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It’s interesting seeing the difference in how solar is usually talked about versus backup generators. Whole-home generators are expensive and get used rarely b

It’s interesting seeing the difference in how solar is usually talked about versus backup generators. Whole-home generators are expensive and get used rarely but are often justified as a “just in case”. Solar doesn’t enjoy this kind of leniency, unfortunately. Being less dependent on the grid has many benefits that get ignored over a perceived return on value.

briHass 2y ago
At least around here, backup generators are for outages that happen when solar would be mostly useless: heavy storms or during Winter. Cheap and safe batteries paired with solar will help, but the capacity will likely still be an issue for extended outages.
- epistasis 2y ago
  An islanding solar system with storage is not useless during storms or the winter, it still generates during the day. Not sure where your "around here" is, though.
  - nine_k 2y ago
    Do solar panels ever get trapped under large amounts of snow the day after a strong snow storm?
    - timschmidt 2y ago
      Sure, but with a couple inches of snow on them, mine still generate power. And in areas which regularly receive snow, roof pitches are generally steep enough to encourage it to slide off else the building would suffer overloading. Worst case a push broom or squeegee with a very long handle works wonders. Also fairly trivial to rig up a resistive heating system for melting the snow in cases where the above isn't possible. Even possible to automate it based on time of day and expected power input.
      - magicalhippo 2y ago
        > Also fairly trivial to rig up a resistive heating system for melting the snow Couldn't you just run power through the solar cells as if they were giant LEDs? Or don't they like that?
        timschmidt 2y ago
        It is possible to back-feed power through a solar cell such that it emits photons (or maybe just heat - I'm not entirely clear on that). But all solar panels include diodes to prevent this and provide protection from hooking them up in reverse.
        magicalhippo 2y ago
        Ah, makes sense. As you mentioned though, easy enough to fit some thermal heating foil on the backside unless you're using bifacials.
    - mechagodzilla 2y ago
      It does happen occasionally, but it's rare that my panels are covered for more than a day or so. Heavy snows almost always slide off within 36 hours - sometimes a light snow (~3" or so) can cover it for a while because it's not heavy enough to slide off from gravity. The panels are very low friction compared to a normal roof.
    - jbuzbee 2y ago
      Yeah - When covered in even a moderate amount of snow, output drops almost all the way off. I had thought that being black, they would melt off quickly, but that doesn't appear to be the case. As an aside, my daughter's neighbor has solar and after a big snowstorm, a foot of snow slid off his panels, right into the side of her house destroying a basement window and blowing shattered glass 5 foot into the basement.
jaggederest 2y ago
Sadly at least where I live the backup generators are well-used, winter and summer alike. There was a period of about a year where we went no more than a week or two between power outages. Absolutely a lifesaver, when you have a freezer full of frozen goods. In this context I'm saving my pennies for a solar and battery set up - it both makes financial sense when connected to the grid, and obviates the annoying side effect and high cost of running the backup generator during outages, unless they're extremely lengthy.
- nine_k 2y ago
  How costly is it to run a backup generator? A gallon of gasoline produces about 36 kWh, and costs about $3.6. Assuming that the motor + generator + inverter chain has efficiency is 25%, it's 9 kWh of electricity per gallon, or about 40 ¢ per kWh. Likely twice as expensive as the grid, but fine for a few days.
  - jaggederest 2y ago
    Well, mine is propane, and propane is substantially less energetic than gasoline, and is also subject to delivery fees. The issue you really run into is that, even at idle, the generator burns a fixed amount of propane. The minimum is about 2 gallons per hour. Which is roughly $6 So you can imagine that, for 3 days of usage, $500 provides a strong incentive to seek out alternative sources of power. We run about $1200 a year in propane costs for the generator, estimated.
    - tzs 2y ago
      > The issue you really run into is that, even at idle, the generator burns a fixed amount of propane. The minimum is about 2 gallons per hour. Which is roughly $6 All the loads that I might consider a generator for are intermittent (well pump, fridge, microwave, space heater). I've wondered if it would make sense to get inverters for the fridge, microwave, and heater and get a pool of batteries, and just use the generator for charging batteries and powering the well pump. With a sufficient number of batteries in the battery pool it should be possible to only need to run the generator when there are sufficient batteries to charge that the generator can run at its most efficient output.
overstay8930 2y ago
Whole home generators are miles cheaper than a solar-battery setup. I can get 10kw of backup power tied into my house for 5k with an automatic switch, but that barely covers the labor costs for a solar system, and you still have to buy the rest of it. Sure you can DIY it and get close, but most people are not going to do that.
- jaredhallen 2y ago
  You can also DIY a generator. Mine is tied into my 500 gallon propane tank, and would probably run the house for a month or more. And it cost less than $2k. No automatic transfer switch, but I actually prefer that because if the power goes out for a short time I don't start it up, and I turn it off at night as well.
toast0 2y ago
Depends on your local grid reliability. It would have been foolish to have a whole house generator where (and when) I lived before I moved where I am. Where I live now, utility power is less than three nines, and some years doesn't quite make it to two. Solar without storage usually is grid tied, but even if it runs isolated, it doesn't help overnight. Batteries for a multiday outage are still quite expensive compared to a generator. A whole house battery would be nice though, at least some of the systems can switch power quick enough that I wouldn't need UPSes at all my computers, and the battery maintenance that requires (of course, the large system would probanly require maintenance)

briHass 2y ago

At least around here, backup generators are for outages that happen when solar would be mostly useless: heavy storms or during Winter. Cheap and safe batteries paired with solar will help, but the capacity will likely still be an issue for extended outages.

