And a “server rack” battery https://signaturesolar.com/shop-all/batteries/eg4-lifepower4/ , which has made battery backup actually affordable at ~$300/kwh. This is 1/3 to 1/5 the price it was previously, and these are LFP batteries, not lead acid, so they will last 15-25 years.
Electrically, wiring one of these in is not difficult and some of them are UL listed and legal in most areas.
The way it works functionally is simple: your ‘all in one offgrind inverter’ powers a subpanel, where most/all your houses circuits are on. It receives power from your main panel, and also solar panels, and it is wired to a battery.
During most of the day, everything in your house is directly powered by solar. Whenever electrical load exceeds solar output and at night, the power comes from the batteries. A prolonged period of low solar output, you configure the all in one to enable battery charging at ~10% remaining state of charge. You can also configure it to only charge during the cheapest time of each day.
You never feed power back to the grid under any circumstance.
You also can wire in a backup generator and relays will cause it to auto-start as needed.
Somewhere like San Diego a system like this will pay for itself extremely rapidly (<4 years) because of the exotically high electric rates.
obviously the Tesla powerwall has offered this for years, it is just expensive
You may already know this, but making it explicit: grid-tie solar with battery backup is a market that predates the powerwall. Tesla just has the best marketing ;) The main problem, as you said, is that this is expensive.
You never feed power back to the grid under any circumstance.
That’s a big downside to this system. The main subsidy for solar has been through generation credits (we’re on SREC II; new installs here are SMART) and very favorable net metering rules.
Well in that case, go install an interlock kit and a generator inlet so your generator can be used conveniently. For emergency situations a generator is just fine. The fuel cost won’t be significant, generators are cheap, even a model big enough to run an entire house with efficient air conditioning. (9 kilowatt or so dual fuel propane generator)
Get a duel fuel generator so you can store fuel for a decade as propane rather than for 30-90 days in the form of gasoline. (diesel is too expensive as a generator to bother with)
Your EPS was never a good source of backup power. Long term everyone is going to have a setup more like I described above with a battery, you’re receiving a large government subsidy in your favor through your net metering deal.
I do now also have a dual fuel generator, as I say at the end of the post. And I’m storing propane.
Sorry I missed that part. Great
You can store gas for a year or longer if you use fuel stabilizer. I do this as well, primarily as backup for the car.
Technically you can. Issues:
fuel stabilizer makes that claim on the bottle but it’s a risky thing to find out it didn’t work the one time you actually need an emergency generator.
10 years (only reason for this limit is this is the rated service life of a propane tank) > 1-2 years
Generators use a mechanical low cost fuel mixing system called a carburetor. After the engine is run, say to test the generator, gasoline is still in the carb. It evaporates over time and has a very high chance of causing later failure. If you are going to use gasoline, run the generator dry when you run it.. (run it until it stops from fuel exhaustion).
1: Looking, I don’t see people having problems with stabilized fuel after ~1y—is this a problem you’ve seen?
2: I agree it’s nicer to be able to just hold onto the propane tank for a decade, but needing to replace the gasoline annually isn’t that bad. I’m planning to put it in my car and being the cans to the gas station to refill. I have a reminder set and I expect it’ll take me about an hour each time? I do think there’s a good reason to store gasoline as well as propane, in case what you end up needing is fuel for the car.
3: In a bit of reading this may not be enough for something that is used as infrequently as I’m expecting to use the generator, because you do still have a bit of gas that doesn’t get burnt even when you run it dry. This is what I was referring to with “doesn’t require gasoline’s level of cleanup from intermittent use”. My current plan is to only run it on gas if I’ve already used all the propane.
1: Looking, I don’t see people having problems with stabilized fuel after ~1y—is this a problem you’ve seen?
Yes. Shockingly high failures. Out of, I dunno, 8 lawnmowers and 4 gas weed-eaters and 3 gas edgars in my life, basically 100% of them have either failed or were extremely difficult to start at one point or another from clogged carburetors and stale gas.
