Another heat source question (Natural Gas or Electric)

[srdaniel]

I'm trying to decided between Natural Gas and Electric heat for my detached garage. My current planned usage is only for when I need to work in the garage, not all winter long. Usually only 5-10 nights per month, depending on when my friends or my own vehicles break down.

Notes on garage:

• Location Trempealeau Wisconsin
• Size is 28x36x8
• I recently installed and insulated the ceiling (currently only R19 but I want to blow in some more when I can afford it)
• Walls already insulated (not sure on R value, assuming R13)
• Still have to replace single pane window
• Still need to seal service door better
• Replaced garage door seals
• Electric feed is from a 60amp breaker in house basement
• No existing water or gas service
• Distance from house ~20 feet

Questions about Natural Gas

1. I plan on calling my gas company about these questions.
2. Can I run the gas line from my house basement through the foundation or do I have to connect the gas line outside my house tee'ed to the meter (and then to the garage)?
   • Side note, if I have to connect outside the house after the meter, I will have to dig under a fence, under a deck, and under a sidewalk. If I can connect through the house foundation, I would have to go under a sidewalk and a small pond and be a longer distance.
3. How deep do gas lines have to be (I've read everything from 20" to 30")?
4. How much can I do myself vs. requiring gas company or licensed person to do? (Dig trench, lay pipe/tubing, connect fittings etc). Yes, I would not dig without calling diggers hotline.

Notes on Natural Gas

My last months bill was 0.6835 ¢ per therm

Questions about Electric

• Will my existing electrical box handle a 5000 (or 7500) watt heater?
• Current setup
  • 20 amp for garage door openers
  • 20 amp for north and west wall outlets
  • 20 amp for south and east wall outlets
  • 15 amp for all lights
  • unused 30 amp dual gang (someday I'd like to add a welder, preferably arc (no idea on requirements here))
  • garage is feed from a 60amp breaker in the house
  • garage electrical box is rated at 125amp max

Notes on Electric in my area

Cost per kwh for me (according to this xcel pdf)

June—September 11.3780 ¢
October—May 10.2920 ¢


Models I was thinking about

Eletric: Fahrenheat Ceiling Mount Automatic Electrical Garage Heater

My simple math showed this might cost me about $1 an hour to run (please verify this for me, I never was good at math).

Natural Gas: Mr. Heater Big Maxx Natural Gas Unit Garage Heater

My simple math doesn't know how to calculate this cost per hour to run.


Any thoughts anyone?

 

[thammel]

I'll keep this very short....natural gas is typically a LOT cheaper than direct electric heat. If you don't have natural gas, then a heat pump with electric back-up heat is you next best option. The heat pump is about 3 times more efficient than direct electric heat. The back up heaters with a heat pump only come on when it's very cold outside and the heat pump can't supply enough heat.

Tom

 

[Shocker]

No brainer on the natural gas.

Also, it is cool that you can get 10 nights in week.

 

[srdaniel]

No brainer on the natural gas.

Also, it is cool that you can get 10 nights in week.

Yea that was supposed to be "month".

 

[tomroblee]

Gas is going to be cheaper to operate.

A therm is 100,000 btu.
A watt is 3.41214 btu

You say that gas costs you $.68per therm. At $.10 per kwh, electricity is going to cost you about $2.93 per therm.

You should also note that the electric and gas heaters you are comparing are vastly different in heat output. A 5,000 watt electric heater will put out about 17,000 btu per hour. A 7,500 watt heater will put out about 25,000 btu per hour. The link to the gas heaters showed a 45,000 btu and a 75,000 btu heater. I would imagine that those ratings are input (the amount of gas that you burn) ratings. The output is probably about 80% of the rated input.

If you will only be using the heat for a few hours at a time I would imagine that you would want a heater large enough to heat the garage fairly quickly.

I'm guessing that you calculated your gas and electric rates by dividing you bill by the number of therms or kwh. Most utilities charge a flat base rate to cover that cost of their equipment, reading the meters, billing etc. On top of the flat charge there is a variable charge based on the amount of gas or electricity actually used. This is frequently a step rate---meaning that your rate drops as you use more. It is quite possible that the cost of adding additional load will be a fair amount less that the rates you quoted.

It sounds like a 7500 watt electric heater might be pushing you to the limits of your electric service---depending on what you are actually using in the garage at one time.