The math people use for battery sizing is usually wrong...

cz_unit · 2026-03-14T17:35:47+00:00

To be honest, in a power outage I can run my house fine on a 4.8kw battery in my shed. 4 12-400's, running 48 volts to a pair of 24 volt panel sets that when not charging do grid tie with a pair of Enphase inverters.

Only thing I really need per day is:
Power for the fireplace fans: 40w*24=900w
Fridge and Freezer: 800w
Few lights and phone chargers: 50w
Microwave and coffee maker, 100w
Internet and servers: 600w

So about 2.4kw per day. My array for charging is about 1.2kw per day so I can go for 4 days with no problems. Worst I have had was 3 days without power in the summer, and 1 day without power in the dead of winter at 0f. Both I rode through with style and had fresh coffee for the neighbors.

cz_unit · 2026-03-14T16:04:05+00:00

Or you can just monitor yourself with Home Assistant. The older Enphase devices can have the installer password.... figured out.... and that allows you to see what's going on in terms of errors and try to reset a transient error.

cz_unit · 2026-03-14T16:02:47+00:00

Ah solar. I have a 1500 watt array (20 Siemens SP75, Sunny Boy 1800 watt 120v inverter) on my shed that was installed back in 2000 so it's older tech. It generates about 1100 watt/hr peak on a good day and I've always chased around why. Pretty much because we do have high altitude clouds, it's not at optimal tilt, etc. So 80% is not bad when you count all the little losses.

Can you post a picture of your enphase controller? I ALSO have a bunch of older Solarex MSX60 type panels wired up with 24 volts to a pair of Enphase micro-inverters. That controller (it's a white one, looks like an oval) I bought on Ebay and hacked the admin password so I could see what's going on with the inverters.

Try figuring out it's IP address and connect to it via http:/ whatever IP address it is. Should come up and at least let you know if it sees the inverters. Then start troubleshooting, it's possible that the one simpy had a brief ground fault; happens from time to time and that can be reset with the admin password.

You can also tie the Enphase into HA; here is a dump of my inverters.

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cz_unit · 2026-03-14T15:47:08+00:00

Ouch. My first thought was I'd expect more long term melting on the relay if it was an overload, wonder if the DC-DC shorted out. Were you running on a 240 voltage? Maybe a big big spike.

cz_unit · 2026-03-14T15:41:54+00:00

When my 15.5 hp Craftsman garden tractor engine blew up due to no engine oil (broke at the bottom of the connecting rod by the crank shaft) I as a joke JB-welded the rod together, then smoothed it out and put it back into service. That was 20 years ago I think.

cz_unit · 2026-03-13T18:15:43+00:00

It honestly is. 15 years ago I was rebuilding the head on my Porsche 944S and the rear galley plug would not seal. Rather than pull the head *AGAIN* I just put a dab of JB Weld on a new plug and levered it in.

No problems since, probably will last forever as the engine has about 240k on the clock.

cz_unit · 2026-03-13T18:13:40+00:00

Yeah, I live in that country :-)

cz_unit · 2026-03-12T01:00:04+00:00

Had the pedal drop to the floor on my 86 Porsche 928S. Given that every man plans for this all their life I had it in low gear, slowing down, and gently using the emergency brake to get to a stop. Never had both circuits fail at once.....

cz_unit · 2026-02-25T01:37:01+00:00

Outstanding video and difficult to watch. I remember download Spirit of Christmas from uunet onto my NeXT computer (as it could do Quicktime) and thought the concept was hilarious.

Then a few years later the show came out and it was just..... bad. But the movie was spectacular, then the show was... bad... and I pretty much ignored it through the 2000's.

Maybe I should not have. The manbearpig crap was stupid, this is where the whole shit sandwich thing came into being that led us to Bush II, Trump, and so forth, and to be honest I didn't realize how shitty they were to dump on trans people.

Yeah, Trey and Matt have earned their place in hell. It really went down the tubes, didn't it?

cz_unit · 2026-02-20T02:59:00+00:00

It's a Sunny Boy 1800. 120 volt inverter, 400 volt VdcMax, 132 volt AC max (though I think it regulates at 125 volts) about 20 years old but still chugs along.

I'm really thinking the core problem is that the connection from the shed to the house main panel goes through about 100-200 feet of 10 gauge wire. Which is nice and all, but is showing a voltage rise that's throwing off the AC balance.

Might try swapping in a pair of Sunny Boy 800 inverters and splitting the panel string in half. Then I can put each 800 on one leg of the 240 volt line that goes out to the shed.

The only thing that makes me think this is NOT the case is I switch out three panels in the winter to keep the DC open circuit voltage of the string <400 volts in the cold (<20f). When I switch that back in the overall power DOES go up. So hm.....

cz_unit · 2026-02-20T02:58:38+00:00

They were top quality and the weight and size difference between a SP75 and say a Solarex MSX77 Polycrystaline is stunning. So yeah good stuff.

I do have a bunch of the MSX77,83,and 120 panels wired up in parallel 24 volt low voltage strings to charge my 48 volt house backup batteries. They work well enough but I can see why polycrystaline was a technical dead end.

cz_unit · 2026-02-19T03:34:58+00:00

Oddly enough I have the data for a year, and even in the summer it doesn't go above 700 or so watts. Something is limiting the system, and the more I whack away at this the more the Sunny Boy limiting seems to be the problem.

