Image Credit: Scott Gibson
More Q&A Spotlight
Lydia Segal is planning a 2,000-square foot house in Colorado (Climate Zone 6B), and aiming for “Pretty Good House” performance. Among the many questions she’s trying to answer is whether electricity or natural gas is the best choice for heating, domestic hot water, and cooking.
She’s lucky enough to have both a reliable electricity grid and easy access to natural gas in the small community where she lives. So the practicalities of delivery are not really a concern.
“We are weighing the pros and cons of gas powered vs. electric powered system for DHW [domestic hot water] and for in-floor radiant heating,” she writes in a Q&A post at Green Building Advisor. “If we set aside the issue of fossil fuel use, what are the pros and cons of each?”
That question is the topic for this Q&A Spotlight.
[Lydia Segal’s name appears as “User-6885857” in her original post. For instructions on how to change screen names, see How the GBA Site Displays Readers’ Names.]
Burning fossil fuels is always a concern
It’s not really possible to set aside the environmental issues raised by the use of fossil fuels, replies GBA senior editor Martin Holladay. Burning fossil fuels “happens to be the greatest environmental threat to life on our planet,” Holladay writes.
“Most green builders design all-electric houses,” he adds. “If their local electric company offers a program for the purchase of wind-powered electricity, they sign up with the program. If possible, they install an on-site photovoltaic (PV) system to balance their annual energy use.”
That said, natural gas has one advantage over electricity when used for heat, Holladay says. It’s often cheaper on a BTU basis.
But there are a number of disadvantages to using gas. Not only does it…
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17 Comments
Induction
An induction cooktop gives the cook the same precise control as using gas. Induction is faster and doesn't create any interior air quality issues. It's also more efficient. When our power goes out, we use our outdoor propane grille.
Andrew Bater
Andrew Bater stated:
"In times of disaster, perhaps with the exception of earthquakes and extreme flooding, natural gas infrastructure may be up and running while other above-ground electric utilities are out of service,"
The biggest natural disaster events we experience are earthquakes and extreme flooding. What else is there? Besides tornadoes and fires, which are just as deadly with natural gas since it creates leaks and explosions.
In an earthquake the biggest danger is natural gas/propane since the lines can and will separate and caused deadly and explosive leaks. Also in extreme flooding, it creates deadly leaks and explosions. The hurricanes the USA experienced last month proved that natural gas in such events is deadly. Many homes and buildings were destroyed because the gas line leaked and ignited the structure.
Gas leaks are more common than people think. Carbon Monoxide detectors are now code standard due to the CO deaths that happen yearly in the USA. Gas explosions are common and deadly. This site touches on some of those:
http://fracdallas.org/docs/pipelines.html
So in an earthquake or flooding, gas is NOT your friend but a dangerous hazard. With the power knocked out, at least your house will not explode. Gas lines leak and it doesn't take much to break a line and create a deadly leak.
So the statement by Andrew is a little misleading. Gas is dangerous in ALL natural disaster events.
Delivering propane in rural spots is a very heavy carbon footprint since the truck must haul it to the site.
Appropriate Cautions @ Peter L
Peter L's cautions are quite appropriate. My use of the word "perhaps" was inartful. Clearly with any natural or man made disaster one must examine infrastructure in the home or workplace to be sure that it is safe to operate again. That is most certainly the case after an earthquake where damage may be hidden. Making that determination may be something the average homeowner shouldn't do.
Further my comment does exhibit some northeast bias. Here the most common power failure is due to ice storms, wind shear, or critters that get fried atop poles. That happened at my house just a couple weeks ago. Our whole valley went out at 3 AM. At 5 AM I was using our LP fired stove to boil water for coffee.
That said, my comment was not without additional backup. I do have a fair amount of experience with disaster recovery, including being boots on the ground in the immediate aftermath of both '93 and '01 World Trade Center terrorist acts.
