Heating costs

[Travis Porter]

I have gotten to thinking about heating costs.

If I have a heater that say uses 17 amps at 220 volts that would be 374 watts per hour (I think). If I pay 18 cents a megawatt then for it is costing me 18 cents for every 3 hours the thing runs and doesn't shut off. Right?

With heat pumps you use SEER and HSPF to determine efficiency. What is the efficiency of electric heat? The thing may use 17 amps, but it isn't 100 percent efficient or is it and how do you know?

 

[Outa Square]

try this link

http://www.csgnetwork.com/energycostcalc.html

 

[WoodWrangler]

I don't know how to figure this out ... but I'd like to know too. I went ahead and ordered the heater that Woodartz was walking about from Northern Tool ... and hope it works and is cheaper than my kerosene.

 

[Outa Square]

based on the average price of electricity being $0.1017 a Kilowatt hour and heater like woodartz is 4000 watt heater. It would cost $.41 cent a hour to run a heater like that.

 

[thrytis]

I think your decimal points are off. I believe electric heat (generated by resistance, not transfer of heat like a heat pump) is 100% efficient. A 220 volt 17 amp heater than uses 3740 watts per hour (power = current x voltage at 100% efficiency, i think). You are probably paying $0.18 per KWH, not MWH (my rate at least is about $0.08/KWH), which would be about $0.67/hour of continual use.

 

[Jim Murphy]

I have gotten to thinking about heating costs.

If I have a heater that say uses 17 amps at 220 volts that would be 374 watts per hour (I think). If I pay 18 cents a megawatt then for it is costing me 18 cents for every 3 hours the thing runs and doesn't shut off. Right?

With heat pumps you use SEER and HSPF to determine efficiency. What is the efficiency of electric heat? The thing may use 17 amps, but it isn't 100 percent efficient or is it and how do you know?

17*230= almost 4000 watts (if you measure the voltage, you'll find it closer to 230 than 220). That's 4 kilowatts. You pay closer to 18 cents per kilowatt hour. So, running that heater for three hours would burn 12 Kwh, which at your rate would cost you $2.16.

The better number to work with is Kwh and cost per Kwh. In your case, it costs you 4 X 18 (that's 72 cents) per hour to operate.

Watts is ALWAYS volts multiplied by amperes. Electricity is always charged per kilowatt hour.

SEER is an acronym for Seasonal Energy Efficiency Rating (or Ratio, I forget), and it applies to air conditioning efficiency. HSPF is the same thing, but applies to heat (not cooling). The efficiency of a compressor type unit is a measure of how many BTUs of heat are supplied (or removed) per kilowatt of electricity used.

HSPF and SEER only apply to compressor technology. Resistance heat efficiency (in other words, red hot wires) , for all intents and purposes, is the same. The more amps you pull, the more heat you get, and the more it costs, but it doesn't run as long. HSPF would NOT apply to resistance units.

Consider two heat pumps. Both draw 20 amperes, requiring about 4.6 Kw to operate. But one produces 20,000 BTUs per hour while the more efficient produces 30,000 BTUs per hour. Obviously, the more efficient unit would run less, and therefore cost less to operate. But both have the same wattage rating.

Clear?

 

[Joe Scharle]

Sounds about right. I've had one of those Northerns for about 3 years and once they warm the space, they do cycle. Electric resistance heating is close to 100% efficient for kw consumed, while heat pumps are heat exchangers and are even far more efficient.

 

[Travis Porter]

Eric, you are right, I got the decimal off, so it is going to be about .42 cents an hour if a kilowatt hour is .17, but it should cycle, which ties back to how well a shop is insulated and how much heat loss you have as to how much it is going to have to run to maintain the temperature once it gets it established.

 

[Travis Porter]

17*230= almost 4000 watts (if you measure the voltage, you'll find it closer to 230 than 220). That's 4 kilowatts. You pay closer to 18 cents per kilowatt hour. So, running that heater for three hours would burn 12 Kwh, which at your rate would cost you $2.16.

The better number to work with is Kwh and cost per Kwh. In your case, it costs you 4 X 18 (that's 72 cents) per hour to operate.

Watts is ALWAYS volts multiplied by amperes. Electricity is always charged per kilowatt hour.

