Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

What a year of solar and batteries saved us in 2025

scotthelme.co.uk

Post reply on HN
Print view View original

101–110 of 368 posts

Re: What a year of solar and batteries saved us in 2025

#101

Post by dymk »

latchkey wrote: post #85
vasco wrote: post #51

Earlier quoted context omitted.

Almost all simulations I've done across 3 countries with 3 different payback models for selling back to grid (one of the three doesn’t allow selling back almost anything above your consumption), I could never make investing in Solar not being a gamble. You really need to gamble on odds of replacing equipment being very low for it to make sense. And in practice most people I anecdotally know that run it, after 5-7 yea…

Having power when your entire neighborhood is off, priceless. [edit: yes, I assume you also get batteries, I know that solar alone doesn't magically power your house.]

99% of systems are grid tie, so unless you’re spending another $7k for an ATS and associated infrastructure or you’re 100% off grid, your power still goes off.

Re: What a year of solar and batteries saved us in 2025

#102

Post by ortusdux »

mbesto wrote: post #52

It's wild how overpriced Tesla Powerwalls are. 16 kWh battery with all of the UL supported listings etc = $3300 [0] 13.5 kWh Tesla Powerwall is $12k~$15k You would get your return way back quicker. [0] - https://www.ruixubattery.com/product-page/lithi2-16-battery-... EDIT: As others have pointed out, powerwalls have inverters built in so it's not totally apples to apples. You can get a beefy inverter for $5k and it's…

IIRC, the original idea was that they would pull older batteries from circulation when their capacities dipped, and then repurpose them as powerwalls, an application where weight is irrelevant.

This was back when they expected the batteries to plateau at ~80% capacity after a few years, and they had battery swapping on the roadmap, so they needed to plan for a future where they had a steady supply of batteries that car customers did not want.

The idea took hold, but the batteries lasted longer and swapping didn't pan out, so now they are competing with themselves for battery supply.

Re: What a year of solar and batteries saved us in 2025

#103

Post by O5vYtytb »

mbesto wrote: post #52

It's wild how overpriced Tesla Powerwalls are. 16 kWh battery with all of the UL supported listings etc = $3300 [0] 13.5 kWh Tesla Powerwall is $12k~$15k You would get your return way back quicker. [0] - https://www.ruixubattery.com/product-page/lithi2-16-battery-... EDIT: As others have pointed out, powerwalls have inverters built in so it's not totally apples to apples. You can get a beefy inverter for $5k and it's…

That's not really apples-to-apples comparison. The Tesla batteries are AC coupled so they work with an (AC coupled) microinverter array. For a DC coupled battery you have to have a hybrid inverter and DC couple the batteries.

Your point that they are overpriced still stands though.

Re: What a year of solar and batteries saved us in 2025

#104

Post by kccqzy »

lostlogin wrote: post #19
cptcobalt wrote: post #14

Earlier quoted context omitted.

Not all homes are made equal: different appliances & electronics from different vintages, etc. I have 2 EVs (Tesla and BMW), an electric oven, and a homelab rack (but no HVAC), and my usage was 34.4 MWh last year — with 100% from Solar and Powerwall.

That’s an awful lot of power. I’m waiting on a quote for an hvac that uses its waste heat for the home hot water. Im irritated that I’m cooling the house, pushing out hot air, and heating water at the same time.

You just need an air source heat pump water heater and install the water heater next right to the outdoor unit for the HVAC.

Re: What a year of solar and batteries saved us in 2025

#105

Post by dymk »

systemtest wrote: post #98
dlcarrier wrote: post #67

Where I am in California, there's a $30+/mo charge to connect to the grid, and the largest savings from a battery was being able to disconnect from the grid. There's lots of time I have excess power generation when I could give to the power grid, if I were connected, but I would have to pay extra to do so, so the potential goes unused.

Is delivering back to the grid economical in California? Where I'm from people disconnect solar panels on sunny days because it costs them money to return to the grid.

