Home Building Questions - Propane - All electric - Fireplace

[LittleBittyBigJohn]

Since you're just beginning this process, have you also considered an integrated safe-room, storm shelter, refuge in preparation for those tornadoes?

Yes, we will have a safe room.

 

[Carl_NH]

Bad numbers. A heat pump is 300% efficient.

Larry - These numbers came from PSU calculator - the only aspect you would change are the cost of energy and efficiency of your systems . As I understand this, the 11,945 BTU per KWH vs 3412 BTU for resistance heating that is the 3.5 times the BTU per KWH or 350%.

Where is the math wrong or how would you derive the BTU per KWH input for heat pumps?

 

[ponytug]

Larry - These numbers came from PSU calculator - the only aspect you would change are the cost of energy and efficiency of your systems . As I understand this, the 11,945 BTU per KWH vs 3412 BTU for resistance heating that is the 3.5 times the BTU per KWH or 350%.

Where is the math wrong or how would you derive the BTU per KWH input for heat pumps?

Like @Larry Caldwell, I was thrown off initially at the 100% number, but then I realized that the BTU/kW had been tweaked. I think that the math in the sheet is fine as far as it goes, but can I suggest a tweak?

My suggestion would be to add a COP number to the spreadsheet, and then multiply the BTU/kWh resistance heat (3412) to get the heat pump number. The sheet came preset for 3.5, which is close, but some heat pumps do break 4, and some do worse. (Or multiply the efficiency)

All the best,

Peter

 

[CoolTech]

I too am in the process of building our final home. We're in Southern California and we have a lot of sunlight - so solar energy is much more abundant than other parts of the Country. As such, the new house will be all electric - albeit with the best energy-efficient appliances that we can reasonably get. The AC units are very high SEER (efficiency) rating and use heat pumps for the heat but complemented with heating elements as well (because heat pumps are so good in temps below 40F). Water heater is a heat pump unit as well. Back in 2013 I installed solar on our previous house and California had an attractive "Net Energy Metering" (NEM 1.0) program at that time. Essentially every excess kW you generated went back to the grid and counted as a credit. In the sunny but not hot months of Jan-May/June, we would accumulate a substantial amount of credits. Then, in the AC months of July-September, we would use those credits as these were typically the only months that we used more than we generated. By 2020 when my son installed solar on his house, NEM 2.0 had been introduced. Long story short, credits were counted by time-of-use and so when you stored credits and then pulled them back out again, it wasn't 1 for 1.... but more like 80 -85%. Still a good program. However, 3-weeks ago the Public Utilities Commission voted and adopted NEM 3.0. (NEM 2.0 customers get a 20-year grandfather.) New solar customers after April 15, 2023 have only NEM 3.0 and, in brief, it is more or less like getting 2 credits back for every 10 put in. (The utilities argued that they buy energy at about $.08/kW and then resell it to consumers for a minimum (lowest tier) of $.24/kW, so why should they have to pay/credit consumers at $.24kW? The PUC agreed with them and now consumers will only get ~$.08/kW credit.

Long story short is that for the first time in CA new solar customers MUST consider batteries. Essentially the utility companies were acting like battery banks - but no more. So, now I am in process of going back to the drawing board to try and model the size/capacity of the batteries I will need to "buffer" consumption for my new house which is now ~50% completed.

 

[Carl_NH]

My suggestion would be to add a COP number to the spreadsheet, and then multiply the BTU/kWh resistance heat (3412) to get the heat pump number. The sheet came preset for 3.5, which is close, but some heat pumps do break 4, and some do worse. (Or multiply the efficiency)

Hi Peter,

It's a spreadsheet so once you copy and paste into excel and get the formula's set, you can adjust and add any number of calculations. The other issue is the COP changes with air source heat pumps, so manufacturers set their HSPF based on the heating seasons average temperature.

For example, as temperature declines in air source heat pumps, their efficiency drops especially near 5*F and below the COP changes. There is the COP, and also HSPF which are similar you can convert HSPF to COP by multiplying the HSPF number by 0.293. Our Mitsubishi Hyper heat 9K have an HSPF of 13.5 which is equal to a seasonal average COP of 3.95. There are some units with a higher COP/HSPF as you indicated.

The actual COP is a factor of outdoor temperature. The COP of the Mitsubishi 9K hyper heat mentioned above at 47*F is 4.26, at 17*F is 3.37, and at 5"F 3.1.

Bottom line, a COP of 3 (or 300% output for 1 KWH input) is a pretty average number to use. YMMV based on the climate you live in.

 

[newbury]

I have been charged $.30+ a kilowatt a time or two. I didn't like that much either.

That's Texas, correct?
Our electric rates in Mississippi (TVA co-op) preCovid were about 9.5 cents/KW, now they climbed up to 10.3 cents, so it greatly depends on your utility company. I suspect central Arkansas to be about 15 cents/KW or less.

Wife and I can shower back to back and pretty much be ok.

That's REAL good

Now for the OP -
Your at about the same climate/latitude as we are in Fulton, Mississippi
You definitely need 2 or more sources for safety and security but you also need to analyze your requirements.
For example
I grew up in northern Vermont and remember many winters with 40 below, where °C meets °F, and weeks of never getting above 0°F. My wife grew up in Fulton, Mississippi where the absolute record low was ‑12 °F since she was born. And since we starting moving back here in 2010 I can't remember a winter with one week it stayed below freezing.
At this writing the heat pump is on and keeping the house at 60°F, our heat bills are rarely over $100. We wear flannel shirts when needed.
We also have a LPG gas flame fireplace which we've used a few times since 2012 during really cold spells.
But we are in a house built for 1970 TVA rates which I think were less than 4 cents/KWH.
If you can change the design of your house slightly (sunrooms etc.) you can probably minimize your heating and cooling.