SEER is an acronym for Seasonal Energy Efficiency Rating (or Ratio, I forget), and it applies to air conditioning efficiency. HSPF is the same thing, but applies to heat (not cooling). The efficiency of a compressor type unit is a measure of how many BTUs of heat are supplied (or removed) per kilowatt of electricity used.

HSPF and SEER only apply to compressor technology. Resistance heat efficiency (in other words, red hot wires) , for all intents and purposes, is the same. The more amps you pull, the more heat you get, and the more it costs, but it doesn't run as long. HSPF would NOT apply to resistance units.

Consider two heat pumps. Both draw 20 amperes, requiring about 4.6 Kw to operate. But one produces 20,000 BTUs per hour while the more efficient produces 30,000 BTUs per hour. Obviously, the more efficient unit would run less, and therefore cost less to operate. But both have the same wattage rating.

Clear?

As mud. You have now switched to BTU's and I was into Watts.:dontknow: How do you know how many BTU's a unit generates, say like the electric heat units others have been looking into?

 

[Joe Scharle]

Travis, look at this site and punch in some variables. It'll clear up a lot of your Qs.

http://www.heatershop.com/btu_calculator.htm

 

[Jim Murphy]

Joe, that's a great site. One key element is the watts <-> BTU converter.

Propane generates 92000 BTUs per gallon... it takes about 27000 watts (27 Kw) to generate that same heat output in a resistance heater. My last delivery of propane (with customer owned tank) was $2.05 gallon, my Progress Energy rate is about 11 cents per kwh.

(Y'all know I love math)

According to Joe's website, my shop needs 32000 BTUs to raise the temperature 20° in an hour. That's about 9.3 Kwh. At current rates, it would cost about 68 cents/hour to operate with propane, and $1.02 for electricity. Natural gas is priced in therms, where 1 therm is 100,000 BTUs. I don't have a current price for NG, but in June of 2007 Scana/PSNC announced a price increase to $1.31/therm. If you have nat gas available, your cost for the same garage would be 42 cents/hour.

Now, the site Joe linked does not indicate if that value is the BTU required to make up the heat loss per hour at certain temperature differentials (which is my best guess), or the BTU needed to raise the indoor temperature from X to Y, where X is 45° and Y is 70°.

A Carrier heat pump like you find in a motel room (that is, without ducts/returns/etc) generates 11,600 BTUs at a current draw of 3.6 Kw. Be aware that these types of heat pump units are NOT efficient. The EER of a unit like this is around 3. The one you have heating your house is at least a 10, maybe a 14 or 15 if you've replaced it lately.

A 1.5 ton (18,000 BTU) heat pump like you would install stand-alone for the shop will consume 2Kw. However, this does not include the "emergency heat" that will kick in anytime the difference between room temperature and thermostat setting exceeds 3°. In other words, you hit the shop, it's 50° inside, you turn the heat pump on to 65°. The resistance emergency strips will come on, even if the outside temp is 68°. Also, when the outside temp falls below about 42°, regardless of the difference between room and thermostat setting, the resistance heater strips will come on. This makes a big difference, as most strip heaters in a heat pump are 5 Kw.

So, to compare the various sources of shop heat, let's make a table (we're woodworkers, right? So a table should be a snap.)

SYSTEM COST/100,000 BTU
-------- ----------------
RESISTANCE ELECTRIC....... $ 3.21
NATURAL GAS ...............$ 1.31
PROPANE ...................$ 2.23
WINDOW HEAT PUMP ..........$ 3.41
DEDICATED HEAT PUMP .......$ 1.22


The costs are based on the current average values for the various sources of energy that I cited above, and as always, YMMV.

 

[DavidF]

Excellent write up Jim! All the numbers match my findings of about 0.50 per hour for my Dayton heater. I don't use it much so going that route removed the upfront cost of other forms of heating. I spent just over $130 for the heater and I have not been disappointed.

 

[walnutjerry]

I do not know how to figure that but...........I have 1500 sq. ft. in my shop with 10' ceiling. There is 6" insulation overhead and supposedly foam in the 8" block walls.
Last month my electric bill was 180.00----highest it has ever been. Last year the highest was 120.00 and that was only one time, rest of the time it was 60.---80.00.

Tell me why the big increase????????????

It is a heat pump but I had the strips put on a switch and they have not been turned on.

Jerry

 

[Travis Porter]

Clarity!!!! The differences are a bit surprising. I would have thought natural gas and propane would have been much closer in cost.