Propane or electric heat pump

[DuaneBoyce]

I am building a new house and trying to decide on propane furnace with a/c or electric heat pump. If i go with propane i will use it for my cooking and hotwater heater if not it will be totally electric. I am going to buy an outdoor wood boiler to use during the coldest months. which would be better and cheapest to run. [img]/forums/images/icons/confused.gif[/img]

[Nat]

From all the info I have found the heat pump is the most effeciant dollar for dollar. with the temperature in WV close to here in NC I would expect the same. I ain't going to say that the warmth is the same, but the temp in the house will be as warm as with any other method, and you don't have to buy an air conditioner, since the HP does both heating and air conditioning.HTH, later, Nat

[Bird]

I have a brother-in-law in the southern tip of West Virginia who had a heat pump installed this summer. Another brother-in-law in the Dallas area had a heat pump in a house several years ago. They both think that's the best way to go. I hope they're right because I'm supposed to close on buying a housse a week from now and it has a Rheem heat pump. [img]/forums/images/icons/wink.gif[/img]

[Pat]

Bird is going to get Rheemed... OK. Better than being run down by a Trane.

There is not likely to be a huge difference in cost for heating whether you go propane or heatpump but a propane heater can't cool you. Do you experience many power outages of any decent duration such as to make electric heat pumps need a backup? I have heat pumps but also have propane back up heaters in a few locations.

Below about 40 degrees a heat pump's efficiency drops so dramatically that electric heater strips are used to provide heat in most installations. If you have significant weather below 40F you will have a high electric bill. I have a propane fired furnace as my air handler for the heat pump. At temps below the outside thermostat's set point the heat pump shuts down and the propane furnace takes over. You set that thermostat acording to the relative costs of electricity vs propane and the efficiency curves of the respective units. For us is has been about 38F.

Irrespective of your choice of heat, better than minimum recommended insulation WILL PAY FOR ITSELF in offset energy costs. In fact, if you follow the more stringent energy conservation guidelines for super insulation, low infiltration, high efficiency heating and cooling systems it doesn't matter much which energy source you select as you won't be using much of it. If you can heat your house with a candle and cool it with an ice cube the kind of candle isn't important.

We are a dual fuel household. Even our range is dual fuel. Gas burners on top and electric ovens. We have heatpumps but backup propane units as it isn't fun to be heatless for a few days in the aftermath of an icestorm. I have a hot water tank that is heated by one of the heatpumps at about 1/4 to 1/3 the cost of running an electric hot water heater. This tank feeds a propane fired water heater. If we have electricity we have LOTS of hot water (Jacuzi tub) but it the electric is off we still get hot water from the gas fired unit (just showers, no Jacuzzi.)

High R-values and low infiltration (think blower door test) are more important than selecting electricity vs propane in many instances.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[Bird]

Yep, Pat, the fellow I hired to check out that Rheem system and teach me a little bit about it said it was a good one down to about 40 and below that the electric element comes on. I knew that, but he also said if you adjust the thermostat upwards (we very rarely change ours) to not go up more than 3 degrees at a time or the electric heat would kick in to try to raise the temperature more quickly.

[GaryM]

Pat,

Backup propane for power outages? You telling me that your standby generator won't handle your heatpumps electrical load?

I have an electric resistance furnace, which the generator won't handle. Thinking of switching to a heat pump so we can have AC or heat if the power goes out. The generator handles the AC fine, so the heatpump shouldn't be an issue. (Those heat strips might be an issue though)

[Pat]

Bird, Sounds like you did the right thing, again. Yeah, that is about the typical limit of freon/compressor technology. Below about 40F heatpump heating can get quite expensive. A good (more recent manufacture) unit will have a SEER of at least 12 or hopefuly better. Federal mandate was only 10 untill recently, then 12. My Lennox units are 19.2 SEER. A good heatpump is 300-400% efficient compared to straight electric heat untill the outside temp gets too low (or way too high.)

How do you get more than 100% efficiency??? Electric heat like when your heater strips come on in your heat pump is 100% efficient as all the electricity is made into heat. With a heat pump you are mostly "pumping" existing heat from one place to another, not making heat. It only takes about 1/3 to 1/4 as much electricity to pump it as to make it. In winter, any energy lost to heat in the process is still a good thing. In summer any losses are losses since you are trying to make "cool."

