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-   -   Cost-Benefit for electric vs heat pump, do my calculations look sound? (http://www.diychatroom.com/f17/cost-benefit-electric-vs-heat-pump-do-my-calculations-look-sound-78515/)

chazman113 08-11-2010 06:34 PM

Cost-Benefit for electric vs heat pump, do my calculations look sound?
 
I have a 2 story house and am thinking about how to heat up the recently finished upstairs (2 bedroom and attic). It seems to me (especially because I wont be up there a whole lot and I dont have any more money) that electric zone-heating is the way to go for now

Assume $150 heating 1st floor a month with heat pump (My electric cost is fairly cheap)
Upstairs is half the size, so $75/mo

So monthly cost with heat pump - $75/mo
With Electric (Assume twice as much power) - $150/mo
I live in delaware, assume 4 months a year needs heat

Base Cost of electric heat - $400

Base Cost of heat pump - $6000

Extra Cost = 4 * 75 = $300/yr

Break Even = 5600 / 300 - 18.6 years!

This of course assumes electric doesn't go up (Which it will) but it also doesn't
take into account that I can easily forgo heating one room with the electric option.

beenthere 08-12-2010 05:57 AM

Your electric baseboard will be closer to 3 times as much as the heat pump cost.

chazman113 08-12-2010 08:32 AM

Fair enough, that's still 9 years.

Yoyizit 08-12-2010 12:00 PM

Quote:

Originally Posted by chazman113 (Post 484239)
This of course assumes electric doesn't go up (Which it will)

For the next level of complexity, and to make a real Decision Tree, attach a probability to the cost of elec. going up and then tweak the numbers to find out how at what point you would change your decision.

Then, to become a real Jedi warrior, fire up your spreadsheet and add the cost of maintenance/repairs, with likelihoods, to each option.

You gonna' stay in that house more than the 7 year average?

chazman113 08-12-2010 12:15 PM

Agreed. I happen to be a programmer, do you want graphs, maybe I can somehow use recursion and a large database as well?

I do intend to stay for 7 years. Really, if these heaters are used for 7 years and I get a heat pump later that is fine.
  • Heat pumps may be better in 7 years
  • It will last that much longer if I get it 7 years from now
  • Upfront cost of electric heaters is trivial
  • I intend to barely every use 50% of the upstairs for atleast 3-5 years, except when guests are around or until I have kids. Realistically, the other half I will probably leave around 60F and crank it up if I want to use it.

Daniel Holzman 08-12-2010 03:25 PM

The only other hitch in your computations is whether you have an adequately sized electric service to install new electric heat upstairs. They draw a fair amount of power, if it pushes you over the installed capacity of your system you need to figure in the upgrade cost for electric service.

chazman113 08-12-2010 03:28 PM

Tru tru, I dont think there is a problem there, but will definitely make sure.

COLDIRON 08-12-2010 05:49 PM

I would install baseboard electric heaters and check the insulation in the attic it might be worth adding another layer.

Make sure the windows are sealed properly.

Are you installing the heaters yourself? If so it's relatively an easy job with virtually no maintenance.

With heat pumps you are at the mercy of air conditioning companies.

If a baseboard thermostat or heater goes bad just go to a big orange store or the one that starts with L and buy a new baseboard like and kind.

Most of the time you can use 2-- 2 pole 20amp 220volt circuit breakers depending upon the requirement.

chazman113 08-12-2010 08:38 PM

I tend to agree, I can still get 30% tax credit for more insulation. I have r19 now and I layed plywood down in hopes of extra storage. looks like i have way more than ill need now. think i can just roll out more unsided insulation over the plywood of like 75% of the attic and it will be effective? I still need a little of the attic to keep large stuff

zootjeff 08-13-2010 03:33 AM

Quote:

Originally Posted by chazman113 (Post 484239)
I have a 2 story house and am thinking about how to heat up the recently finished upstairs (2 bedroom and attic). It seems to me (especially because I wont be up there a whole lot and I dont have any more money) that electric zone-heating is the way to go for now

Assume $150 heating 1st floor a month with heat pump (My electric cost is fairly cheap)
Upstairs is half the size, so $75/mo

So monthly cost with heat pump - $75/mo
With Electric (Assume twice as much power) - $150/mo
I live in delaware, assume 4 months a year needs heat

Base Cost of electric heat - $400

Base Cost of heat pump - $6000

Extra Cost = 4 * 75 = $300/yr

Break Even = 5600 / 300 - 18.6 years!

This of course assumes electric doesn't go up (Which it will) but it also doesn't
take into account that I can easily forgo heating one room with the electric option.

You might want to read some of my threads:

http://www.diychatroom.com/f17/heatp...adsheet-62047/

for energy analysis.. I calculate closer to 3x to 5x for the heat pump vs baseboards..


And for your 6000 dollar section, you could consider doing it yourself like I did..
http://www.diychatroom.com/f17/duct-...ddition-47710/

chazman113 08-13-2010 08:38 AM

Will look at it, the heat pump downstairs is just big enough for the first floor, so I cant retrofit

Yoyizit 08-13-2010 01:41 PM

Quote:

Originally Posted by chazman113 (Post 484628)
Agreed. I happen to be a programmer, do you want graphs, maybe I can somehow use recursion and a large database as well?

Doing projects that required recursion were very difficult for me (in Pascal). :(
I guess this is a problem for linear programming or operations research.

chazman113 08-13-2010 03:47 PM

I'm very tempted to make a web calculator. Thank god I'm too lazy to stoop to that level of nerdiness.

Yoyizit 08-13-2010 04:37 PM

Quote:

Originally Posted by chazman113 (Post 485269)
to make a web calculator

If you build it they will come! :laughing:

There is a lot of demand for such a thing.
I guess a rigorous version would include the cost of money, the investment horizon, the present value of an annuity, etc.


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