Yes, fuel stabilizer works, but it isn’t perfect and you don’t want to be trying to diagnose the issue when you actually need a generator. It may be at night, or after the heat has failed during an ice storm, or during a rain storm, or when you’re in a hurry to get your workstation back online because you’re missing a critical meeting or demo.
Note that a lot of people using fuel stabilizer are using it for cars. They have much larger orifices, are harder to flood, have computer controlled starting systems etc. The gas can be pretty mediocre and they still run—various videos on youtube people have tried substituting ethanol, etc, and the engine still starts and runs.
It sounds like maybe you’re talking about small engines with stabilized fuel that are used very occasionally and aren’t cleaned out between uses? I’m not talking about storing stabilized fuel inside the generator, but about keeping a gas can with stabilizer in it.
A generator is in that class of “small engines with stabilized fuel that are used very occasionally and aren’t cleaned out between uses”.
In order to clean it out you must disassemble the engine partially, simply running it to fuel starvation is insufficient. Few have the time or tools to do this.
There is fuel still in the engine even after it sputters and dies (fuel starvation)
From experience, stabilized gas from a gas can still doesn’t start the engine as easily as actually new gas from a gas can.
… There is fuel still in the engine even after it sputters and dies
Yes. If you look at our earlier conversation above you can see I’m also storing propane. I’m only planning on using the stored stabilized gas if the propane runs out (or if I need it for the car). Needing to clean the engine thoroughly before putting it away if I do use gas will be a project, but I think a reasonably interesting one.
stabilized gas from a gas can still doesn’t start the engine as easily as actually new gas from a gas can
That’s much more relevant for my plans, though it’s hard to get a sense of how big a consideration this is.
Jefft: obviously the Tesla powerwall has offered this for years, it is just expensive.
What you probably haven’t heard of is there are now Chinese off brand “powerwalls” that work quite well.
It’s a combination of 2 things:
An “all in one” offgrid inverter https://signaturesolar.com/shop-all/off-grid/inverters/ (notice how the prices are not any more than you paid for your sunny boy. off brand though)
And a “server rack” battery https://signaturesolar.com/shop-all/batteries/eg4-lifepower4/ , which has made battery backup actually affordable at ~$300/kwh. This is 1/3 to 1/5 the price it was previously, and these are LFP batteries, not lead acid, so they will last 15-25 years.
Electrically, wiring one of these in is not difficult and some of them are UL listed and legal in most areas.
The way it works functionally is simple: your ‘all in one offgrind inverter’ powers a subpanel, where most/all your houses circuits are on. It receives power from your main panel, and also solar panels, and it is wired to a battery.
During most of the day, everything in your house is directly powered by solar. Whenever electrical load exceeds solar output and at night, the power comes from the batteries. A prolonged period of low solar output, you configure the all in one to enable battery charging at ~10% remaining state of charge. You can also configure it to only charge during the cheapest time of each day.
You never feed power back to the grid under any circumstance.
You also can wire in a backup generator and relays will cause it to auto-start as needed.
Somewhere like San Diego a system like this will pay for itself extremely rapidly (<4 years) because of the exotically high electric rates.
You may already know this, but making it explicit: grid-tie solar with battery backup is a market that predates the powerwall. Tesla just has the best marketing ;) The main problem, as you said, is that this is expensive.
That’s a big downside to this system. The main subsidy for solar has been through generation credits (we’re on SREC II; new installs here are SMART) and very favorable net metering rules.
Well in that case, go install an interlock kit and a generator inlet so your generator can be used conveniently. For emergency situations a generator is just fine. The fuel cost won’t be significant, generators are cheap, even a model big enough to run an entire house with efficient air conditioning. (9 kilowatt or so dual fuel propane generator)
Get a duel fuel generator so you can store fuel for a decade as propane rather than for 30-90 days in the form of gasoline. (diesel is too expensive as a generator to bother with)
Your EPS was never a good source of backup power. Long term everyone is going to have a setup more like I described above with a battery, you’re receiving a large government subsidy in your favor through your net metering deal.