Depending on how much time your outside thermometer spends at or below 40 degrees you might be $ ahead to have a backup heat source other than those heater strips inside your heatpump. Maybe a gas log, decorative AND functional or other gas fired heater, wood stove, insert or...

I personally don't like and will not recommend vent free gas heaters except in certain specific circumstances and conditions which are not usually met. Direct vent is my favorite. Combustion air comes from outside and the burned gas and fumes go back ouitside. They can't backdraft into the living spaces and constitute virtually no CO threat and do not compete with occupants for the oxygen in the room air. They also don't cause condensation on windows and other cool interior surfaces or require you to "crack" a window for fresh air. Good central systems (including heatpumps) add some fresh air to the interior spaces as they operate. This is called "make up air."

If you tighten up a house very well to elliminate infiltration you significantly increase overall energy efficiency but inrease the risk of "sick house" syndrome. With all the formaldehyde and other polutants in the materials our homes are made of and furnished with, indoor polution is often worse that outdoor polution. You need a sufficient number of air changes to keep healthy conditions indoors. There is an answer to the dillema of the mutually exclusive goals of well sealed house for efficiency and fresh air exchange for health.

ERV or HRV Energy or Heat Recovery Ventilator. It is a ballanced dual air circuit ventilator. Usually a single motor turns a couple squirrel cage fans, one at each end of the motor shaft. One exhausts air from the house and the other brings fresh air in. The two air streams do not mix but do both pass through an air to air heat exchanger. In summer your expensively conditioned cool and dry air is exhausted through the HRV where it cools the incoming fresh air so you don't loose your cool that you paid for. In winter the heated air being exhausted warms the incoming air so the heat you paid for gets recycled.

I have one of these and it takes less than an amp to run it and is essentially maint free. The difference between ERV and HRV is whether or not it also transfers humidity (latent heat) as well as heat (sensible heat.) A unit with humidity exchange costs a bit more and was not justifiable in my climate as the trade off calcs showed it to be a wash. Further south and I would have a different result. My unit is an HRV and only exchanges heat, no moisture. To get into details of the ERV involves latent heat and enthalpy discussions. Google at your leisure for details.

Retrofiting these units is easy. Although I have some separate grills in the house it isn't required. You can easilly tap into existing ducts and there will be no visible alterations requiring touchup paint. If you have vented sofits you might not have to have any externally visible grills either.

I like these systems because they give you a constant fresh air supply without running up your heat and cooling costs. I have "Yed" some exhaust grills together and have one above the Jacuzzi tub, another above the comode (instead of a switched exhaust fan), another in the shower ceiling, and one in the back of the walk-in closets. These remove any steam and create a gentle drift of air from the rest of the house into the bathroom where the air is discarded. The fresh air that replaces the exhausted air goes into the center of the house (great room)

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[Pat]

Gary, That is the "prezact fact!" My genny will not run my three heatpumps. I have no immediate plans for getting a larger genny.

If St. Louis temps fall down around freezing and your grid goes down you may be in for a rude suprise. Those heater strips will probably take at least twice the Watts (if not 3-4 times) the draw of the heatpump. Given that a good heatpump is 300-400% efficient, replacing it with resistive heating should take 3-4 times the Watts.

Don't worry about us freezing in the dark in case of winter time power outage. One of our heatpumps is a geothermal unit and doesn't care how hot or cold the outside air is. The other two have propane furnaces as their air handlers and don't try to run as heatpumps below our calculated breakeven setpoint of 38F. I can manually interveene and switch to propane vs heatpump should I choose to do so, suh as during a power outage even if the temp is in the 50's or whatever.

My genny will handle the air handlers and electric ignition. There is a gas log fireplace in the great room. We have five propane burners on the range where only the ovens are electric so we will have hot chow. The range in the basement has a gas oven if we are overwhelmed with the need to bake during an outage. There are decorative but operable gas log parlor stoves in the sitting room, sun room, and basement. We will not be restricted to one small huddling space around a can of Sterno. There is a 3-0 door between the sitting room and the bedroom so heat can filter into the bedroom. There is an in-line duct fan between a ceiling grill in the sitting room and a ceiling grill in the bedroom. It has a three mode switch: on, off, and thermostat. This will share heat between the bedroom and sitting room even if the connecting door is closed. It will let the sitting room's parlor stove heat the bedroom too. The duct fan is way under an amp draw.

