Would one of you electron benders please tell me how I go about computing cost of operation of an appliance if I know that it operates on 220vac at
2,000 w and 'y' is the cost of electricity/ Kwh. Is there a time factor tied to the 2,000 (- too many years)? I'm thinking of supplementing the shop's LPG heat with electric thinking that it would be cheaper than just using the gas alone. I only heat on an as-needed basis but the last fill up nearly cost me a good internal organ!
Ed's final answer is correct...............note the units in his reply
30=A2 per hour
but his calc needs a slight correction to be dimensionally correct
2000 watts (2 kW) at .15 kW =3D 30=A2 per hour
S/B
2000 watts X 1 kW /(1000 watts) X 15=A2 / kWatt hr =3D 30=A2 / hr
giving the cost to operate an electrical device in =A2 or $ per hour makes the most sense, that way the user can easily determine the cost since he has a good idea of the total time of usage.
Watts is an instantaneous figure; no time factor. So w/1000 x y = cost per kWh. E.G. 2000 W heater, cost is $0.10 per kWh. So 2000/1000 x $0.10/kWh = 2kW x $.10/kWh = $0.20/h
That probably doesn't tell you much because you won't know how many hours the 2Kw heater will run in a month. Nontheless, heating with electricity is likely to be less costly than heating with LPG. Somebody could tell you the BTU per gallon of LPG and the BTU for a kilowatt of electricity and then you could apply your local cost per gallon of LPG and per kWh of electricity to see which would be cheaper.
Compare cost of your gas price to your electric price by btu. for me in the midwest electric is stlll apx 50% more expensive than Ng, only you know your costs. Btu comparisons or for Lp are online. In other words how much is your cost for 100000 btu for each. You likely will see Lp is best, but it depends on your area.
I presume they must vent the exhaust outdoors, so what's a reasonable number for the percentage of BTUs in the gas that actually heats the workspace?
Does it vary significantly with the design (and era of manufacture) of the LPG heater?
I expect that electric heat must be near 100% efficient, huh?
The original question of "tell me how I go about computing cost of operation of an appliance" can only be answered by knowing how many BTUs he needs. Then he can figure out how long an electric heater will have to run. All that calculating isn't necessary. All he has to do is multiply his gas usage by his heater's efficiency, then divide that by 3,413 to find out how many KWs he needs.
Right OP didnt say what his lpg heater is so how can you figure a comparison without knowing its efficiency. Im sure its as efficient as Ng and there are many types and ratings so he could have junk running
40% efficiency or a ventless 99% or furnace at 60-94.5% eficiency Electric is 100% efficient.
One thing that bugs me about gas furnace/heater efficiency is how they calculate it.
My gas furnace is 80 percent which I assume means that the 80 percent of the BTU's in the gas end up in the house side of the heat exchanger, i.e, useable heat.
But I don't think they ever consider the heat loss from the the vents. How many BTU's are lost through the the two openings of 100 square inches each, one at the floor and one at the ceiling. The flow of air through these vents is continous
24 hours a day. The furnace may put 80 percent of the heat into the house, but how much heat is lost through those vent openings? The greater the difference between inside temperature and outside temperature, the greater the total heat loss. Maybe that is why they don't estimate that loss.
I could imagine that at 0 degrees, as much as 50 percent of the heat could be lost. In other words, at 80 percent AFUE furnace would actually result in only 40 percent of the heat retained in the house compared to Electric heat which would be
But he does not know how to figure the operating cost of those kWs. He seems to know what he needs, (thus the 2,000 watt figure) just not the cost of operation compared to propane.
When you say vents do you mean exuast up the chimney, Im sure its calculated in in Afue rating. The big increase in condensing units is the powered vent, exterior air, and of course second exchanger. But an interesting fact is the efficiency difference between an 80% and
95% furnace is not 15 % its an 18.75% increase, time to think again.
If vents are in attic or in walls that leak out the attic or a cold crawlspace yes, you loose a bit yes. Dont run it 24x7 and insulate , I insulated ducts and blew in foam in the walls above in wall registers, I blew out a few walls too with the expanding foam.
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