As an example, I went into New Orleans the first day the press and other critical services were allowed back in after Katrina. There my company had a facility that was irreparably water damaged, but that had a natural gas emergency generator up and running. The problem wasn't the lack of natural gas, it was that standby natural gas generators aren't rated to run days on end, they eat engine oil.
In the Northeast blackout of 2003 one of our NYC facilities quickly ran through its diesel generator supply (an unfortunate code limitation per floor in the Empire State Building), and we had to beg borrow and steal 55 gallon drums of fuel. How nice it would have been to have a natural gas generator there. Many disaster recovery centers tout such capability, for example saying things like "All Services Include UPS System and Natural Gas Backup Generator".
So in summary, one should make the determination based on some sort of risk analysis. If you live in the earthquake/fault region of California, well yes I don't think it's smart to rely on natural gas. Here in Pennsylvania you may find that natural gas availability is going to be significantly more reliable than above ground utilities.
Direct vent water heater
I'm not sure this statement above is correct: "So if you are using a gas DHW appliance, it is either power-vented, direct-vent, or sealed combustion, each of which needs electricity to work in an emergency."
There seem to be numerous direct-vent DHW appliances on the market that do not require electricity to work. The are quieter than power vented WH because they have no fan. They are sealed combustion so my understanding is they pose no risk if they are inside a tightly sealed house. The downside is there are very limited runs so they must be close to an exterior wall, and they are not terribly efficient. Martin mentioned them in this article: https://www.greenbuildingadvisor.com/blogs/dept/musings/all-about-water-heaters
Also, for many, the challenge is not maintaining services during a massive natural disaster - there are too many variables to predict what could happen and it is more than most want to prepare for (storing fuel for generator, etc.). In my area, the challenge is a few heavy storm each year that knock down overhead power lines and leave many with no electricity. Natural gas continues to flow; there has been no earthquake and no flooding. The power company prioritizes power restoration based on need (hospitals, etc) then based on how many people can be re-energized with a particular fix. If they can invest 4 hours and get power back to 1,000 homes, vs invest 2 hours and get power back to 20 homes, they will prioritize the 1,000 homes. If you happen to be one of the 20 homes, you may wait 2-5 days to get power back; yet most things are back to normal and you still need to go to work. At those times, having a water heater that works without power is a tremendous benefit...
Conservation
Throughout the entire article I don’t recall reading one word in regards to the conservation of natural resources. The question of “gas vs electric” is only applicable if gas and electricity are available, and even if they are available now doesn’t mean that they always will be. Given the comments about earthquakes and floods it becomes even more important to have systems in place that rely on neither electricity or gas.
Why not install a Tulikivi soapstone fireplace? Let that heat up your home all day and night.
http://www.tulikivi.com/en
Put in a solar hot water system. Put in all LED lighting. Assess if you really need a clothes dryer or a dishwasher. If you do, find the most energy efficient models you can. Install triple pane windows (and maybe use less of them. The very best window is worse than a lousy insulated wall).
Before you go ahead and install any heating system eliminate the waste. You’ll spend a lot less whichever method you decide to use.
Focus on Conservation
Agree with Scott...start with conservation. Minimize the needs for a heating or cooling system, and the energy needed for space heating and cooling. Use water-conserving strategies, especially for hot water usage. Use LEDs. Most of these upgrades cost little and payback is quick, plus they add resilience during outages.
To heat your home, if you have (or upgrade to) a very well insulated and airtight home, electrical or gas outages don't affect you as much. Your home interior will maintain a more comfortable temperature any time of the year, compared to the average home. A typical home interior, with sub-freezing outdoor temps mid-winter, would get very cold if there were no space heating system operating. Passivhaus or at least “Pretty Good House” insulation levels and air sealing would help keep the home more comfortable despite outages in any climate, sunny or not so sunny. Solar gains help during winter and can hurt during summer, so use south-facing windows and avoid west-facing in most situations. Passive solar heating works well for climates with sunny winters and dry summers. Downright foolish to ignore solar gains or not invest in insulation, then pay for a bigger heating and cooling system, then pay the rest of your life for gas and electric service, and suffer during outages.