Why? In a very long outage it seems to me like it does much better than generators which need fuel.
I do now also have a dual fuel generator, as I say at the end of the post. And I’m storing propane.
You can store gas for a year or longer if you use fuel stabilizer. I do this as well, primarily as backup for the car.
I do now also have a dual fuel generator, as I say at the end of the post. And I’m storing propane.
Sorry I missed that part. Great
You can store gas for a year or longer if you use fuel stabilizer. I do this as well, primarily as backup for the car.
Technically you can. Issues:
fuel stabilizer makes that claim on the bottle but it’s a risky thing to find out it didn’t work the one time you actually need an emergency generator.
10 years (only reason for this limit is this is the rated service life of a propane tank) > 1-2 years
Generators use a mechanical low cost fuel mixing system called a carburetor. After the engine is run, say to test the generator, gasoline is still in the carb. It evaporates over time and has a very high chance of causing later failure. If you are going to use gasoline, run the generator dry when you run it.. (run it until it stops from fuel exhaustion).
1: Looking, I don’t see people having problems with stabilized fuel after ~1y—is this a problem you’ve seen?
2: I agree it’s nicer to be able to just hold onto the propane tank for a decade, but needing to replace the gasoline annually isn’t that bad. I’m planning to put it in my car and being the cans to the gas station to refill. I have a reminder set and I expect it’ll take me about an hour each time? I do think there’s a good reason to store gasoline as well as propane, in case what you end up needing is fuel for the car.
3: In a bit of reading this may not be enough for something that is used as infrequently as I’m expecting to use the generator, because you do still have a bit of gas that doesn’t get burnt even when you run it dry. This is what I was referring to with “doesn’t require gasoline’s level of cleanup from intermittent use”. My current plan is to only run it on gas if I’ve already used all the propane.
1: Looking, I don’t see people having problems with stabilized fuel after ~1y—is this a problem you’ve seen?
Yes. Shockingly high failures. Out of, I dunno, 8 lawnmowers and 4 gas weed-eaters and 3 gas edgars in my life, basically 100% of them have either failed or were extremely difficult to start at one point or another from clogged carburetors and stale gas.
Yes, fuel stabilizer works, but it isn’t perfect and you don’t want to be trying to diagnose the issue when you actually need a generator. It may be at night, or after the heat has failed during an ice storm, or during a rain storm, or when you’re in a hurry to get your workstation back online because you’re missing a critical meeting or demo.
Note that a lot of people using fuel stabilizer are using it for cars. They have much larger orifices, are harder to flood, have computer controlled starting systems etc. The gas can be pretty mediocre and they still run—various videos on youtube people have tried substituting ethanol, etc, and the engine still starts and runs.
It sounds like maybe you’re talking about small engines with stabilized fuel that are used very occasionally and aren’t cleaned out between uses? I’m not talking about storing stabilized fuel inside the generator, but about keeping a gas can with stabilizer in it.
A generator is in that class of “small engines with stabilized fuel that are used very occasionally and aren’t cleaned out between uses”.
In order to clean it out you must disassemble the engine partially, simply running it to fuel starvation is insufficient. Few have the time or tools to do this.
There is fuel still in the engine even after it sputters and dies (fuel starvation)
From experience, stabilized gas from a gas can still doesn’t start the engine as easily as actually new gas from a gas can.
Yes. If you look at our earlier conversation above you can see I’m also storing propane. I’m only planning on using the stored stabilized gas if the propane runs out (or if I need it for the car). Needing to clean the engine thoroughly before putting it away if I do use gas will be a project, but I think a reasonably interesting one.
That’s much more relevant for my plans, though it’s hard to get a sense of how big a consideration this is.