Gas furnace or electric heat pump

indebt · Sep 8, 2005

I am building a new house and I am trying to decide on propane furnace with ac or electric heatpump . Which should have the cheapist operating cost? I should also add I am buying an outdoor wood boiler to use during coldest 3 months of the year. If I go with propane I will use a gas stove and waterheater as well if not it will be totally electric.
All opinions welcome /forums/images/graemlins/confused.gif

bczoom · Sep 8, 2005

Duane,

A couple questions/thoughts.
Have you checked with your electrical supplier to see what discounts are offered if you have an all-electric house (don't mention the outdoor furnace to them)? I have an all-ele house and get a great rate in the winter.

Can you hook up your HW tank to the outside boiler as well (at least when the boiler is running)?

If you go with an outdoor furnace, the strip heat in the furnace should rarily (if ever) come on. That's good since it's probably the biggest ele. draw.

Is your electric generated from a nuclear plant and therefore (supposedly) not tied to fossil fuel prices from year to year?

I have an all-ele house but heat (as much as I can) with wood. The new heat pumps are very efficient. For a family of 4 and heating/AC, TV's, HW, lights... runs me around $120/month average (3000+ sq/ft).

Brian

slowrev · Sep 8, 2005

Duanne,
In your area a high efficiency heat pump is the cheapest operating way to go. also Electricity prices seem to be rising a bit slower than propane prices. Of course you could go the best possible of ways a heat pump with a gas pack backup. the gas portion would work if your heat pump dies and will work below the temp that your heat pump looses efficiency.
Also if you lost power in the winter it takes a BIG generator to run a heat pump, but not very much wattage is needed to run a gas furnace.

Ben

bczoom · Sep 8, 2005

( Of course you could go the best possible of ways a heat pump with a gas pack backup. the gas portion would work if your heat pump dies and will work below the temp that your heat pump looses efficiency.
Also if you lost power in the winter it takes a BIG generator to run a heat pump, but not very much wattage is needed to run a gas furnace.

Ben )

Ben,

If he has the outdoor wood burner, wouldn't that do everything the gas would? I would also think a medium sized (7000w) generator could run the air handler blower as well as the pump for the outdoor furnace.

Brian

Highbeam · Sep 8, 2005

I would go the heat pump route. Fossil fuels may come and go but electric will always be here. Nuclear power, it's what's next.

slowrev · Sep 8, 2005

Yep forgot about the outdoor wood heater.

Of course if you are going to use a wood boiler for heat, are you going to used forced air system or radaitor/ radiant type of heat in the home ? In that case a propane indoor boiler would be best.
Ben

kenmac · Sep 8, 2005

If you go propane furnace,buy the highest efficiency unit you can buy.I think around 95-96% efficient is the highest. this is also true with heat pump buy the highest seer you can afford .It will cost more up front , but will pay for its self in the long haul.

Egon · Sep 9, 2005

The questions asked are not really definable as we can't see into the future.

As it is a new house I would ensure all systems are too code.

To choose a system use information from reliable HVAC people who are familiar with all the aspects.

Also note that wood may seem free but isn't. There is cost involved in cutting, splitting and hauling. It will also require more attention.

If I were a wise man or had the proper credentials I could answere the question but meet neither criteria.

Egon

Volfandt · Sep 9, 2005

I have both! In my area a heat pump is efficient around 70% of the time during winter. It looses it efficiency at approx 30 degrees and thats when the backup heat source kicks in and in my case that is a natural gas furnace.

When I originally built, I heated with a Sears heatpump (hp) w/internal electric resistance heaters and it did a pretty good and inexpensive job up until the elec heaters kicked in, then the meter would spin so fast that I thought it would take off like a Helo. When it was cold but not cold enough to kick in those heaters it always felt like it was blowing cool air. You'd have to step outside then back in to feel any warmth in it /forums/images/graemlins/grin.gif
Since a HP generally heats the air to the same temp as your skin, approx 98 degrees, thats why it doesn't feel like hot air.

After 13 yrs of good reliable service, it needed replaced and I decided to go with another split system but this time utilize natural gas as the backup. I went with a Carrier Puron heatpump & 98% efficient gas furnace split system.

Pluses:
Heating,
1) the air is always warm.
2) the system utilizes an outside thermostat to kick in the furnance. At approx 35 degrees the HP cuts off and it runs as a std gas furnace.
3) it has a time of day setback thermostat that allows up to 3 different temp settings.

Cooling,
1) Puron seems to work as well as freon as evidenced by lower electric usage and the house stays a comfortable (to us) 72 degrees.
2) the larger but slower turning outside unit fan is very quiet. My patio is a mere 10' away and when the compressor & fan kicks in, we don't have to raise our voices to speak.

Negatives:
Heating,
Natural gas is expensive!!! /forums/images/graemlins/mad.gif They've raised the price every yr since I installed the new unit. The lower elec usage is more than offset by the increased gas prices.

Cooling,
The HP seems to run all the time which is amazing in that it uses less electircity than the older unit it replaced.
I only included this as a negative as I feel something that runs constantly will use up it's designed lifespan quicker but of course if it lasts 13 yrs or more than this will be a moot point.

Bottom line, having had a HP in two differnt houses over the course of 23 yrs I knew that I wanted to continue to use a HP but wanted something other than electirc resistence heaters as backup.
If I had it to do over again, I'd have priced a propane furnace as well as an oil fired furnace and went with the cheaper of the 3.

Volfandt

techman · Sep 9, 2005

( I have both! In my area a heat pump is efficient around 70% of the time during winter. It looses it efficiency at approx 30 degrees and thats when the backup heat source kicks in and in my case that is a natural gas furnace.

Volfandt
)

I often read this and need to correct what is a misleading statement. Modern heat pumps will deliver 2 watts of heat for every watt of electrical power in the mid teens. So efficiency at this temperature is still 200% as compared to electric resistance. So in reality the efficiency does not decline much with a heat pump. The problem that occurs is that the capacity of the heat pump (number of BTUs delivered) drops. This is due to the reduced temperature difference between the vaporizing freon in the outside unit and the outdoor temperature, reducing the amount of heat that can be absorbed from the air. The lower temperatures also reduce the compressor load, and thus the electrical input, so efficiency does not drop dramatically. One could oversize the heat pump to minimize this problem, but it would be way too oversized for A/C, causing poor performance in the summer.

paul