PG&E does net metering, but even at a sub 1:1 rate past your net usage it does not make sense that it costs more to send energy back to the grid

Re: What a year of solar and batteries saved us in 2025

#106

Post by coryrc »

systemtest wrote: post #98
dlcarrier wrote: post #67

Where I am in California, there's a $30+/mo charge to connect to the grid, and the largest savings from a battery was being able to disconnect from the grid. There's lots of time I have excess power generation when I could give to the power grid, if I were connected, but I would have to pay extra to do so, so the potential goes unused.

Is delivering back to the grid economical in California? Where I'm from people disconnect solar panels on sunny days because it costs them money to return to the grid.

The worst that happens is you get paid back at the wholesale rate (from your bill, not live market price) instead of discounting kwh-per-kwh.

Re: What a year of solar and batteries saved us in 2025

#107

Post by scarecrowbob »

dns_snek wrote: post #92
mbesto wrote: post #52

It's wild how overpriced Tesla Powerwalls are. 16 kWh battery with all of the UL supported listings etc = $3300 [0] 13.5 kWh Tesla Powerwall is $12k~$15k You would get your return way back quicker. [0] - https://www.ruixubattery.com/product-page/lithi2-16-battery-... EDIT: As others have pointed out, powerwalls have inverters built in so it's not totally apples to apples. You can get a beefy inverter for $5k and it's…

You're comparing the cost of a battery with a full system. That 16 kWh battery requires a ~$3000 inverter to go along with it.

Well, the math still maths, right?

I am writing this off grid, using about 15kwh of batteries and a $1200 (6kw) inverter. My entire system puls panels and racking those panels, plus wiring some un-powered shacks was about $10k, though I did the work myself (which would probably hae been another 3-5k if I could have found someone to do it.

Re: What a year of solar and batteries saved us in 2025

#108

Post by n8m8 »

systemtest wrote: post #90
boringg wrote: post #34

9-11 year payback isn't bad based on the projections. You could probably goose it a bit with inflation of electrical prices (depends on how the electrical policies change and what they pass through). I'll also add theres some O&M coming down the line. Inverters @ year 10, small maintenance and Im assuming you re-did your roof before you installed. Anyone putting solar up make sure you do it at the same time as a roof…

-

Is an ETF simple?

I get your point that in modern society, you can invest in an ETF in a few clicks, but in a way, owning your own infrastructure is simpler. Transform the sun into energy reserves with parts you can buy, understand, and install yourself from wholesalers.

A power company is opaque, carries overhead, and requires complexity to serve at an institutional level. ETFs have a similar complexity/abstraction to their customers.

Re: What a year of solar and batteries saved us in 2025

#109

Post by systemtest »

toomuchtodo wrote: post #47
boringg wrote: post #34

9-11 year payback isn't bad based on the projections. You could probably goose it a bit with inflation of electrical prices (depends on how the electrical policies change and what they pass through). I'll also add theres some O&M coming down the line. Inverters @ year 10, small maintenance and Im assuming you re-did your roof before you installed. Anyone putting solar up make sure you do it at the same time as a roof…

It is essentially a bond return, with the caveat being that solar PV panels will last 25+ years with some degradation and reduction in output. To your point, the best arrangement (imho) is a standing seam metal roof (40-70 year lifetime) with the panels mounted via friction racking with no roof deck penetrations. This avoids the economic cost of pulling everything off the roof to re-roof, and should outlive any homeo…

-

Re: What a year of solar and batteries saved us in 2025

#110

Post by kccqzy »

louwrentius wrote: post #4
kccqzy wrote: post #2

Good analysis. And kudos to the author for saving money. But still 21.6MWh per year excluding solar production seems too high for a household. I use electric heating and drive an electric vehicle, and my household annual energy consumption is about one fifth of that.

From the article: "My wife and I both drive electric cars" That probably explains it.

Yeah but they both work from home. The biggest reason for putting mileage on the car, commuting, is now out.
Post reply on HN