Radiant Heat costs

[GoodStuff]

Just finished constructing a 40x6016 pole barn in Central Kentucky with a 14x24 extension on the back. The slab is 5" thick, and I installed 10 loops 245' long (253' of you count the tubing coming out of the slab to the manifold). After much research, I have chosen to use Mike Bloomington's shop as a blueprint for the radiant, and have purchased Grundfos circulator pumps and etc. to build an exact replica of Mike's system. I have a 27KW Ecosmart on demand water heater to power the radiant.

The shop has 320 amp service. The slab is insulated with 2"XPS under, and around the exterior of the building (8" deep). The ceiling is metal panel and I will be blowing 24" of pink stuff above. The walls will eventually have 2" XPS between the poles, and then book-cased walls filled with R13 (this will be the last part of the project after all electric, air, water, and etc. is complete...

The question I have for everybody is... what kind of electric costs can I expect? There are those who are going to scream that I am using a water heater instead of a boiler - I understand the arguments... I do have propane available and could switch to a propane boiler setup - but I'm afraid the gas costs will be stunningly higher than the electric usage... What do you guys think?

 

[anythingyoucanimagine]

Sounds like you might have some free real estate up on the roof for panels. Both kinds (electric and water).

 

[Lonnies Performance]

Electricity can vary depending on your location.

For me it's $.12 per KW... I see some say on here they are at $.16 per KW.

27KW x .12 = $3.24/hr running.

1 KW/hr = 3412.142 BTU/hr

27KW = 92,127.8 BTU's

Propane also varies from $1.75-$3/gal,
1 gal = 91,547 BTU's/gal

27KW = 1.006 gal propane/hr

Propane is typically cheaper, but how much depends on your price.

At $3/gal 27KW of energy costs $3.02/hr worst case.
Also you need to calculate the boiler efficiency with propane.
Divide the cost/hr by efficiency

$3.02/.8 for 80% efficiency.... some energy goes out the chimney.
=$4.775/hr vs. $3.24/hr electric at $.12/KW


Plug in your local costs & see how much it saves.

 

[GoodStuff]

Electricity can vary depending on your location.

For me it's $.12 per KW... I see some say on here they are at $.16 per KW.

27KW x .12 = $3.24/hr running.

1 KW/hr = 3412.142 BTU/hr

27KW = 92,127.8 BTU's

Propane also varies from $1.75-$3/gal,
1 gal = 91,547 BTU's/gal

27KW = 1.006 gal propane/hr

Propane is typically cheaper, but how much depends on your price.

At $3/gal 27KW of energy costs $3.02/hr worst case.
Also you need to calculate the boiler efficiency with propane.
Divide the cost/hr by efficiency

$3.02/.8 for 80% efficiency.... some energy goes out the chimney.
=$4.775/hr vs. $3.24/hr electric at $.12/KW


Plug in your local costs & see how much it saves.

You’re awesome! Once the slab is up to temperature I can’t imagine the radiant system working much… Anybody who has radiant know what the run times are on average?


Sent from my iPhone using The Garage Journal mobile app

 

[nsula_country]

I have 2 Ecosmart units in our house for total domestic water needs. Also on a 320 service.

No idea on cost. But, I figured my 20Kw electric heat in shop in <$3/hr... Heat pump to follow, just haven't sweated it in.

Plan to add a 27Kw Ecosmart in shop for general domestic use and brewing and hot water supply to power washer.

CT

 

[yeldogt]

Once the slab is up to temperature I can’t imagine the radiant system working much…

??

Radiant does not change thermodynamics. Your building needs "X" amount of BTU's -- it needs "X" amounts of BTU's. You are not using less BTU's with radiant. Whatever heat source you pick needs to work just as hard to overcome the load on the building

Where you can save some BTU's with radiant is in buildings with very high ceiling --when you compare radiant to forced air. Since radiant is heating low and slowly cooling as the heat rises you tend to use less BTU"s vs forced air that overheats the ceiling. I have done many radiant spaces .. you don't do it to save money.

You can find simple heat load calculators on the internet -- plug your building into the calculator ... it will give you the BTU's needed on the coldest design day. That's the boiler size needed for the building. You can then get what is called "degree day" .. this will give you the BTU's you will need over a period of time to maintain the temp in your building. This is how long the boiler is going to run for the whole season based on your climate (That's how an oil company figures a delivery cycle -- the know the climate -- your building and heater. They use the outside temp to determine how much oil you have used.

It's then just a mater of plugging that BTU number into different fuel costs -- the fuel calculator is very simple and can give you the different costs for electric and propane.

Radiant does have a delay load as the slab heats -- but you have to keep heating it with the building load or it will cool. This is why setback soon;t work well with radiant ... and why insulation is so important under a slab

 

[Verado1250]

I did the Menard's system, though I built it myself and have a propane micro condensing boiler from them. I put my system in service Nov. 1, 2018 and put an hour meter on it to see how often it runs. I document the reading every morning. As of now, my hour meter is showing 48 hrs. Obviously with the cold snap last week it ran more than it has since. I think on the coldest day last week, -5 deg. overnight, the system ran for about 4 hours in a 24 hour span. The thermostat is kept at 50 deg. My shop is 40x68x14 and well insulated. I put the hour meter in to try to determine how much propane I use per hour. I had my 500 gal. tank filled (80%) last August and marked the position of the needle on the site glass. The needle has barely moved. I am anticipating I will only leave the system on until app. March 1, so overall, I think for my needs, the system has outperformed my expectations. If the cost of propane is low in mid-summer, I will go ahead and have the tank topped off again, as it does not cost any more to keep a tank full. If the price per gallon is high, I think I will have more than enough to get me by for another winter or two. The boiler is the only appliance on the propane.

 

[Dante6889]

You need to accurately calculate what it will be for you. Propane generators, solar panels or electric.

Many do not praise the solar panels for many reasons, I recommend to buy them if you allow money, you'll save a little, but do not really count on them.

 

[stevelh]

Southern Indiana here. 40x60x14 vaulted ceiling. 2” insulation under slab, spray foamed walls, blown in sinsulation above ceiling. Installed a navien ncb-180e condensing boiler with two zones. Thought that I would hardly use any propane so I had the largest propane tank you can install next to a building (100 gal.) I believe. This is our first winter and have had to fill it every 5-6 weeks so far, just had our 4th fill. Had the boiler checked and it’s running at 98.2% efficiency. Waiting for good weather to get a 500 gal tank set. Overall not what I was expecting for such a larger investment. Hope your setup works better for you.

 

[finn]

568 gallons of propane so far to heat my 48’x75’ shop to ~47 degrees with a 98% efficient boiler. Last fill was on or about February 1. I bump it to ~60 when working.

A 16’x60’ lean to part of the footprint isn’t heated,

Prepaid propane was $1.44/gallon. Street price is now $1.59.

 

[Lonnies Performance]

Wow... I've been seeing quotes locally in the $2.20-$2.40 range from many suppliers & the local refill place at $2.87. I would be ecstatic at $1.44.

Due to a back ordered 1000 gal tank, I'm feeding my building off of two 100# tanks (23.5 gal ea), which is not economical. I could easily use 2 tanks a week with a set point in the low 50's.

I found it cheaper to run my mini-splits some each day to offset the boiler run time for a lot less money. Paying an additional $100/mo. in electric saved me $300 in propane.