apple cart?
There are several potential pitfalls as far as the running time and therefore the costs are concerned which can negatively affect the cost to run a hydronic radiant snow melt system
- The slab is not insulated properly. In this case much of the heat will go down into the ground only making the gophers happy.
- The supply and return from the boiler is not insulated properly. You will be heating the air instead of the slab.
- The driveway is not properly graded allowing melt water to pool in spots instead of running off the slab. It will turn your driveway into a skating rink once the snow melt sensor is dry and the system shuts off.
- The side of the slab is exposed and not against the soil. The heat will go sideways instead of up around the edges not melting the snow there.
- The loops of PEX tubing are too long. More than 250 ft/loop is a bad idea. By the time the glycol reach the last portion of the tube it is ice cold and will not melt the snow.
- The boiler or pipes at the boiler loop are undersized. In this case the boiler will not be able to keep up with the heat requirement especially on colder days and the snow will just sit there while the boiler burns through copious amounts of gas
- The PEX tubing is too far spaced apart or too small in diameter. The snow will not melt and the boiler will run and run and run eating gas for no reason.
This is how it looks when a system is well designed and put together. The snow doesn’t lie.