[danans]

> There's a lot of untapped efficiency out there.

That's especially true with houses. However, speaking as someone who has renovated their home for extreme efficiency (and now uses 75% less energy than their neighbors) the problem is that the upfront cost of efficiency - both economic and in learning curve - is still very high, at least in the US.

Unless one is willing/able to take on a big and expensive project in home building or renovation, it's hard to make big leaps in efficiency. This is compounded by the reality that the construction industry is very conservative and doesn't like doing things in new ways.

AFAICT, the only "easy" efficiency change that is close to a "no-brainer" is replacing your existing gas or electric water heater with a heat pump water heater, because it generally doesn't require replacement of an entire system, just one appliance.

The other things that make a big difference to efficiency: sealing/insulating building envelopes, installing heat pump HVAC, are much more invasive procedures.

There is a small industry of tools and contractors who specialize in those, but there's not a lot of standards or cost-efficient ways to achieve high efficiency yet. And at least in the US, high home efficiency and comfort are targeted primarily at wealthier people, and the goods/services are priced with that demographic's means in mind. Unfortunately, a few thousand wealthier people with efficient and comfortable homes does nothing for the grid or the climate.

Europe seems much further along in this area, with efficient technology and design being better captured in building codes and off the shelf technologies, and with a focus on energy efficient multi-family buildings.

[zbrozek]

My baseline electricity rate is $0.29/kWh and my baseline gas rate converts to about $0.06/kWh. Weighted for best-case efficiency that makes the the heat pump water heater 18% more expensive to run than the gas heater. Adding cognitive burden to carefully engineer the water heater's behavior and training my family to change their showering habits to leverage TOU just to maybe-break-even is a bad proposition. Plus, extrapolating the last ten years of rates, I expect electric rates will rise faster than gas rates and make the value proposition worse over time.

Edit: And of course that ignores that I have the condensing gas heater and I don't have the heat pump, so there's capex to cover as well.

[danans]

It all depends on the efficiency of your existing water heater, and your local electric rates.

I pay the same electric rates as you - $.29/kWh (PG&E). For my family of 4 using 1.024MBTU/month of heat for water, the amount of electricity consumed by the heat pump hot water heater is about 100kWh/month, which works out to or $348/year.

Furthermore, in my area, I have access to a municipal utility program that will pay me $60/year to automatically run my heat pump water heater when renewables are in over-supply, thereby functioning as a kind of capacitor for intermittent renewable supply on the grid, and lowering my water heating electricity cost to around $.25/kWh.

With my previous standard gas water heater (efficiency 65%), I was using 20 therms per month for water heating. At my current local natural gas prices of $2/therm, that would have been $480/year for hot water heating if I kept that equipment. With a condensing natural gas unit at 96% efficiency it would cost $250/year, $90/year less than the heat pump - not a huge difference.

Remember that there are a lot of old standard gas water heaters out there that are only 50-65% efficient. A heat pump water heater is very competitive to replace those.

Natural gas prices also aren't going down, and are far more subject to geo-political supply shocks, as we've seen recently, resulting in winter natural gas rates recently going as high as $2.25/therm. That's a far greater jump than electricity rates vs last year. In places like the Pacific Northwest, or Sacramento CA with clean hydro power, electricity rates are $.09 to $.18/kWh haven't budged much at all. Heat pump water heaters are even better in places like that.

Heat pump water heaters also have the ancillary benefit over natural gas of removing a major source of combustion from within your home/garage, which is better for air quality, and also removes a source of depressurization of your house's air if the water heater is contained within conditioned space.

[zbrozek]

Oh for sure there's tons of benefits if it can be made to make sense. I'm going to get one as my solar and battery capacity grow. But right now it's unimaginable to do so in PG&E territory where electricity prices rise 4-5x faster than inflation. I'd rather roll the dice on geopolitics for gas pricing.

See slide 16, which already looks quaint just a year or two later. https://autl.assembly.ca.gov/sites/autl.assembly.ca.gov/file...

[danans]

> See slide 16, which already looks quaint just a year or two later.

That's nothing.

