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Why not both? Even small generators provide a lot of power at once, for a small initial price, but are expensive to run continuously. A battery has low operat

Why not both? Even small generators provide a lot of power at once, for a small initial price, but are expensive to run continuously. A battery has low operating cost, but one large enough to run a house off of solar power, year round, is extremely expensive. A battery that is large enough to work 99% of the time is much cheaper, and a generator can fill in that 1%, operating only a few hours a year, at a very low cost.

jareds 2y ago
In my case the answer to why not both was unattended reliability and piece of mind. If it's raining and we lose power we have about four hours before we start to get flooding do to a sump pump not running. Our backup generator will run a self test every week and automatically power the house with a ten second delay when the power goes out. While I suspect solar and a battery backup would keep the sump pump running for a long time it's nice to not need to choose what to run and monitor our power usage during an outage. It's also nice to not worry about power while were on vacation. With solar and a battery backup I'd be concerned about checking it while away from the house. I realize I"m somewhat of a unique situation though in just how quickly we get flooding when power goes out.
- TheSpiceIsLife 2y ago
  You've already got a solution, and often the cheapest solution is the one you already have. There's no technical reason a generator + battery (and solar?) setup couldn't be configured to run off battery till the battery reaches a preconfigured state of charge then call for the generator.
  - jareds 2y ago
    DO you have commercially available examples of this setup? While I agree there's no technical reason this wouldn't work when doing research for our generator all the hole house generators use a transfer switch so it's either running the entire house completely disconnected from the grid or turned off and running the house from the grid. Solar didn't make sense for us given the costs and our time horizon, but it's always been something I've been interested in. A solar system with a natural gas generator backup to charge the batteries would be nice, especially for shorter outages so we wouldn't need to hear the generator running.
    - TheSpiceIsLife 2y ago
      Look for UPS with generator input. A business that sells solar with battery backup would know the current product range. I’m only really familiar with industrial kit tupicalled used in data centres.
      - TheSpiceIsLife 2y ago
        typically*
ethagnawl 2y ago
This is what I do and it's worked quite well so far -- we haven't had an extended outage to contend with yet. I have a relatively small battery as these things go (Bluetti AC200 Max w/ extended battery) but it's enough for our essentials. The game changing aspect of it, IMO, is that acts as a buffer for my generator, solar panels and whatever else I may want to use to power it in the future (maybe an EV?).
- rented_mule 2y ago
  I do something like that, but a little bigger, and it works great. I put it together after a two-week outage a few years ago (we get multi-day outages almost every year). I have two Bluetti AC300s and four B300 batteries. That gives me ~12 KWh (~24 hours for us) and 240 V so that it can feed the entire house. The buffer thing you mentioned is key... our average usage is around 400 W, so the generator can be pretty small and the battery system will handle the peaks. We have a hand carryable 2 KW inverter generator. The challenge with this system is that you need 240 V to charge the two Bluetti units (or two 120 V lines on opposite legs of a 240 V feed to ensure the proper phase relationship). I got around this by buying three Mean Well 48 VDC power supplies (meant for large LED installations). Each will do ~500 W. I plug them into the Bluetti units as if they were solar panels. Running the generator through them for 6-8 hours a day is enough to keep the batteries going indefinitely. That's 2-3 gallons of gas per day. And the first day of an outage requires no gas. In the summer, we have a handful of solar panels I put up in the yard to keep the batteries topped up when not being used for outages (our outages are mostly wind+snow events in winter). Our evaporative cooler, chest freezer, and washer / dryer run off the batteries while the panels are up.
bluGill 2y ago
So far I have never seen a system that works as it would need to for that to work. They all have weird fine print which means that despite having both only one is used when backup in needed.
sapientiae3 2y ago
This is the way.
SmellTheGlove 2y ago
I live in Seattle and I was originally going to go with batteries. However, the half of the year when our power is most likely to go out is also the half of the year where there is very little sun. So for a prolonged outage I’d either need a lot of battery or a generator. For short outages, a battery made sense, but the cost was a lot higher. I ended up with a 6.5kW portable tri-fuel generator instead. It cost me $1300 and I spent a little more for a plumber to add a gas stub to connect it to. I did my own electrical work which saved some money, but wouldn’t have been much more for an electrician. It can run my whole house indefinitely (obviously with some maintenance - it’s a small engine), except for the A/C which generally isn’t needed most of the year, and with some manual load shedding we can run the hot water too. I live in the city and shouldn’t need any of this, but Seattle is poorly run so we have lots of outages from trees hitting things. Often a different transformer on the same block because the city will repair them but not take the time to trim the trees near the lines on the same block. I’ve had to throw some food away the last two outages (both in the last 6 months) so this won’t take long to pay for itself!