For hot water... off-grid PV to heat a hot water tank directly, or passive solar batch hot water tanks, work using only solar energy and provides hot water during an electrical or gas outage. I used two passive batch hot water heaters which provided enough hot water for two people, except mid-winter first thing in the AM, with no electricity or gas (city water pressure). An active solar hot water system using pumps might work too if you had PV power available during the outage.
For PV to work during a power outage, the PV must be off-grid, or have a battery backup, or be a hybrid PV system, that cuts ties to the grid with a smart bi-modal inverter during an outage. For electricity usage for lights, charging phones or small electronics, PV would help get you through a power outage, especially if you have battery backup, but with far less than the full PV array power.
Direct vent appliances require power?
I stand corrected; really interesting that direct vent does not necessarily mean electric power is required. Their efficiency is not all that great but they manage the power and vent safety issues. Thanks for the info.
Efficiency
One thing that nobody's mentioned so far is efficiency. I don't have the answer but to take a sidestep for a moment, electric vehicles are often touted as zero emission. That's not necessarily true. EVs are zero local emission in that nothing comes out the tailpipe but one must still determine the source of the electricity - as has been mentioned. The bottom line, however, as concerns EVs is that it's much more efficient to generate electricity at an industrial level than it is in millions of individual vehicles. How does that translate into heating/cooking in a home? I don't know.
On the natural gas side, there are environmental concerns with offgassing within the home, but there are also huge environmental concerns with fracking, pipeline construction and maintenance (ask the folks in SD about that) and so on. Here the same argument applies whether one is burning natural gas in the home to cook on or whether one is burning natural gas at an industrial level to generate electricity. The grid as it stands is old, outdated and inefficient and there are line losses of electricity every day. Perhaps the best thing that can be said for natural gas is that it's arguably better than coal from an environmental perspective.
There are alternatives that are more environmentally friendly, such as solar, wind, tidal power, and more ways to keep this electricity for when it's needed - battery backup, pumped hydro, etc. There's great work being done with community level electricity generation, smart grids, micro-grids... You can even use your EV as a battery backup and/or to feed the grid when you're not using it. Of course batteries require lithium mining, wind generators can influence migration patterns and cause bird/bat deaths... Everything has a cost.
As mentioned, when it comes to heating and cooling your home the best optoon is not to have to generate anything to begin with. Proper siting, building design, insulation/ weather sealing, windows, heat pump water heaters, residential electrical backup, rooftop solar... All play a part. Why 15-20-year asphalt shingles are still legal is a good question. We have all the information we need to build smarter, better, more efficient buildings and when that becomes the minimum code requirement, we'll start to make the world a better place. What's often most absent is clinging to outmoded ideas and a lack of political will (no comment on the current US federal administration, but a lot of great work is being done on global, state and municipal levels). We all share the same planet, and I'm not just talking about humans, either. See how long you can go without breathing, and how long you can breathe without plants.
Mike.
Regarding EVs... @Mike Nelson Pedde
"...electric vehicles are often touted as zero emission. That's not necessarily true. EVs are zero local emission in that nothing comes out the tailpipe but one must still determine the source of the electricity - as has been mentioned. The bottom line, however, as concerns EVs is that it's much more efficient to generate electricity at an industrial level than it is in millions of individual vehicles. "
A few comments:
A vehicle that generates it's own electricity is a hybrid, not an EV, even if the drive train is all electric.
The energy efficiency from grid to EV to where the rubber meets the road is about 80-85%. That's much higher than an internal combustion engine's 15-25% as-used thermal efficiency.
When it comes to net thermal efficiency of the fuel-to-grid it gets more complicated. Grid sources aren't pure, different powerplants operate at higher efficiency than others, and some powerplants produce far more emissions per kwh delivered than others. A grid mix where half is nuclear & renewables and half is combined cycle gas will have a MUCH reduced annual net emissions per EV mile compared to a non-plug-in hybrid, no matter what time of day the EV is being charged.
