Announcement

Collapse
No announcement yet.

Electric or gas furnace

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Electric or gas furnace

    In December 2020 I had a 10.8 kw DC, ground mount system installed. (No batteries)

    The installation company calculated a smaller system based on our last three years consumption, but I asked to have a slightly larger system put in as I knew I would make changes after the installation to use more electricity.

    I currently have an LP gas furnace and hot water heater which I planned to replace with electric once we had the panels in.

    I would like to hear opinions on whether making the change from gas to electric is the right move. To me, it is a no-brainer, but I have read on other forums that it isn't the right move, so now I'm not sure.

    I would love to hear from anyone and everyone who has an opinion, experience, comments, more questions, .....

  • #2
    That is tough to do, requiring a really big solar system. On the other hand, I have seen
    propane rise from $1 a gallon in summer, to over $5 in Feb. Modern inverter driven
    variable speed heat pumps have a chance, multiplying your electric energy several times
    over the input.

    Start by getting a handle on your heating energy, and your solar production. My basic
    rule is, 27 KWH about equal the energy of a gallon of propane, maybe 25 KWH with
    a high efficiency furnace. Get out your energy history and check it out. The energy
    multiplying and minimum operation temp of heat pumps vary widely. I manage to
    do it here with a solar production of 29,000 KWH/year, NET METERING and NOT
    batteries make it possible. good luck, Bruce Roe

    Comment


    • #3
      I agree with Bruce that the first step is getting a handle on heating energy. I replaced a natural gas water heater with a heat pump water heater. It offered some advantages to my particular situation. I am on a favorable TOU rate which allowed me to get credited at high rates for kWhs I stored on the grid and run the heat pump at lower rates that were as much as three times less expensive than the energy I stored those kWhrs at. Your mileage may vary. As you have already discovered, opinions will also vary.
      Last edited by Ampster; 02-21-2021, 08:48 PM.
      9 kW solar. Driving EVs since 2012

      Comment


      • #4


        It is important to compare energy sources on an apples to apples basis.

        The best way to do that is to compare the equivalent BTU capability of all available energy sources.

        Here are the comparisons of energy sources from lowest cost to highest:


        Wood……….….......1 rick hardwood....cost $65 per rick delivered............value per mBTU $5.20


        Coal……………........1 ton Anthracite....cost $225 per ton delivered..........value per mBTU $8.09

        Propane…………....1 gal......................cost $0.99 per gal delivered….......value per mBTU $11.85....(summer fill for the last 3 years was under $1 per gal)

        Nat Gas……....…....1 Therm.................cost $1.20 per therm delivered....value per mBTU $12.00

        Wholesale Electricity...1 kWh....................cost $0.046 per kWh wholesale.....value per mBTU $13.51....(sale price to POCO less production cost)

        Gasoline…..……....1 gal.......................cost $2.36 per gal.........................value per mBTU $20.70

        Heating Oil #2......1gal........................cost $2.89 per gal........................value per mBTU $20.87

        Retail Electricity...1 kWh…….….…........cost $0.106 per kWh retail….........value per mBTU $31.06

        Comment


        • #5
          You didn't say where you are located. Florida doesn't require much heat. Maine requires a lot of heat.

          When you mention an electric heater, are you thinking a heat pump or resistance heating? Heat pumps are more expensive but produce much more heat per watt of electricity, often 10X (HSPF=10). They are also more practical in temperate climates like Georgia than frigid places like Maine.

          Do you have netmetering for your solar? If so, you are getting paid for every watt you don't use. That may be helpful to pay for LP.

          What will a heating system cost? What is the power company paying you for excess energy and what do you pay for consumed electricity? What are you paying for LP? Bruce gives you equivalence factors for electricity vs LP. Heat pumps can be rated with a COP factor or an efficiency factor or HSPF or SEER.

          After you get these numbers, simple math will be helpful. All of these things allow you to calculate the time required to repay your investment in a new heating system, assuming that it is even cost effective compared to LP. I'm 99% confident that resistance heating will not be cost-effective ever, unless you are in a tropical climate. Heat pumps are a major investment, but may be worth it.
          7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

          Comment


          • #6
            Depending on your winter heating load, a heat pump for space heat makes a whole lot more sense than straight electric resistance heat. Period. See DanS26's chart. A heat pump may make sense for heating if you can get one that has a C.O.P. > 3 and can wring ~3X as much heat out of a kWh of electricity as straight resistance heating and so reduce the fuel cost proportionately and probably below using nat. gas. That'll make more sense in a warmer climate. Reason: As the outside air temp. drops, the heat pump C.O.P. drops. So just when you need higher C.O.P.'s to get the cost of heating down, that C.O.P. is at lower efficiency points on its operating curve. In some cold climates, say > 7000 F. heating degree days/yr. or so, it may likely be more cost effective to heat with nat. gas or propane.

