[caminante]

I'm jealous of the learning and hobby project.

Though, the returns are (edit: "not great") if the figures above INCLUDE net metering revenues.

    Heatpump = Negative IRR until y8
    Solar = Negative IRR until y16
    Heatpump + Solar = 0 NPV through y25 | 8% discount rate

[thelastgallon]

I'm jealous of your financial learnings. However, your model is not accurate as it doesn't factor in the 4 degree improvement in comfort and indoor pollution from propane furnaces: Propane furnaces can cause indoor pollution through the release of pollutants like carbon monoxide (CO), nitrogen dioxide (\(NO_{2}\)), and benzene, which are byproducts of combustion.

It also doesn't include the negative externalities because of tragedy of commons. Sadly, these kind of flawed 'financial' calculations are widespread.

What is inspiring from the OPs comment is that this is doable in harsh Canadian winters with negligible solar and it breaks even. Most of the world is living in significantly more sunshine, so it should work out a lot better financially for >99% of the population.

[antongribok]

I've lived most of my adult life in houses with forced air furnaces (albeit powered via natural gas, not propane), and what you are saying is inaccurate regarding indoor air pollution unless your furnace is in need of immediate replacement.

A modern furnace works via a heat exchanger, where the combustion produced pollutants never mix with the indoor air being pushed through. All pollutants are expelled outside via a property functioning chimney. This is one reason why you should have the furnace (and chimney function) inspected annually. Aging heat exchangers will show hotspots before there is a possibility of air being mixed, giving plenty of time to plan for a replacement. Of course there is a possibility of failure, which is why you should have a carbon monoxide detector.

[caminante]

I agree it's important to watch for these things.

For externalities or immediate health benefits, heatpumps are pretty defensible. However, solar isn't a saint. Rare earth/mineral mining is hazardous plus only a fraction of solar panels are getting recycled properly.

> this is doable in harsh Canadian winters with negligible solar and it breaks even

It's doable alright. OP got subsidies (See comment re: risk free loan and grants). Talk about externalities, this is definitely wealth transfer.

[thelastgallon]

Yes, lets talk about subsidies. Fossil fuels have had and continue to have the most subsidies. Fossil Fuel Subsidies Surged to Record $7 Trillion/year: https://www.imf.org/en/Blogs/Articles/2023/08/24/fossil-fuel...

The wealth transfer you are alluding to, it is from the poor (everyone) to the rich (fossil fuel billionaires), isn't it?

[caminante]

Please avoid unwarranted "whataboutism."

[vanviegen]

This is not whataboutism though. It's comparing two alternatives on a relevant aspect.

[caminante]

LOL.

Can you please share your definition of "whataboutism?" And explain how bringing up a single alternative (plus flaw) is addressing the critique and NOT changing the subject?

[thelastgallon]

You brought up subsidies. I updated your understanding of subsidies. What is this whataboutism you are talking about?

[caminante]

> I updated your understanding of subsidies.

Adults don't talk like this. The parent shared they would be far less likely to have moved forward without the subsidies. Now, you implied that someone (me) pointing out a tradeoff of solar subsidies must be non-critical of O&G subsidies, yet you provided no proof that I wasn't ALSO critical of O&G subsidies.

Meanwhile, I would love to learn more about the financials of your non-profit, ChargeFoundation.org that has mailing to a residence in Austin, TX. I'm not seeing any 990s.[0] Can you please post your foundation's financial reports on your site?

[0] https://app.candid.org/profile/15315388/charge-foundation-93...

[zbentley]

I hope we can agree that fossil fuel consumption is something to be avoided. Subsidies are an effective means of incentivizing people to avoid fossil fuels.

If you believe the externalities of solar are a problem, what do you propose to do instead? Should we subsidize some other alternative? Redirect resources from oil to nuclear? Other?

[caminante]

>avoided [entirely?]

You're making different/absolutist arguments. Even the most ardent electrification proponents agree that you can't replace downstream chemicals/materials.

