A good way to look at sizing Powerwalls

[mspohr]

A new critical load tiering approach solves the elusive value-of-resilience challenge and facilitates the proliferation of solar-driven microgrids.

Think we can’t place a value on resilience? Think again

 

[Southpasfan]

I probably simply don't have the technical ability to understand the article, but it doesn't seem to put a "value" on resilience, it "assumes" a value of resilience, which is not the same thing.

I am not aware of any part of the grid where, say, if you are a hospital, you can pay a utility more per kwh for guaranteed power. Utilities are already in the business of guaranteed power, they just can't do it 100% of the time.

I think the better measure is sort of alluded to which is comparing solar with BESS to fueled generators.

Maybe what I am missing is in rolling blackouts hospitals never get their power cut off, which I would assume, but I don't think that's because hospitals are charged more. If there was such a system, we could all figure it out.

Like a hospital, everyone's measure of damages in a power outage is different. That's the issue. Hence the different attitudes of posters who live in places where power outages due to storms are regular occurances, those who have health problems where even a few hours is critical, and the rest of us.

 

[mspohr]

I probably simply don't have the technical ability to understand the article, but it doesn't seem to put a "value" on resilience, it "assumes" a value of resilience, which is not the same thing.

I am not aware of any part of the grid where, say, if you are a hospital, you can pay a utility more per kwh for guaranteed power. Utilities are already in the business of guaranteed power, they just can't do it 100% of the time.

I think the better measure is sort of alluded to which is comparing solar with BESS to fueled generators.

Maybe what I am missing is in rolling blackouts hospitals never get their power cut off, which I would assume, but I don't think that's because hospitals are charged more. If there was such a system, we could all figure it out.

Like a hospital, everyone's measure of damages in a power outage is different. That's the issue. Hence the different attitudes of posters who live in places where power outages due to storms are regular occurances, those who have health problems where even a few hours is critical, and the rest of us.

Power resilience has different values for each use. You are right that current billing doesn't make any distinction. The paper proposes a method to value and charge based on that value.

 

[zƬesla]

I am not aware of any part of the grid where, say, if you are a hospital, you can pay a utility more per kwh for guaranteed power. Utilities are already in the business of guaranteed power, they just can't do it 100% of the time.

I used to have websites with a hosting company that advertised being on the same grid as a local hospital in a hurricane-prone part of the country. The benefit was they were a priority for having power restored.

 

[BGbreeder]

I can't speak for all utilities, but the ones that I am familiar with wire things like hospitals into blocks that are priority customers, and not subject to things like rolling blackouts. For the lucky residential customers in the same block, there is no upcharge. Large customers like hospitals have lots of other bargaining chips with utilities, including putting their loads on standby generators during peak power events, or storm damage, off hours demand, etc. I have lived in areas where cell towers were on the priority blocks, and areas where they weren't. I don't get the logic, but it maybe wiring cost.

On one of my commercial accounts we are billed by the single maximum load during the month. Not happy about it, but I haven't invested the capital to fix it- yet.

All the best,

BG

 

[mspohr]

I was thinking that Powerwall users could think of their loads in the same way. Essential high priority loads such as refrigerator, lights are only a small fraction of total use. It would be much cheaper to have a system which met only these essential loads than to try to run everything from the Powerwalls.

 

[holeydonut]

On one of my commercial accounts we are billed by the single maximum load during the month. Not happy about it, but I haven't invested the capital to fix it- yet.

All the best,

BG

And I'm sitting here wondering why the company I work for is getting billed for "Above Standard Energy Consumption" since March even though our office is closed and empty due to COVID-19. Oh yeah, we share a building with some PG&E back office folks and they're probably just doing their typical lame BS to screw the other building tenants.

Also, our commercial per kWh rate during COVID is $0.321.

 

[jjrandorin]

I was thinking that Powerwall users could think of their loads in the same way. Essential high priority loads such as refrigerator, lights are only a small fraction of total use. It would be much cheaper to have a system which met only these essential loads than to try to run everything from the Powerwalls.

Sure, it would be a little cheaper to "run critical loads only" but this is a personal choice. I personally dont see any point in investing enough money to have backup at all, and then not investing enough to backup enough to "live like I want to live".

I personally was not interested in just backing up my fridge. If I wanted to do that, I could have gotten something much cheaper... but I didnt want to, and some powerwall purchasers do, and some dont... and I dont think a complicated formula is going to change what someone wants to run when there is no grid power. Thats personal.

 

[BrettS]

Sure, it would be a little cheaper to "run critical loads only" but this is a personal choice. I personally dont see any point in investing enough money to have backup at all, and then not investing enough to backup enough to "live like I want to live".

I personally was not interested in just backing up my fridge. If I wanted to do that, I could have gotten something much cheaper... but I didnt want to, and some powerwall purchasers do, and some dont... and I dont think a complicated formula is going to change what someone wants to run when there is no grid power. Thats personal.

Yeah, I tend to agree with you. I read the article this morning and I keep going back to this thread to try to post an opinion, but then I give up because I can’t quite decide on what my opinion is.