epistasis 2y ago
An islanding solar system with storage is not useless during storms or the winter, it still generates during the day. Not sure where your "around here" is, though.
- nine_k 2y ago
  Do solar panels ever get trapped under large amounts of snow the day after a strong snow storm?
  - timschmidt 2y ago
    Sure, but with a couple inches of snow on them, mine still generate power. And in areas which regularly receive snow, roof pitches are generally steep enough to encourage it to slide off else the building would suffer overloading. Worst case a push broom or squeegee with a very long handle works wonders. Also fairly trivial to rig up a resistive heating system for melting the snow in cases where the above isn't possible. Even possible to automate it based on time of day and expected power input.
    - magicalhippo 2y ago
      > Also fairly trivial to rig up a resistive heating system for melting the snow Couldn't you just run power through the solar cells as if they were giant LEDs? Or don't they like that?
      - timschmidt 2y ago
        It is possible to back-feed power through a solar cell such that it emits photons (or maybe just heat - I'm not entirely clear on that). But all solar panels include diodes to prevent this and provide protection from hooking them up in reverse.
        magicalhippo 2y ago
        Ah, makes sense. As you mentioned though, easy enough to fit some thermal heating foil on the backside unless you're using bifacials.
  - mechagodzilla 2y ago
    It does happen occasionally, but it's rare that my panels are covered for more than a day or so. Heavy snows almost always slide off within 36 hours - sometimes a light snow (~3" or so) can cover it for a while because it's not heavy enough to slide off from gravity. The panels are very low friction compared to a normal roof.
  - jbuzbee 2y ago
    Yeah - When covered in even a moderate amount of snow, output drops almost all the way off. I had thought that being black, they would melt off quickly, but that doesn't appear to be the case. As an aside, my daughter's neighbor has solar and after a big snowstorm, a foot of snow slid off his panels, right into the side of her house destroying a basement window and blowing shattered glass 5 foot into the basement.

jaggederest 2y ago

Sadly at least where I live the backup generators are well-used, winter and summer alike. There was a period of about a year where we went no more than a week or two between power outages. Absolutely a lifesaver, when you have a freezer full of frozen goods. In this context I'm saving my pennies for a solar and battery set up - it both makes financial sense when connected to the grid, and obviates the annoying side effect and high cost of running the backup generator during outages, unless they're extremely lengthy.

nine_k 2y ago
How costly is it to run a backup generator? A gallon of gasoline produces about 36 kWh, and costs about $3.6. Assuming that the motor + generator + inverter chain has efficiency is 25%, it's 9 kWh of electricity per gallon, or about 40 ¢ per kWh. Likely twice as expensive as the grid, but fine for a few days.
- jaggederest 2y ago
  Well, mine is propane, and propane is substantially less energetic than gasoline, and is also subject to delivery fees. The issue you really run into is that, even at idle, the generator burns a fixed amount of propane. The minimum is about 2 gallons per hour. Which is roughly $6 So you can imagine that, for 3 days of usage, $500 provides a strong incentive to seek out alternative sources of power. We run about $1200 a year in propane costs for the generator, estimated.
  - tzs 2y ago
    > The issue you really run into is that, even at idle, the generator burns a fixed amount of propane. The minimum is about 2 gallons per hour. Which is roughly $6 All the loads that I might consider a generator for are intermittent (well pump, fridge, microwave, space heater). I've wondered if it would make sense to get inverters for the fridge, microwave, and heater and get a pool of batteries, and just use the generator for charging batteries and powering the well pump. With a sufficient number of batteries in the battery pool it should be possible to only need to run the generator when there are sufficient batteries to charge that the generator can run at its most efficient output.

overstay8930 2y ago

Whole home generators are miles cheaper than a solar-battery setup. I can get 10kw of backup power tied into my house for 5k with an automatic switch, but that barely covers the labor costs for a solar system, and you still have to buy the rest of it. Sure you can DIY it and get close, but most people are not going to do that.

jaredhallen 2y ago
You can also DIY a generator. Mine is tied into my 500 gallon propane tank, and would probably run the house for a month or more. And it cost less than $2k. No automatic transfer switch, but I actually prefer that because if the power goes out for a short time I don't start it up, and I turn it off at night as well.

toast0 2y ago

Depends on your local grid reliability. It would have been foolish to have a whole house generator where (and when) I lived before I moved where I am. Where I live now, utility power is less than three nines, and some years doesn't quite make it to two. Solar without storage usually is grid tied, but even if it runs isolated, it doesn't help overnight. Batteries for a multiday outage are still quite expensive compared to a generator. A whole house battery would be nice though, at least some of the systems can switch power quick enough that I wouldn't need UPSes at all my computers, and the battery maintenance that requires (of course, the large system would probanly require maintenance)