An EV that is charged on a predominantly coal-fired grid (say West Virginia or Wyoming) has SUBSTANTIALLY higher emissions than a non-plug-in gasoline engine hybrid.
An EV owner in a deregulated electricity market who is only charging at home, and has opted for 100% renewables power is effectively nearly net zero emissions, but the model becomes very complicated, and the actual emissions may vary.
A grid that's heavily PV loaded to the point where the PV output exceeds the mid-day load on low air conditioning load days (already problem that needs addressing in some neighborhoods in Oahu) or high wind at night during low grid load (a common occurrence in the upper midwest, and parts of Texas) can charge EVs during excess renewables hours at effectively zero emissions. The technology for doing this is cheap, but the utility regulatory environment has yet to fully adapt to this new dispatchable load (the fleet of EVs plugged in to smart chargers.) But it will, probably within the lifecycle of EVs purchased today. The benefits the dispatchable load provides to the grid operator and the cost savings to other ratepayers are large- large enough to more than offset the capitalization & operation costs of the smart chargers, and is likely to be cost effective to incentivize the EV owner to always plug in with specialized rate discounts. (Third party dispatchable load aggregators of widely distributed time-insensitive loads are already in business in places where markets for those services already exist, such as the PJM grid region.)
In most of the US driving an EV has lower emissions than a hybrid today. Over the full lifecycle of an EV the amount of ever-cheaper renewables going onto the grid will be increasing (even if still dragging poor policy choice anchors), and the EV will have a lower lifecycle ownership cost to boot (!). The transition to renewables is already a couple of paces out of the starting blocks, but is only starting to hit full stride. The speed at which it can happen is speculative, but much faster than most armchair observers would guess. A decade ago non-hydro renewables accounted for less than 1% of the total grid power delivered in Iowa, now it's over 40%. EVs on smart charters would extend the amount of total renewables possible in the upper midwest before the utilities & grid operators would have to invest in storage to reduce the amount of power that would otherwise have to be curtailed, but hitting 80% renewables by 2030 in many states is now a realistic possibility (some say it's even a likelihood.) It's going to be an interesting ride!
It's not universally true that industrial scale generation is more efficient than local generation, even though it's more efficient than generating electricity with a hybrid car.
An example is large utility scale solar farms, which do not have an efficiency edge over small scale rooftop solar. At the utility scale the trend is to use a cheaper $/watt panel not higher efficiency (higher cost) panels, and just buy more panel. They gain some efficiency by buying (usually 1-axis) tracking mounts to make up the difference, because it's more cost effective at the utility scale than higher efficiency panels, at least for now. Homeowners have rooftop real-estate constraints, and usually opt for higher efficiency panels with fixed angle mounting, and are roughly comparable in efficiency to the utility scales measured from sunshine to inverter. The inverters are of comparable efficiency, but the utility scale solar farm suffers the transmission grid losses between solar farm & load, whereas with rooftop PV very little (if any) of the even the distribution grid is being used, let alone the transmission grid. The net efficiency of sunshine to load tends to be somewhat higher with the small distributed PV arrays than with solar farms by at least a little bit.
Another example would be heat & power cogenerators, which also works at comparable efficiency at the micro-scale. A ~kilowatt natural gas fired Honda with a buffer tank for storing the heat operates at the same or higher thermal efficiency of many natural gas fired 100 kilowatt industrial cogenerators. A decade ago it was possible to buy the tiny Hondas married to a home heating system in my area (one of the guys in my office is heating his house & hot water with one, net metered to the utility), but the systems they were married to were sized for heat loads many times larger than a Pretty Good House, and it was never made available in the US as a standalone.
@ Mike
"...electric vehicles are often touted as zero emission. That's not necessarily true. EVs are zero local emission in that nothing comes out the tailpipe but one must still determine the source of the electricity."