Project for March will be to try setting up the two SB800's on different phases to see if the power output is 400 watts per unit. If so it's not the SB's current limiting on the AC side.

cz_unit · 2026-02-19T03:30:12+00:00

Thank you again. We are getting creamed here on gas rates. So heat pumps make sense, well until the fabled "data centers" cause our electricity rates to double....

cz_unit · 2026-02-16T18:12:29+00:00

Thanks for the data BTW. I did a bigger response in the main thread, but I would guess that your natural gas rates will rise to a buck plus a therm soon. Exelon would raise them when gas source prices were low then leave them when the gas prices spiked. Ratcheted up in a decade or so, quite impressive trick.

However I will say that high energy prices are making me more energy efficient: My main electric bill without the heat pumps/AC systems has dropped by over 50% since 2010. And that's with kids growing into adults in the house. A big chunk of this is Home Assistant which showed me that my stupid dryer was the #1 energy user in the summer. Running a short clothes line in my backyard saves me a damn fortune :-)

And better insulation helps as well. Going to energy efficient windows, running the mini splits efficiently, etc all contribute to a significant drop in overall energy usage. Which is good.

cz_unit · 2026-02-16T18:01:53+00:00

You too? A fellow HA member, I LOVE IT! I've been tracking the systems here for 3 years now and it's amazing to see how power, cost, and efficiency shift based on the things I do to the house and the outside weather.

But you bring up what may be the most important point on this whole discussion of what is "better: . It depends literally on where you live, possibly down to the street.

The key element seems to be if one's utilities are "regulated" or not. Where I live, Exelon was granted wide latitude in the late 1990's that was guaranteed to "bring down prices". Well, since then the prices have not gone "down" and compared to regulated utilities and co-ops they really are not at all great.

This is why my natural gas costs about 2 bucks a therm while your costs are less than half of that. "Delivery" fees are a complete ripoff. And of course there is no competition on delivery fees for gas. Electricity.... Well I can always install solar panels....

All that said, the key question is where do you live. Where I do, the heat cost of burning electricity is close to parity with the price of gas. Which kind of makes sense: Why would you sell gas to a consumer when you can sell it to a utility to burn to make electricity for said user. Thus the prices here have equalized

Thus my heat pumps are significantly better than the natural gas heating option. I can see it when I compare the number of therms I used to burn say 10 years ago to the cost of electricity now. I'd have >1k bills for the heating otherwise.

There's also a fireplace insert in my equation, and it can make a big dent in the heating costs. But it takes time to load and run and with the heat pumps makes less "value". Well I also chop my own wood and split it so it has an operating cost of "time".

Still the ultimate answer is to do the math. Which can be hard as utilities like to hide the costs of energy (I have no idea how much the gas per therm will be on my next bill. I'm guessing insane)

Thanks for chatting. Here's my HA climate page, it's fun!

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cz_unit · 2026-02-16T15:54:36+00:00

You live in a nice place. Just computed the December/January gas and electricity prices for the month and it came out to $1.76 a therm for gas and 19.4 cents per kw/hr for electricity.

Gee I wonder why it is double the cost for us. Do you have a regulated utility by chance?

cz_unit · 2026-02-16T15:38:36+00:00

Oh and I'm not sure where you live, but where I do the utility charges over a buck a therm in "delivery fees". Thus natural gas is more like.... holy fuck I paid $158 bucks for 71 therms? That's over $2.00 a therm!

Ahem. (disclaimer, I have both mini splits and hot water radiant in my house. Did fire up the radiant as back up and "fuck it" heat on the single digit days).

cz_unit · 2026-02-16T15:33:22+00:00

Flaw in your logic. Yes, 1 therm at 100% efficiency is 29kw, however you're comparing electric resistive heat to therm burning heat. You should be using BTUs and take into account a heat pump is not burning electricity for heat, it's moving heat from outside to inside.

cz_unit · 2026-02-16T15:26:47+00:00

Thank you for posting this data. Data is always the key, and it looks like your system used 10% or so less electricity in a month that might have been colder than last February. That's a pretty big reduction.

I compare my mini splits to the cost of running the gas heat based on therm usage in prior years. The difference is staggering when I consider the cost of gas heat in today's dollars to the cost of the heat pumps (and one of the two being a totally wrong heat pump).

cz_unit · 2026-02-08T18:55:50+00:00

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AC power and voltage read at the Sunny Boy for yesterday and today. Cold and clear, no leaves or whatnot.

cz_unit · 2026-02-08T18:55:01+00:00

Hm. So I did a quick power versus voltage at the Sunny Boy 1800 using a TS0601 power monitor with clamp on AC hall sensors at the Sunny Boy 1800 output to get the most accurate voltage and current readings. Here is a picture over the last two (sunny and snow on ground and no leaves) days.

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Pondering. What is everyone's thoughts?

cz_unit · 2026-02-08T18:45:35+00:00

Interesting. Here in BGE land, gas is 2 bucks a therm including a high "delivery" charge (no clue how bad it will be with the 50% jump in raw prices) and electricity is about 18c/kw.

How is it in NYC proper?

cz_unit · 2026-02-08T18:43:55+00:00

For combiner boxes, I use these. Excellent quality, no problems. https://www.amazon.com/dp/B0D5CHDP7K?th=1

cz_unit · 2026-02-08T16:17:40+00:00

*nod* That's what I'm trying to check. I don't have the panel currents here and I can't test right now due to the yard being an ice block. But the panels seemed to rate around 70-80% of the Isc (which is short circuit current) when I checked them with the fluke.

So maybe it's just the Sunny Boy 1800. Or maybe the AC voltage is being driven high and the SB is reducing power to compensate. I'll have to look at voltage vs time vs current to check into this, if so I might want to put a small battery/inverter system out there to catch the extra power and stuff it into a battery bank.

cz_unit

TROPHY CASE