As for subsidies, you're thinking too narrow if you feel it necessary to only spend limited government budget on energy to improve lives.

[zbentley]

At no point did I make an absolutist claim. If I meant “fossil fuel use should be eliminated”, I would have used those words. Do you agree that it should be avoided and/or curtailed? If not, there is little point in continuing to discuss here, as we will likely never see eye-to-eye on this.

> you're thinking too narrow if you feel it necessary to only spend limited government budget on energy to improve lives.

I also did not use the word “only”. Governments are quite capable of doing more than one thing at once. Should governments not consider spending money on energy to improve lives?

[thelastgallon]

> As for subsidies, you're thinking too narrow if you feel it necessary to only spend limited government budget on energy to improve lives.

But, its perfectly okay for govt to spend on fossil fuel subsidies? You draw the line when the subsidies are for solar, heatpumps, etc?

[thelastgallon]

> However, solar isn't a saint. Rare earth/mineral mining is hazardous

Solar cells are made of silicon, not rare earths.

For solar, you need to mine ONCE for 25 - 50 years. Fossil fuels are burnt every second continuously. Perhaps you can do the math if its not obvious?

[bluGill]

Indoor propane furnaces exhaust outdoors in most cases. Space heaters that exhaust indoors are rare - more used for garrage heat than house. If you use them of course actount for it, but most are not.

[Scene_Cast2]

Theoretically yes, in practice no. There is (according to my sensors) a fairly large CO2 increase inside a room when a modern furnace (with external exhaust) is running. I've confirmed this with several units (all made in the last 10 years), and it's not that the windows are closed - when the furnace turns off, the CO2 drops. And it's not that the exhaust is placed in a bad spot either.

[caminante]

> There is (according to my sensors) a fairly large CO2 increase inside a room when a modern furnace

If this is happening, then you shouldn't be using that furnace/room!

Something beyond the furnace is not configured right.

[thelastgallon]

Yes, fossil fuels are the best to keep pollution away, just need to installed perfectly, configured and maintained regularly, monitored to make sure everything is running correctly, and have additional properties lying around vacant just in case there are leaks, misconfigurations, poor installation, etc. But we must use fossil fuels, there are no other options!

[PaulDavisThe1st]

Could also just be the furnace. Incomplete combustion conditions can give rise to the symptoms mentioned here.

[caminante]

I doubt it's the furnace, unless there's a serial defect/recall.

The problem is likely "between the keyboard and the chair." ;-)

[Shog9]

Your control for this test should be (and maybe was, you don't say) running the furnace circulation fan without running the burner. CO2 levels are unlikely to be uniform throughout a building, and thus mixing will change (raise, lower) the CO2 levels depending on where you're measuring.

[Reason077]

Looks pretty good to me over 25 years. Not many safe/guaranteed investments that will reliably return 8% these days. And as utility rates will no doubt rise over time, savings in future years will be greater.

[glxxyz]

Yes the people selling solar systems all factor in aggressive future electricity increases, it's best to also see how it looks with more conservative rate increases. By my calculation in a reply above with the interest free solar loan it's an 8% return over 14.3 years.

[thelastgallon]

Residential electricity rates have risen fast across the US—more than 30 percent on average since 2020 and almost double the rate of inflation: https://www.wired.com/story/power-bills-in-the-us-are-soarin...

[Spivak]

It will be interesting to see if this will make natural gas a more attractive source of residential heating as the price has remained relatively stable over the past 20 years.

The push for electrification seems like it relies on us metaphorically drowning in excess cheap electricity and want somewhere for it to go but right now the opposite it happening.

[ssuds]

>The price has remained relatively stable over the past 20 years

Not really, natural gas has immense exposure to geopolitics and the commodity markets: https://www.iea.org/commentaries/what-drives-natural-gas-pri...

