Math Whiz Needed

[frugalityisgood]

Anyone can help me to understand this. I have a heat pump which uses electricity to take the heat from the outside air and heat a coil. Which then the blower on the furnace blows over it and heats the house. The trouble is I've done some calculations and it appears that natural gas provides more kilowatt hours for less money and if my calculations is correct, it's cheaper to use gas then to use electricity.

1 therm = 29.300111111111 Kilowatts

My last gas bill I used

29.29 therms
Cost - $41.25
Cost per therm - 1.4083304882212359166951177876408

Locally depending upon amount used, the cost per kilowatt goes from 9 cents to 11 cents. So I average at 10 cents.


So 10 cents multiplied by 29.300111111111 kilowatts, equals $2.93

To get the same amount of energy with gas I used one therm. Which 1 therm cost only $1.40. So dividing 1.40 by 29.30, I get 0.04 per kilowatt. So by using gas I'm only paying 0.04 cents per kilowatt compared with electricity I'm paying 0.09 or 0.10.

So the question becomes if this is true. If I got a generator that ran on natural gas. I could power my house and feed it back into the power grid and make a profit.

I think my calculations are wrong though. But if this is true. The Power company is probably using natural gas to power it's generators.

[JohnH]

Hello,

I can help but I'm struggling to understand what you wrote.

Here is where I am up to...

You used 29.29 therms of gas.

Your bill was $41.25

That is $1.41 per therm or $1.41 per 29.3 kWh.

Is there other charges on the bill like a standing charge or tax? You need to deduct that from the bill to calculate the price per therm.

You then state an average figure of 10c per kilowatt. Is that for electricity?

You don't say how much electricity your heat pump uses and if it heats your house in the same way as the gas does.

The kW used by the heat pump will not generate the same amount of heat in kW.

Is there a power rating for the heat pump in Watts? And how many hours is it on for?

I need more information to complete your calculations.

[EnergyBoomer]

I think about energy in British Thermal Units (BTUs)

Gas
29.9 therms
100,000 BTU/therm
2,990,000 BTU in 29.9 therm
2.99 that is million BTU
$41.25 cost for 29.9 therms
$13.80 $ per million BTU

Electric
3412 BTU / kWh
0.003412 Million BTU per kWh
$0.10 cost per kWh
$29.31 $ per million BTU

The cost per million BTU of energy for electric is more than twice the cost of gas.

The trick with heat pumps is the heat energy is free of cost. It comes from the great outdoors. The electric is used just to move it indoors. You get more heat into the house than you would get by converting the electric used directly into heat. Heat pumps are more than 100% energy efficient.

They range for 200 to 300% efficent depending on the design.

By the way the electric companies do use natural gas to make power in the summer time. When air conditioning loads push the demand up they use gas turbine engines to drive generators. They are like huge jet engines.

[mommy4ever]

We looked into geothermal heat. I spoke with dear old dad, who attended a seminar. And due to our location(too far north by about 300kms), it would cost us over double to run the heat pumps as it would to continue using gas.

But out of curiosity, since we have some one here who is understanding how to calculate.

I have a question too! we have a gas furnace. Our gas bill at the moment is about $70/mo. Because we run a wood burning fireplace insert to warm the house. Our furnace only runds on average 1 time a day, in the morning before we restart the fire if it went out. Our wood is free, cut offs we collect(with permission) from the construction sites, that are otherwised headed to the landfill.

But our power is higher, I don't know how much higher. I'll need to find an old bill, pre-fireplace insert. to see the difference. i am wondering is there is a savings in using it. It is just a 110 fan, not sure what it's rated at. But we do keep the house warmed that we would with gas. it's so cozy here. So nice when it's -30ºC outside, to a nice coze warm house. If I had the ratings, could you help see the cost of running it?

[frugalityisgood]

Very good info and helpful.

My house was built in 1887 and has no insulation and it can be quite drafty.

When the temps are above 38 degrees the heat pump does well. Get below that and it has to kick over to the gas furnace occasionally. And the colder it gets the more it has to kick over to gas. The trouble is it might run for 10 minutes and not raise the temperature in the house. Sometimes the temperature actually has gone down. So it is as if the heat pump waisting electricity because it is not warming the house at all.

After looking at the cost of natural gas. I figured it could possibly be cheaper to just run the gas furnace alone when it gets really cold and not have both a huge electric bill with a huge gas bill.

It's presently a lovely 7 degrees outside and the gas furnace seems to be doing a more efficient job of heating then the heat pump would at this temperature.

Thanks again for the info.

I think about energy in British Thermal Units (BTUs)

Gas
29.9 therms
100,000 BTU/therm
2,990,000 BTU in 29.9 therm
2.99 that is million BTU
$41.25 cost for 29.9 therms
$13.80 $ per million BTU

Electric
3412 BTU / kWh
0.003412 Million BTU per kWh
$0.10 cost per kWh
$29.31 $ per million BTU

The cost per million BTU of energy for electric is more than twice the cost of gas.

The trick with heat pumps is the heat energy is free of cost. It comes from the great outdoors. The electric is used just to move it indoors. You get more heat into the house than you would get by converting the electric used directly into heat. Heat pumps are more than 100% energy efficient.

They range for 200 to 300% efficent depending on the design.

By the way the electric companies do use natural gas to make power in the summer time. When air conditioning loads push the demand up they use gas turbine engines to drive generators. They are like huge jet engines.

[EnergyBoomer]

The information you provided is too incomplete for a fully detailed answer, but....

I am guessing that your gas furnace has an electric powered blower that runs only when the furnace does. It pushes the warm air through out the house.

The free wood fueled fireplace insert has a small electric fan that runs almost all the time to push warm air out into the room. Right?

The two electric fans almost off set each other, the furnace fan motor is bigger but the fireplace fan runs more. So the big difference is the fuel.

Free wood vs paid for gas. The winner is free wood.

[mommy4ever]

The information you provided is too incomplete for a fully detailed answer, but....

I am guessing that your gas furnace has an electric powered blower that runs only when the furnace does. It pushes the warm air through out the house.

The free wood fueled fireplace insert has a small electric fan that runs almost all the time to push warm air out into the room. Right?

The two electric fans almost off set each other, the furnace fan motor is bigger but the fireplace fan runs more. So the big difference is the fuel.

Free wood vs paid for gas. The winner is free wood.

Yes, the insert has a fan the runs as soon as the box hits the set temp, and circulates the air. It's on a level where there are heating ducts in the ceiling. It distributes the heat to the top lever(2 half levels up), goes up the stairs to the next half level, the one lower is cooler, but keeps it reasonable.

The furnace fan only runs when the furnace kicks in. It is a high efficiency that is self firing, meaningno pilot. So we use very little gas unless it's running.

We pay the same rate now as we did 4 years ago, we locked in at a fairly cheap rate for both gas and power.

I'll see what I can find in the manuals at what it rates for power consumption, but you're right, the power is likely the same, the fuel is the savings.

[Squirt]

The idea of using a generator for your power and feeding it back to the utility lines is incorrect- You must disconnect from utilities (using a transfer switch, automatic or manual) before you use a generator. If you don't, you'll most likely blow somebody or something up.



I've read repeatedly that heat pumps are only "good" when the difference between the temperature outside and the temp inside is small. The farther you want those temps to be from each other, the less efficient a heat pump will be. This is why few people use them in climates like where I live- super hot in the summer and super cold in the winter!

[mommy4ever]

I was referring to geothermal heat, heat pulled from underground below the frostline. Not a generator. Same principle as the first poster, but from the ground, not the air.