 

[dmccarty]

When we designed and built our house, we put in a hearth to hold a wood burning stove. A fire place or stove can heat a house but the key is the combustion air. We have a six inch PVC pipe that is behind the stove and goes outside. When the stove is running you can feel the air being pulled into the house and fed to the stove. A family member built a house with a fireplace that was the center of the house and made from brick and stone. He had a pipe running under the slab that terminated in front of the fireplace to supply combustion air. Like our stove, when the fireplace was in use, you could feel the air from the pipe rushing out of the register. He heated his house most of the time with that fireplace. The key is to have combustion air supplied from outside of the house, other wise, heated air from the house goes up the chimney.

Regarding water heaters. We bought an 80 gallon unit that was very energy efficient and have never run out of hot water. I think now you have to have a heat pump water heater for that size. An advantage of a larger water heater, if you are on a well, is that you have water if you really need it....

We have low flow shower heads and reducing water usage is more important than having a large water heater. We use very little water in the shower and the low flow shower heads work just fine. Can't stand the wastefulness of some of these shower heads...

 

[dmccarty]

...

Long story short is that for the first time in CA new solar customers MUST consider batteries. Essentially the utility companies were acting like battery banks - but no more. So, now I am in process of going back to the drawing board to try and model the size/capacity of the batteries I will need to "buffer" consumption for my new house which is now ~50% completed.

Take a look at LiFePo batteries, chargers and inverters from Victron and Mastervolt. They sell systems that are used by boats, RV and homes to supply power. Some people are building there own LiFePo batteries but I that is not for me.

Using batteries to power a house is going to be limited and HVAC is not going to be able to run unless one has a monster and expensive battery bank. The HVAC won't run for long if it can run at all. Using large appliances might be possible, with the exception of an electric clothes dryer, and not sure how much power the new heat pump water heaters draw.

I would NOT put a lithium battery system on/in my house due to the fire risk. LiFePo is almost impossible to get to burn and is safer. LiFePo is a lithium based battery but there are differences in the different battery chemestries.

 

[alexinPA]

We are getting close to building a house in a semi-rural area. Feels like the country but close to town. The area has water, electric, and internet. But no natural gas or sewer. We are currently in an all electric house trailer on the property, temporarily until we get the house built.

The questions this time revolve around not being able to decide whether we should go all electric or get a propane tank. If going with propane, what all should we use it for. We don't typically have many electrical interruptions except for the occasional tornado.... Winters are not cold cold, nights typically hover around the freezing mark. Just a little under or over. We don't get a lot of days where the high stays below freezing. We get 3-4 really cold snaps per winter usually. Just a few days where it stays below freezing. Some winters we get 2-3 snow events and some winters none. If we did get propane I would prefer a buried tank but they are not exactly cheap. I don't think the actual propane is all that cheap either. Not sure if it will save money compared to electric or cost more. I'm beginning to think that I don't really want to deal with propane at all but I don't want to take it off the table if it's the better way to go.

We are building in a fireplace. Like a lot of people we don't have a lot of margin at this point in our lives, so I don't think a traditional wood burning fireplace would get used much. We are gone a lot or otherwise just don't stay home all day to make use of a fire that takes a long time to build or burn out. Not to mention we wouldn't be able to harvest our own wood. So I either want to put in gas logs or a pellet insert. Either one I would like for heat and to be able to see the fire.

Water heating is another question. The houses I have lived in with gas water heaters I never had an issue running out of hot water, I have run out many times with the electric ones. We are building a double shower in the master so I know we will use more hot water than usual. What is the solution?

I have never cooked on gas so at this point that's moot. Electric either way.

Heating furnace... The gas furnaces I have had in the past have been awesome. However, the electric one that is in our 10 year old trailer house has done a phenomenal job. Even in the cold snap just before Christmas, where nights got down to zero, it stayed 70 degrees all night. I am not scared of electric heat any more. I have heard of electric units with propane emergency strips. I'm curious if that is worth checking into. Also, I think a pellet insert in the fireplace providing additional heat would make me even less scared of electric heat.

I do think I'm going to have the house wired for a generator. Even if we don't get the automatic whole house generator, we would still be able to plug in a decent size one to run the pellet stove, refrigerators, freezers, etc. Then there's the gasoline vs propane question there too... So many decisions.

Look into dual fuel furnace. They come electric+wood, oil+wood and propane+wood. Ive been using propane/wood for 20 years. Using 50-70 gallons of propane for a season, the rest is wood. Works great

 

[CoolTech]

I would NOT put a lithium battery system on/in my house due to the fire risk. LiFePo is almost impossible to get to burn and is safer. LiFePo is a lithium based battery but there are differences in the different battery chemestries.

Definitely will use LiFePo - almost all storage is that way now anyway. If I don't use Enphase batteries, then I will likely use a an easily extendable rack-mounted battery system - either 30 or 60kW (still planning). But, yes, the batteries WILL be able to run the AC units. These new, variable speed, AC systems have the ability to run at a very low power level. Rather than a traditional unit that runs and then waits for a 4-5 degree temperature differential and runs again, these units will run almost continuously, albeit at a very reduced speed/power consumption. In the summer with ample sunlight I do not think I will have a problem to run the AC's through the night. Right now I am more concerned about the winter months (if there even is such a thing in SoCal) where you may not have full sunny days but you need to run the heater - perhaps especially in the mornings when everyone is waking up. I'm doing some modeling right now based on my son's house and his actual generation/consumption data from the last two years... and then I can just scale it for the size of my house and number of panels.

The one bit of planning I did right is that along with the house build, we're also building a 85 x 42' shop. I set the shop 90-dgrees from the house so that one entire roof half of the shop is pointed South - ideal for solar. We will be installing 60 panels on this roof.