There’s also the argument to be made (this has manifested in other countries) that as gas usage wanes and more homes electrify, nat gas costs will increase as the infrastructure costs are spread among fewer and fewer people

[Marsymars]

> There’s also the argument to be made (this has manifested in other countries) that as gas usage wanes and more homes electrify, nat gas costs will increase as the infrastructure costs are spread among fewer and fewer people

This has kinda wonky incentives though - if your fixed costs for gas are high but your marginal costs remain low and for whatever logistical reasons you can't cut the gas connection entirely, then your motivations are to move as much of your heating load over to gas as possible.

[caminante]

I skimmed the article (so forgive me if I'm off.) It appears to reference non-US markets and the parent was assuming US (my assumption).

AFAIK, the US has a mid-long outlook of gas oversupply. EU's market is broken and has 3x the price (c.f. Henry Hub v. TTF). I haven't seen any major forecasters predict reaching parity anytime soon. Hence, LNG export projects keep getting (over-)built to chase the arbitrage.

[bluGill]

Very regional though - my rates have not gone up.

[thelastgallon]

Electricity prices are going up nearly everywhere. Bitcoin and AI are a wealth transfer from everyone to the crypto/AI folks.

Wholesale electricity costs as much as 267% more than it did five years ago in areas near data centers. That's being passed on to customers: https://www.bloomberg.com/graphics/2025-ai-data-centers-elec...

[geysersam]

That doesn't make any sense. Bitcoin miners get wealth from people buying Bitcoin, not from electricity customers. Same for AI. It's a wealth transfer from electricity customers to electricity producers if anything.

Most likely most of the increase is just temporary though. Electricity supply will increase to meet the sudden and unpredictable increase in demand.

[conradev]

I got solar for my parents in 2021 and the price increases were pretty aggressive recently: https://fred.stlouisfed.org/series/APU000072610

[Ekaros]

Which to me is funny, when the electricity prices will clearly not rise when there is solar energy production from said panels. But might in other times.

[glxxyz]

I think the argument is that on average people are buying heat pumps and EVs faster they are installing solar panels but it’s not completely convincing though, power stations can be added.

Further north where I am solar can only ever be a small component of total electricity generation due to the dark snowy cloudy winter months with close to zero solar generation for weeks on end.

[adrianN]

Batteries for load shifting a few hours mitigate that quite a bit and are getting cheaper fast.

[glxxyz]

The issue for me with batteries is that in the summer I can produce in a day much more than I can use, and in winter I consume a lot and barely produce anything. This is where net metering steps in- I can ‘store’ all of my excess summer consumption in the grid in summer and get credit for it in winter.

A cheaper smaller system right sized for summer consumption with a battery would have my second best option, but for me never showed any potential payback due to the fixed costs of installation and the extra battery costs.

[adrianN]

Net metering is of course nice for consumers but it’s not sustainable for the grid operators.

[brianwawok]

I have never had a prime time surcharge so I can’t do that trick. Think it’s because my baseload here is nuclear.

[glxxyz]

Yes the figures are my approximate bills so include net metering revenues.

You're right about the 8 year negative IRR for the heatpump, although I'm being very conservative about propane costs, it's likely much shorter. I was pretty conservative about the solar savings too, I generally go for the worst case in these estimates.

Your overall NPV calculation seems a bit off. It's ~21 years to zero NPV at 8% discount rate, spending $80 up front to save $8/year. Factoring in the 10 year interest free government solar loan makes it more like 14 years. My working:

    =nper(8%, -8, 80)
    20.9

    =nper(8%, -8, pv(8%, 10, -4)+40)
    14.3

The solar system is fun to tinker with and should pay off 'eventually', it's not a no brainer of a decision like the heatpump though.

[caminante]

> Your overall NPV calculation seems a bit off.

Correct. It's 21y. I missed $500 from a reading error and was assuming $7.5k/y (not $8k/y).

edit: I see your mention of the grant, too. Combined, that's cutting the NPV=0 point in half from 21y to ~12y. Good job.