My guess is that burning propane in a stove is more efficient for heating a living space than burning it in a generator outside and running the electricity inside. All the heat of the engine is wasted fuel. Engine maint should be a bigger deal than propane gas log maint. I have no problems with your system. It sounds like a good one. I'm not sure you have an adequate backup heating arrangement. Will your genny run your central system with the heater strips fired up? That isn't an issue here since we don't have heater strips because we opted for using propane furnaces as air handlers for the air to air heatpumps.

I need to conserve electrical generator capacity during an extended outage so I can run more power on the HF rig.
If things got realy bad I could always use my camper. It has extensive PV on the roof and a propane genny as well as central heat and satellite TV. I suppose I could park it next to the house and run a cord to the sub panel under the tractor shed to electrify some of the house circuits. If I wanted to I could plumb in a propane connection so I could plug the camper's propane system into the houses supply (2 each 1000 gal tanks for 1600 gal usable) That would run the frige/freezer in the camper for a loooooong time so we would not be in joepardy of losing a gal of ice cream.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[CJDave]

[img]/forums/images/icons/smile.gif[/img] Pat.....I'm getting a picture in my mind of you and your family huddled around a can of Sterno. [img]/forums/images/icons/crazy.gif[/img] We are all double-wired here and just recently I have completed the final phase of the "Critical Loads" electrical system. I'm going to be dumping the main breaker that is on our "household-use" subpanel and see how we like living on the "critical loads" panel; which feeds the gas furnace, the fridge, the microwave, the gas kitchen stove igniters, and a few lights. I've never actually tested to see how many amps all that will take so we can selecte a propane-powered Gen Set. I'm thinking that we could build a generator room with a pair of twelve-cylinder Cats with paralling and changeover gear. Ooops!! I forgot myself there for a minute....I'm not doing that kind of work anymore...dang it! [img]/forums/images/icons/crazy.gif[/img]

[Pat]

CJDave, You said that "We are all double-wired here" and the first thing that came to mind was a lot funnier than anyone huddled around a can of Sterno. I was seeing nervous caffeine addicts downing prodigious quantities of black coffee while waiting for the double strength expresso to finish brewing.

I have a small but adequate stock of special incendiary devices, some sort of pyrotechnic mix on the end of a combustible handle that can be ignighted with friction and used to light a gas burner. Will also light a can of Sterno if needed.

I analyzed our emergency needs and opted, for the present, to only reallize a rather Spartan subset of circuits. All of our central heat and air zones are in the NICE TO HAVE category but are not actually critical. In fact we don't need the central system at all in an emergency. We have enough propane heaters distributed around to keep us quite comfortable and prevent any burst pipes. If I chose to park our camper next to the tractor shed I could have all the lighting we need from solar power or alternatively run its propane genny as an alternative to our gas fired back up genny. Using the camper's genny, connected to our residential propane tanks, would elliminate having to handle gasoline and refill the backup generator's tank and elliminate the need to refil the campers two small tanks.

Note: In clear weather the camper's PV array can get 12-14 amps of charge into 330 AH of batts at nominal 12 VDC. Enough to power several fluorescent lights, entertainment electronics, and keep the batts topped off for the coming night. This is about 200 Watts with ideal conditions. Even with overcast skies, the cells I chose will produce a useable charge. Enough to run a few lights and keep the 330AH batts topped off. A few advantages to solar backup are: quiet, no refueling, no exhaust fumes, no oil changes or other engine maint. A couple donwnsides are: expensive for much power, have to keep the panels free from excessive snow and ice.

Going all electric with no gas (LPG) or other backup is not the ULTIMATE survival system. If for any reason you loose the grid for an extended period it is altogether likely that natural gas distribution (often pumped with electricity) will fail as well.

I feel fairly secure having a combination of backup systems including solar and LPG. When I designed my mom's ALL ELECTRIC home with heat pump I included a gas log fireplace and an LPG connection on her sun porch with a quick connect that feeds a small portable 3 burner stove top removed from an old motorhome. In case of an extended outage she can have hot chow and a warm house.

We don't get extended outages very often. The last one was 5 years ago and lasted 3 days at our location. Quite near here some folks were out for weeks. They are not on or quite near a MAIN LINE as we are so they aren't a high pri repair.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]