I have a big saltwater reef tank and I think that would probably be my tier 1 super critical load. If that loses power for too long I could lose thousands of dollars in livestock. Some of which I have had for years. Of course, the fridge is also up there in the critical load department. And I was able to experience running Tier 1 loads only after hurricane Matthew 4 or 5 years ago. I got a small 1800W inverter generator before the hurricane which was able to run the fish tank and the fridge and not much else. After the hurricane hit I had no property damage, but I did lose power for 3 days. And I can tell you that three days of critical loads only is pretty miserable. Especially in Florida when it’s 90+ degrees and super humid.

After that I decided that things like central AC and hot water might not quite be tier 1 critical, but they are definitely close. When hurricane Irma hit I knew I didn’t want to go through what I did with Matthew, so I wound up buying a much larger 7500W portable generator. This was a big step up from the small generator. It was able to run my central AC, as well as my water heater and even my stove (although not at the same time. I’d have to turn off the AC if I wanted to run the water heater or cook something. It also had the disadvantage of needing to be wheeled out of the garage and manually connected to the house and started in the event of a power failure. Luckily Irma didn’t take out my power at all, but I did use that generator for a few multi hour power failures, including one that was about 8 hours during the day. Being able to keep my AC running definitely made things a lot more convenient. I think this is more of a Tier 2 solution as described in the article.

However, I knew that I wanted more than just that generator and that’s where the powerwalls came in. I wanted something that could take over and power the house without any manual intervention. This was especially important for the fish tank in case the power failed when I was not home. I also wanted a solution that ideally would allow me to run the house the way I normally do whether the grid was up or not. Solar and powerwalls seemed like a good solution here, especially if they could help me save money on my power bill every day. It wasn’t a huge deciding factor, but I do also love the environmental factor as well.

I have yet to get through a real power failure with my powerwalls, but I have definitely determined that I am able to run my system off grid for extended times with little to no change in how I use power.

So all that said, things are going to be different for different people. And the type of outage you are planning for matters too. In my case it’s not uncommon to lose power for days after a hurricane, so I want a solution that will be able to keep me comfortable for days until the power comes back on. If you’re just planning for an outage measured in hours then it would be much easier to get by with just tier 1 loads.

 

[Southpasfan]

Yeah, I tend to agree with you. I read the article this morning and I keep going back to this thread to try to post an opinion, but then I give up because I can’t quite decide on what my opinion is.

I have a big saltwater reef tank and I think that would probably be my tier 1 super critical load. If that loses power for too long I could lose thousands of dollars in livestock. Some of which I have had for years. Of course, the fridge is also up there in the critical load department. And I was able to experience running Tier 1 loads only after hurricane Matthew 4 or 5 years ago. I got a small 1800W inverter generator before the hurricane which was able to run the fish tank and the fridge and not much else. After the hurricane hit I had no property damage, but I did lose power for 3 days. And I can tell you that three days of critical loads only is pretty miserable. Especially in Florida when it’s 90+ degrees and super humid.

After that I decided that things like central AC and hot water might not quite be tier 1 critical, but they are definitely close. When hurricane Irma hit I knew I didn’t want to go through what I did with Matthew, so I wound up buying a much larger 7500W portable generator. This was a big step up from the small generator. It was able to run my central AC, as well as my water heater and even my stove (although not at the same time. I’d have to turn off the AC if I wanted to run the water heater or cook something. It also had the disadvantage of needing to be wheeled out of the garage and manually connected to the house and started in the event of a power failure. Luckily Irma didn’t take out my power at all, but I did use that generator for a few multi hour power failures, including one that was about 8 hours during the day. Being able to keep my AC running definitely made things a lot more convenient. I think this is more of a Tier 2 solution as described in the article.

However, I knew that I wanted more than just that generator and that’s where the powerwalls came in. I wanted something that could take over and power the house without any manual intervention. This was especially important for the fish tank in case the power failed when I was not home. I also wanted a solution that ideally would allow me to run the house the way I normally do whether the grid was up or not. Solar and powerwalls seemed like a good solution here, especially if they could help me save money on my power bill every day. It wasn’t a huge deciding factor, but I do also love the environmental factor as well.

I have yet to get through a real power failure with my powerwalls, but I have definitely determined that I am able to run my system off grid for extended times with little to no change in how I use power.

So all that said, things are going to be different for different people. And the type of outage you are planning for matters too. In my case it’s not uncommon to lose power for days after a hurricane, so I want a solution that will be able to keep me comfortable for days until the power comes back on. If you’re just planning for an outage measured in hours then it would be much easier to get by with just tier 1 loads.

Indeed. I was expecting something from the article along the lines of: for the average person the cost of a hotel would be $200 per night, plus $100 of travel cost to get out of the disaster hit area, plus an average of $200 of food spoilage so for a two day outage it’s $700. Not “let’s assume the cost of guaranteed electricity is 50% more (or 100% more) than normal rates.”

Then you would multiply that figure by the expected days of outage over ten years or whatever to get a “cost” - and then compare that cost to the price of powerwalls.