            I've lived with air source heat pumps, nat gas and propane fired furnaces. In mild climates with warm summers, heat pumps wil have a somewhat higher C.O.P. and be more cost effective at heating than a heat pump and so offer the most cost effective way to go with the added benefit of summer A/C thrown into the deal. In colder climates, nat. gas is the way I went for heating, one reason being the fast(er) room warm up times as well as overall comfort. Besides, the gas heating equipment is less complicated.

            Comment


            • #7
              Originally posted by bob-n View Post
              You didn't say where you are located. Florida doesn't require much heat. Maine requires a lot of heat.

              When you mention an electric heater, are you thinking a heat pump or resistance heating? Heat pumps are more expensive but produce much more heat per watt of electricity, often 10X (HSPF=10).
              You sure about that ? Looks like you're saying a good heat pump can put out 10 times as much heat as plain old electric resistance heating for the same energy input.

              Not true.

              Divide the 10 by 3.412 for the correct number.

              Comment


              • #8
                This is all good stuff (not that I understand it all, but I will research everything to make sure I understand it). To answer a couple questions I should have included in my first post...

                I live in Wisconsin. I do get net-metering and get paid for over-production above and beyond, but because my provider is a cooperative, they don't pay me retail price so over-production isn't really worth talking about.

                I will start studying my heating energy. As far as what type of heat (heat pump or resistance heat) I was leaning toward resistance heat, more than likely an electric furnace since the ductwork is already in place. I don't want to put out the money for geothermal heat pump and from what I've read an air-source heat pump may not be the best solution for periods like the last few weeks or so where we seldom saw temps above zero. But, that is why I am here, to learn from people who know and can set me straight. I won't do baseboard, but am interested in Infrared for space heating and a little boost here and there. Yes? No?

                Please keep replying and feeding me answers and info. I appreciate all the replies so far. Thank you.

                Comment


                • #9
                  If you are thinking resistance heat - forget it, unless you and your offspring have $$ to pay every month. With a heat pump, it's resistance heater only kicks on in the coldest days.
                  Are you on a well or city water. A well, brings your ground heat right up to you, wastes some water, have to have a place to dump cold water
                  Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                  || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                  || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                  solar: http://tinyurl.com/LMR-Solar
                  gen: http://tinyurl.com/LMR-Lister

                  Comment


                  • #10
                    Originally posted by EMKETART View Post
                    This is all good stuff (not that I understand it all, but I will research everything to make sure I understand it). To answer a couple questions I should have included in my first post...

                    I live in Wisconsin. I do get net-metering and get paid for over-production above and beyond, but because my provider is a cooperative, they don't pay me retail price so over-production isn't really worth talking about.

                    I will start studying my heating energy. As far as what type of heat (heat pump or resistance heat) I was leaning toward resistance heat, more than likely an electric furnace since the ductwork is already in place. I don't want to put out the money for geothermal heat pump and from what I've read an air-source heat pump may not be the best solution for periods like the last few weeks or so where we seldom saw temps above zero. But, that is why I am here, to learn from people who know and can set me straight. I won't do baseboard, but am interested in Infrared for space heating and a little boost here and there. Yes? No?

                    Please keep replying and feeding me answers and info. I appreciate all the replies so far. Thank you.
                    If you're thinking about electric resistance heat, you better have pretty deep pockets. If you don't have nat. gas avail., consider propane. Depending on where you are in WI, a heat pump may be viable, but takes some research and education to avoid mistakes based on ignorance and then getting taken to the cleaners by salespeople.

                    Whatever your choice, you will be $$ ahead if you first get/perform an energy audit and implement the biggest /most cost effective of the recommended measures in the audit before getting any new HVAC equipment. That way, your bills will be reduced by what's probably the most cost effective means (conservation) and any new equipment that's subsequently sized to the new (lower) heating load will be more correctly sized, that is, not sized to the old (larger) heating load and will then operate more efficiently and, being smaller, probably less expensive to acquire as well.