jareds 2y ago

In my case the answer to why not both was unattended reliability and piece of mind. If it's raining and we lose power we have about four hours before we start to get flooding do to a sump pump not running. Our backup generator will run a self test every week and automatically power the house with a ten second delay when the power goes out. While I suspect solar and a battery backup would keep the sump pump running for a long time it's nice to not need to choose what to run and monitor our power usage during an outage. It's also nice to not worry about power while were on vacation. With solar and a battery backup I'd be concerned about checking it while away from the house. I realize I"m somewhat of a unique situation though in just how quickly we get flooding when power goes out.

TheSpiceIsLife 2y ago
You've already got a solution, and often the cheapest solution is the one you already have. There's no technical reason a generator + battery (and solar?) setup couldn't be configured to run off battery till the battery reaches a preconfigured state of charge then call for the generator.
- jareds 2y ago
  DO you have commercially available examples of this setup? While I agree there's no technical reason this wouldn't work when doing research for our generator all the hole house generators use a transfer switch so it's either running the entire house completely disconnected from the grid or turned off and running the house from the grid. Solar didn't make sense for us given the costs and our time horizon, but it's always been something I've been interested in. A solar system with a natural gas generator backup to charge the batteries would be nice, especially for shorter outages so we wouldn't need to hear the generator running.
  - TheSpiceIsLife 2y ago
    Look for UPS with generator input. A business that sells solar with battery backup would know the current product range. I’m only really familiar with industrial kit tupicalled used in data centres.
    - TheSpiceIsLife 2y ago
      typically*

ethagnawl 2y ago

This is what I do and it's worked quite well so far -- we haven't had an extended outage to contend with yet. I have a relatively small battery as these things go (Bluetti AC200 Max w/ extended battery) but it's enough for our essentials. The game changing aspect of it, IMO, is that acts as a buffer for my generator, solar panels and whatever else I may want to use to power it in the future (maybe an EV?).

rented_mule 2y ago
I do something like that, but a little bigger, and it works great. I put it together after a two-week outage a few years ago (we get multi-day outages almost every year). I have two Bluetti AC300s and four B300 batteries. That gives me ~12 KWh (~24 hours for us) and 240 V so that it can feed the entire house. The buffer thing you mentioned is key... our average usage is around 400 W, so the generator can be pretty small and the battery system will handle the peaks. We have a hand carryable 2 KW inverter generator. The challenge with this system is that you need 240 V to charge the two Bluetti units (or two 120 V lines on opposite legs of a 240 V feed to ensure the proper phase relationship). I got around this by buying three Mean Well 48 VDC power supplies (meant for large LED installations). Each will do ~500 W. I plug them into the Bluetti units as if they were solar panels. Running the generator through them for 6-8 hours a day is enough to keep the batteries going indefinitely. That's 2-3 gallons of gas per day. And the first day of an outage requires no gas. In the summer, we have a handful of solar panels I put up in the yard to keep the batteries topped up when not being used for outages (our outages are mostly wind+snow events in winter). Our evaporative cooler, chest freezer, and washer / dryer run off the batteries while the panels are up.

bluGill 2y ago

So far I have never seen a system that works as it would need to for that to work. They all have weird fine print which means that despite having both only one is used when backup in needed.

sapientiae3 2y ago

This is the way.

SmellTheGlove 2y ago

I live in Seattle and I was originally going to go with batteries. However, the half of the year when our power is most likely to go out is also the half of the year where there is very little sun. So for a prolonged outage I’d either need a lot of battery or a generator. For short outages, a battery made sense, but the cost was a lot higher. I ended up with a 6.5kW portable tri-fuel generator instead. It cost me $1300 and I spent a little more for a plumber to add a gas stub to connect it to. I did my own electrical work which saved some money, but wouldn’t have been much more for an electrician. It can run my whole house indefinitely (obviously with some maintenance - it’s a small engine), except for the A/C which generally isn’t needed most of the year, and with some manual load shedding we can run the hot water too. I live in the city and shouldn’t need any of this, but Seattle is poorly run so we have lots of outages from trees hitting things. Often a different transformer on the same block because the city will repair them but not take the time to trim the trees near the lines on the same block. I’ve had to throw some food away the last two outages (both in the last 6 months) so this won’t take long to pay for itself!