Very good point. EVs can be used as electrical storage devices as well as very efficient transportation. However, if they are used for their electrical storage capacity they are very dumb things - they can be fed with electricity from a renewable resource or something that is not at all. The current renewable energy resources in the USA only form 15% of total electricity use. This should not be forgotten. See here: https://www.eia.gov/energyexplained/index.cfm?page=electricity_in_the_united_states
Also, the way the current lithium ion batteries perform is far from ideal. They will need to be replaced eventually at a not insignificant cost. In that sense they are not a very green solution. See here: https://singularityhub.com/2017/09/21/to-achieve-100-renewable-energy-we-need-way-better-batteries/amp/
We're happy w/a gas cooktop and electric everything else.
Our home is what I would call a "pretty good" home. It's a Unity home, and has but one energy "sin", and that's our gas (propane) cooktop. With a well made, well insulated, well sealed home, we've not noticed the energy cost of the vented hood and actuated make-up vent. I'm sure the impact is real, but we're very happy with the performance of the home. Most times when we're cooking, we're only using one or two burners, so we don't even bother turning the hood on, but when we can, or have three or more burners going we use the hood.
CO2 levels and range hood fans
As mentioned above I do run an LP range in our home. I operate the range hood fan and open a compensating window a crack each time I use the range. The house was last measured at .9 ACH.
I also monitor CO2 levels in the house; I have a commercial Honeywell CO2 monitor sensing the discharge of my HRV. I use the Honeywell monitor to switch the HRV fans to high once the indoor CO2 concentration reaches 700 ppm.
Interestingly, even though the range hood fan will be screaming, and fresh air will be flowing into the kitchen area dispersing cooking smells, quite often the indoor CO2 levels in the house will climb anyway, particularly if I use the oven. It's like CO2 doesn't follow the "rules".
Just an observation. And one that I know runs counter to my "pro" natural gas / LP argument above.
Gas cooking and indoor pollution
Range hoods aren't all that effective, especially if located over an island (or of course if turned off due to noise or to reduce wintertime heat loss).
This article notes that cooking with natural gas, and not using a range hood, often increases pollutants beyond the range considered safe by the authors. It also notes that cooking itself releases some pollutants.
https://ehp.niehs.nih.gov/122-a27/
Updates from the homeowner
I was amazed to see my name and question as the topic of this Q and A spotlight. A few details and follow ups since I posted the question initially a few weeks ago,
We are building a 2000 sq ft (450 attached garage) one story in building zone 6B, 7000 hDD, elevation 7100. The R values and construction are as follows: slab on grade R15, Walls R30 with cellulose insulation 2 x 6 with 24 OC with zip and roof at a 1:12 pitch standing seam with cellulose insulation R 50.
House orientation is pure South with NO visual obstruction in the north and south orientations and only one story homes to the east and west.
Windows: fiberglass framed, U < 0.25, SHGC mid range or depending on orientation. brand selection is a challenge as the local retailer does not sell what we would like, and we are balancing future service and brand preference.
Mechanicals: Heating will be with in floor radiant. Yes I agree that mini splits are likely better, but my spouse is prone to allergies and less blowing air the better. We currently rent a place a mile from our future home that uses it and I love the quiet of the system. It will be heated by an electric system stored inside the mechanical room that will be inside the garage that will NOT have infloor heating. The rest of the DHW needs will also be supplied by an electric system that is separate for the space heating system but also in the same mechanical room. Ventilation will be by three bathroom exhaust on times and demand and the kitchen hood.
Note much of this set up was suggested by the the architect and by an engineer who specializes in energy efficient homes. We realize that heat pumps are more efficient, but we will not be in the house all the time and placing them outside is of some concern.
Kitchen - oven wall mounted electric. Stove top is being dual plumbed for natural gas and electric. Yes I know. It should just be electric. I purchased a single portable induction cook-top to try it. And would be willing to go with that but, see next paragraph.
Fireplace: ok GBA is not happy with this from what I have read on this site and others. But my spouse wants a fireplace. This is for some occasional 'fast' heat addition during the winter and back up for grid loss electricity.