                    Here's the sequence:
                    Education in HVAC load calculations and education of pros/cons of various types/methods of meeting HVAC residential loads.
                    Determine current heat load both by examining prior use and residential load analysis.
                    Energy audit. Often offered free by POCOs and coops. Give yours a call.
                    Use your education to estimate possible load reductions from audit recommended measures and possible fuel cost savings (or additional fuel/electricity costs) of various methods of meeting your new (lower) heat load.
                    Determine what type of heating method fits your goals, lifestyle and budget, considering the equipment cost but paying more attention to lifetime fuel costs and the cost in time/toil/$$ of maintenance over the equipment's lifetime.
                    Get several quotes from reputable equipment installers of equipment for your choice of equipment.
                    Never ask a peddler a question for which you don't already know the answer. If you learn something new from a peddler, great, but informed buyers get screwed less.

                    As you'll find in your education, electric resistance heat in a cold climate is about the most expensive way to provide space heat to a home in a cold(er) climate. Small spot heaters, OK, an entire home, no way. Infrared heating is a little better but still mostly for spot/small applications.

                    Good luck.

                    Comment


                    • #11
                      Here 20 miles south of WIS border, we do not see temps much lower than
                      -12 F, occasionally -20F, but usually for only brief periods. I am able to deal
                      with that entirely using 6 late model zone air-to-air heat pumps chosen for high
                      efficiency and low temp capability. With WIS and MN temps hitting -30F at
                      times, I think you had best keep your gas furnace for worst case. HOWEVER,
                      you may be able to avoid the gas 10 months of the year and also achieve
                      air conditioning on a much upgraded basis, to the limits of your solar array
                      production, with carefully chosen heat pumps. Here is the temp performance
                      of one HP, starting to drop off at 4 F, and perhaps down to 70% at -13F.
                      Not shown is the drop in COP with lower temps, but unlike resistance heat,
                      it will immediately bounce back with any daily temp increase.

                      MUZFHrange.png

                      The basic HVAC load here was around 1100 gallons of propane a year, and
                      some much varying KWH for air cond summers. The solar array was chosen
                      with those in mind, remembering 27 KWH = 1 gallon of propane. The energy
                      multiplying of the HPs has produced a KWH surplus now being utilized to
                      keep a second shop building quite comfortable year around, and of course
                      covering electric needs including more efficient (and QUIETER) air cond. DIY
                      installation of HPs reduces cost to perhaps 40% of turnkey.

                      As a second subject, I am curious how your ground mount has kept snow free
                      this winter? We have had a couple freezing storms here which leave ice only
                      the sun can melt loose, but my near vertical mounted panels have essentially
                      stayed clean thru it all. An array with seasonable tilt change capability can both
                      produce both optimum summer energy, and pick up a minimum of precipitation
                      in the snow months. The contrast can be seen between near vertical and best
                      summer angles in the picture, more on that in other threads. Bruce Roe

                      Feb21ice.JPG
                      Last edited by bcroe; 02-22-2021, 01:17 PM.

                      Comment


                      • #12
                        A couple items related to going all (solar) electric. Annoyed with blowing so much
                        energy outside drying clothes in winter, I bought this UNVENTED, full size electric
                        clothes dryer just available. Only a couple KWH per load, and that stays inside the
                        house, but be prepared to take twice as long and not hit as high peak temp. Moisture
                        sensing shutoff. Others here use heat pump water heaters, I think pure resistance
                        types once again are energy hogs. Bruce Roe

                        Whirlpool.JPG

                        Comment


                        • #13
                          My next electric dryer may be one of those. They are starting.to be more available in my area. Are the multiple lint filters difficult to clean?
                          9 kW solar. Driving EVs since 2012

                          Comment


                          • #14
                            Originally posted by Ampster View Post
                            My next electric dryer may be one of those. Are the multiple lint filters difficult to clean?
                            Not difficult, I use a tooth brush. Best if cleaned after every run. Bruce Roe

                            Comment


                            • #15
                              You have given me some homework to do which might take a while to complete, but a question I have is in regards to the couple comments about the very high cost of resistance heat or an electric furnace. If over the course of a year the solar panels create enough kwh to cover the needs of the entire house including an electric furnace and I have net-metering to reallocate the summer production to cover the winter usage, why doesn't an electric furnace make sense?

                              Comment

                              Working...
                              X