Electric furnaces not made large enough for house?

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Old 07-28-19, 08:03 AM
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Electric furnaces not made large enough for house?

Hello everyone,

I live in a 2100 sq ft house with a 30+ year old furnace that I'm looking into replacing. It does not provide information on Kw or BTU on the current furnace. According to some websites I saw online, I need 50-55 btu/sq ft based on being in zone 5.

2100*(50-55) = ~100,000 - 115,000 btu

Is this correct? The largest electric furnace I'm finding is 68,000 btu.
Maybe this explains the outrageous electric bill in the winter?

Thank you,
Scott
 
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Old 07-28-19, 09:17 AM
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Maybe this explains the outrageous electric bill in the winter?
Electric is going to be the most expensive way to heat your house unless you are also using off-peak. If you are going to replace your furnace I would recommend looking at a gas (propane or NG) with the possible addition of a heat pump depending on your location.
 
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Old 07-28-19, 09:51 AM
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The area we live doesn't have access to natural gas
 
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Old 07-28-19, 09:54 AM
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What area do you live in?
Here in the southeast [with TVA power] they say a heat pump is the most efficient.

Propane might also be an option.
 
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Old 07-28-19, 10:43 AM
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I'm in a rural area near Chicago. I don't own the house, so I'm trying not to spend too much money. Is 68,000 btu the largest electric furnace I can get?
 
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Old 07-28-19, 01:50 PM
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First, there is no chart or graph that exists that will tell you what size equipment you need for X size house. You need a manual J to calculate heat load.
If your using straight electric resistance heat I’d look into adding a heat pump to it even in Chicago. Could take a lot off your electric bill.
 
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Old 07-28-19, 04:38 PM
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Two sides to this coin, heat generation and heat loss. Addressing the heat loss has some low cost high return aspects, like air sealing both the house and all heat ducts. Once sealed you can add some insulation where possible. if you have a basement and access to the perimeter of that ceiling then insulation and caulking can make a big difference.

Bud
 
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Old 07-28-19, 04:42 PM
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The area we live doesn't have access to natural gas
Neither do I. That is why I also said propane.

If you are renting then I would not be doing anything. You can buy space heaters or baseboard and zone the house better than using an electric furnace.

What is your heating now?
 
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Old 07-28-19, 06:10 PM
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You also need to look at the other side of the coin. A 68,000 BTU electric heater would require 84A at 240v. A very costly solution

For your area you'd need to look into an efficient heat pump with probably 10k of backup heat.
 
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Last edited by PJmax; 08-01-19 at 08:08 PM. Reason: whoops..... incorrect formula used.
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Old 07-30-19, 04:04 AM
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To @PJMax; you forgot the 3.4 BTU/watt in your computation. (about 84 amps)
 
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Old 07-31-19, 04:04 AM
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I am not sure what your thinking is that replacing an electric furnace would change the cost to heat your home.
Electric heat is 100% efficient and the size of the furnace has no impact on efficiency.
The only effect size would have is run time which could efffect comfort but not heating cost.
A way to get a rough idea as to your furnace size is to check on the capacity of individual banks of elements if yours is wired this way.

Also, a way to get a rough idea how closely the furnace size matches the load is to make a note of how long it runs on average to heat your home in the coldest weather.
Some furnaces have a low-high setting to turn off one or two banks of elements during milder weather.
 
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Old 07-31-19, 09:33 AM
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My home was built 21 years ago. and is located just north of Pittsburgh, Pa. It is a well insulated 1 story ranch with 2000 sq ft. on the first floor. We finished the basement 15+ years ago, so the total heated area is now 4000 sq ft. We heat both floors with a 2 stage 95+ efficiency gas furnace with 80,000 btu output on high heat and about 60,000 btu output on low fire. The furnace has never run on the high heat output. We heat both floors to 72 degrees in the winter. This may help you determine the size of the furnace or the amount of heat required. for your home. However, if you are a renter, replacing the heat source is not your responsibility nor is up-grading the insulation or replacing the windows. If your heating bill is too high you should probably find a new set of digs. One last thing; a 68,000 Btu furnace uses 20KW of electricity and requires 83.33 amps To find the size of your furnace you could count the number of heat strips They are usually rated at 5 KW (5000 Watts) each.
 
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Old 08-17-19, 07:54 AM
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The largest electric furnace I'm finding is 68,000 btu.

Electric furnaces are typically sized by wattage such as 15 KW or 20 KW and not BTUs. Like others have already stated, the 68,000 BTU furnace would be a 20 KW furnace. 15, 20 and 25 KW electric furnaces are easily found, but I wouldn't want to pay the electric bill to use one although I love electric heat. If I were faced with replacing a large electric furnace, I would also be looking at a heat pump.
 
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