PV panels - yes will be installed during construction. The local wonderful company is figuring about a 6kwh system. We live in the city of 5000 where you must be grid tied and there is net metering.
Other details, Lights , all LED, ceiling fans in great room and master bedroom, low flow commodes, showers etc, invisible universal design with essentially no thresholds, a min. of 3 foot doors, easy use handles, roll in shower in master bath etc.
Likely I am forgetting some important detail, but we are off to see to about frivolous details like shower tiles and whatnot.
Any suggestions are appreciated, be kind as this is NOT my field of expertise, and using terms like heat pumps and 24 OC were total unknowns to be me 3 months ago. We did change a number of things that we learned from this site.
Lydia
Overly pessimistic @ Eric Habegger
"The current renewable energy resources in the USA only form 15% of total electricity use. This should not be forgotten."
"Also, the way the current lithium ion batteries perform is far from ideal. They will need to be replaced eventually at a not insignificant cost. In that sense they are not a very green solution."
That "...not insignificant cost..." is going down rapidly year-on-year, and the performance is incrementally improving year-on-year.
And at end of life as an EV battery there is still VERY significant residual life (and value) as a home storage battery. California's Independent Grid Operator (CAISO) is even counting on both EVs on smart chargers and a growing supply of EV batteries as enablers of higher penetration of renewables for their 2030 renewables target planning. See their very short-form (25 page) discussion of 2030 planning and some questions needing resolution here:
http://www.caiso.com/Documents/Electricity2030-TrendsandTasksfortheComingYears.pdf
So how un-green is that, really? At typical driving patterns an EV that hit's the road will be up for new battery sometime around 2025, and the market for the second-life battery should be much better developed by then.
At end of life as a home or business storage battery lithium ion batteries are fairly recyclable, assuming lithium ion hasn't already been pushed out of the market by cheaper-better batteries.
Meanwhile there is regional planning for DC fast charging networks in progress, which will themselves become enablers of higher penetration of renewables, since they will all need to have substantial battery storage to really serve the fast-charging function.
http://energy.utah.gov/governors-sign-mou-plan-regional-electric-vehicle-corridor-west/
Tesla makes money on their network of DC fast chargers selling ancillary services into the wholesale electricity markets (even when making negative margin on their car sales) due to the flexibility of their stationary battery packs that run the DC fast chargers. Others will do the same.
Local slower chargers are also grid stabilizing assets enabling higher penetration of renewables too:
http://www.utilitydive.com/news/electric-vehicles-can-be-grid-assets-or-liabilities-how-utilities-plan-wil/442661/
Viewing it all through the lens of the state of renewables penetration of the grid energy market circa 2016 is distorting, and completely misses the point. EVs aren't a net- carbon emissions problem (compared to a non plug-in hybrid) NOW except in some parts of the US grid, and even there it will only for the short term. Now that both wind and PV have crossed levelized cost thresholds making them the CHEAPEST new generation, the transition to deeper penetration of renewables is going to accelerate, even without federal policy tailwinds. The rate at which the grid can get greener is enhanced by more EVs, a very real part of the SOLUTION to creating low carbon grid.
Unpowered direct vent gas water heater? Be careful. Our most recent build has a tankless gas water heater that will not operate with the vent hood on. MUA installed per code and commissioned by HERS rater. The gas water heater's internal fan is not strong enough to overpower the vent hood depressurization, so how is one without a fan going to fare?
Gas fiends are increasingly recognizing superiority of induction. On top of fast and accurate controls, they are easiest to clean. Better indoor air quality is also thanks to spills that meet a cooler glass surface compared to hot grates. Less smoke and burned food.
The unpowered type have a "closed loop" intake and exhaust that is not affected by negative pressure in the house - so there are no outside forces to overcome.
Also, you can tie your vent hood (assume you are referring to a kitchen exhaust) to a makeup air system that has a damper that opens when you turn on the hood to balance out the house.
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