PG&E's natural gas rates have gone up 400% since 2008 (inflation since that time has been about 30%): https://www.pge.com/tariffs/Residential.pdf

The huge jump happened in 2016, and it's stayed high since. The jump reflected increase in natural gas prices and also costs for PG&Es San Bruno pipeline explosion and the resulting higher cost of maintenance of natural gas infrastructure. It was a clear demonstration of the hidden liabilities in old natural gas distribution infrastructure.

It's interesting to note how PG&E's stock price also fared from 2016: https://www.google.com/search?q=pge+stock+price&oq=pge+stock...

which also is when they stopped paying a dividend: https://www.streetinsider.com/dividend_history.php?q=pcg

[zbrozek]

So we've paid the cost of the gas line upgrade but the cost of the electric upgrade to mitigate the fire risk is still incoming. Therefore we should expect a price shock on electricity in PG&E territory above-and-beyond the large-but-steady increases over the last eight years. And so the yawning gap will get even larger. :(

This is a shame because I strongly prefer electric everything, but not enough to make uneconomic decisions.

[danans]

> So we've paid the cost of the gas line upgrade but the cost of the electric upgrade to mitigate the fire risk is still incoming.

I don't believe we've paid anywhere near the full cost of upgrading/maintaining the gas infrastructure yet. It continues to age and will require ongoing and increasing maintenance - and expensive maintenance since lines are buried.

Furthermore as more customers switch away from natural gas, the remaining customers rates will rise to pay for the infrastructure maintenance as this paper from the Haas School of Business describes [1]:

"As Figure 4 shows, this percentage rise in bills is small when only a few customers exit the natural gas sector, but bills rise substantially if many customers exit. To understand why this relationship is non-linear, imagine that all customers but one exit, and that remaining customer must cover all of the utility’s legacy costs."

You're right that we will likely pay higher costs for electric infrastructure upgrades also - or alternatively experience more fire-avoidance PSPS events, or a bit of both.

But electricity as a medium for delivering energy offers more technological opportunities for addressing these issues and the very pressing issue of decarbonization than natural gas does going forward. Batteries and municipal microgrids are some of technologies that can help with this going forward.

1. https://haas.berkeley.edu/wp-content/uploads/WP317.pdf

[throwaway894345]

Honestly my rule of thumb with respect to climate is that private individuals’ pollution pales in comparison to upstream industry. I expect the same is true here as well-residential efficiency is probably small potatoes compared to the efficiency opportunities in industry.

[danans]

Residential is the single largest sector of electricity consumption in the United States:

https://www.statista.com/statistics/560927/us-retail-electri...

Electricity production represents 25% of GHG emissions in the US:

https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emis...

Direct residential GHG emissions (i.e. from burning natural gas) are also significant.

In total, residential energy use of all kinds accounts for 20% of US GHG emissions:

https://www.pnas.org/content/117/32/19122

[throwaway894345]

I'm not sure what if anything you're refuting here, because this all seems to support my claim that the biggest opportunities likely lie in industry.

Specifically, your bottom line ("In total, residential energy use of all kinds accounts for 20% of US GHG emissions:") is still considerably less than upstream industry, logistics, etc and especially considering the misleading framing of "US GHG emissions" which don't capture the much larger share of emissions that are outsourced via trade (i.e., America buys a lot of shit from China, India, etc and those countries' industry is even less GHG-efficient than US industry). Note that I don't mean to imply that you intended to mislead.

Maybe we're just agreeing here, and you're throwing out extra context?

[danans]

> Maybe we're just agreeing here, and you're throwing out extra context?

We can walk and chew gum at the same time. Beyond residential, private consumer choices in general - and importantly the incentives that drive them - have massive effect on upstream industrial and commercial energy uses, far greater than the 20% "residential" piece of the pie.

60% of the "transportation" sector comes from light-duty vehicles [1], which is why electrification of passenger cars is so critical.

And by the same token, we absolutely should look into the GHG footprint of imported goods from overseas or domestically produced. Carbon taxes - phased in, and with rebates to lower income quantiles - are a simple way to handle that.

1. https://www.c2es.org/content/regulating-transportation-secto...