Batteries For Home Standby Power

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mkgrady

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Massachusetts
I have a customer that asked for a quote for a standby generator for his townhouse condo. I gave him the quote for a 16kw unit. It was going to power his entire load with load shedding relays on the electric oven, dryer and AC. Now he says he does not think the condo board will approve a standby because of the noise during exercising or running during an outage. He is suggesting a battery and an inverter.

My response without any real experience with batteries powering a home is that it would be expensive. He wants me to look into it and I am willing. If nothing comes of it I should still learn something. He has plenty of room in his unfinished basement for batteries.

He is willing to forget about powering all that a 16kw standby could handle. He listed all the critical things that we can all imagine....gas burner for heat system, refrigerator, tv, WiFi, microwave, a few
Lights, etc.. I explained that some of these loads are connected to circuits that supply other than the critical stuff and the system would have to be large enough to power whatever is connected or plugged in.

I’m looking for some feedback on how practical this concept is. I would assume the system would need about 5kw peak load and have an average output of 2kw. These numbers are just shooting from the hip. If these numbers are anywhere near close, how big of a battery would I need to survive a power outage for four days?

My gut tells me the battery bank would be enormous, the inverter battery charger would cost a fortune and I’m not sure what the transfer equipment would be. Anybody have opinions on this?
 
Inverter/battery boils down to Amp-hours on the batteries, based on battery voltage, inverter efficiency and load. But four days? Expensive is an understatement. The larger systems I'm familiar with in the power industry are UPS systems for critical system backup. The building load is on a generator. They make generators that can be insulated and muffled to the point of near silence, so that would be my suggestion. Transfer switch costs would be the same either way. My whole house generator (propane) can't even be heard until I get within a few feet and it's nothing special....just a Honeywell sold by Home depot. It exercises once a week for 15 minutes. The neighbors would be drooling with envy during an outage.
 
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Those who power their entire home off-grid usually have thousands of watts of panels and scores of high-capacity batteries.

Myself, I have a measly four 105-Ah of batteries and I'm lucky to get a day out of running just my furnace.
 
180612-2201 EDT

I agree with your 2 and 5 kW guesses. Three days at 5 kW is 5*24*3 = 360 kWH, and at 2 kW is 144 kWH.

A typical car battery might be 12*80/1000 = 0.96 kWH. Car batteries are about $100 each. 360*100 = $36,000.

The extremely rare power outage does not justify this kind of capital cost, maintenance, and replacement. And you don't want that many batteries in your basement.

Get a small quiet car engine and alternator on a trailer, or power take off on a car.

In my life time, a fairly long time, I have had less than two weeks of total outage. The longest single outage was about 5 days for the great eastern blackout. I use a Honda 5kW portable for backup, not quiet.

I also believe everyone should have a backup generator. In my neighborhood probably less than 3% have backup, and every neighbor could afford a generator. Few would really need more than 5 kW capability. However, most would not know how to get along with 5 kW.

Our area has relatively low cost natural gas.

.
 
gar said:
180612-2201 EDT

I agree with your 2 and 5 kW guesses. Three days at 5 kW is 5*24*3 = 360 kWH, and at 2 kW is 144 kWH.

A typical car battery might be 12*80/1000 = 0.96 kWH. Car batteries are about $100 each. 360*100 = $36,000.

The extremely rare power outage does not justify this kind of capital cost, maintenance, and replacement. And you don't want that many batteries in your basement.

Get a small quiet car engine and alternator on a trailer, or power take off on a car.

In my life time, a fairly long time, I have had less than two weeks of total outage. The longest single outage was about 5 days for the great eastern blackout. I use a Honda 5kW portable for backup, not quiet.

I also believe everyone should have a backup generator. In my neighborhood probably less than 3% have backup, and every neighbor could afford a generator. Few would really need more than 5 kW capability. However, most would not know how to get along with 5 kW.

Our area has relatively low cost natural gas.

.
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Based on my bill, my consumption, even during the summer, is max about 30 kW-hr/day, so 3 days, with AC would be 120 kW-hr. The Tesla Powerwall 2, less inverter, is $6,000 a pop for 13.5 kW-hr at a rate of up to 5 kW. You would need 9 units for a total of $54,000 in batteries alone
 
For less than the cost of all those batteries you can buy a totally self-contained RV trailer which you could easily live in for a week before having to restock gas for genny, water and propane, and dump waste. Just find a local RV storage lot or a willing homeowner with some unused backyard and park it until needed.

Bonus: It's really useful for those weekend getaways!
 
gadfly56 said:
Based on my bill, my consumption, even during the summer, is max about 30 kW-hr/day, so 3 days, with AC would be 120 kW-hr. The Tesla Powerwall 2, less inverter, is $6,000 a pop for 13.5 kW-hr at a rate of up to 5 kW. You would need 9 units for a total of $54,000 in batteries alone
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Your calculation is not taking account for the energy the PV system would be contributing. The Tesla batteries are designed to work with a PV systems that is generating most of the energy. It will help make up for peak loads that are greater than the PV is producing and energy at night when there is no PV energy. In most cases you would not connect the AC to the critical load panel supplied by the Tesla batteries. If you really want everything backed up and to function like you have utility power then you will need to pay the price for more batteries.

BTW
The Tesla batteries have a builtin inverter. They simply connected to a 2P30 back feed breaker in the critical/backup loads panel.
 
tesla makes a pretty big battery that is lithium ion and is made for this kind of thing. Not cheap but do you really want a bunch of lead acid batteries in someone's townhouse?

another option is to suggest the customer buy one or more of these units.

https://www.amazon.com/Goal-Zero-Po...TF8&qid=1528906889&sr=8-9&keywords=yeti+power

They are not cheap but one can plug just about anything into it. You would need to come up with some kind of xfer switch arrangement for their gas fired furnace so they can plug into the power station. They can be recharged by solar if you have enough solar PV. But if they are judicious in their use of it they can probably last a day or two with a couple of these units.
 
curt swartz said:
Your calculation is not taking account for the energy the PV system would be contributing. The Tesla batteries are designed to work with a PV systems that is generating most of the energy. It will help make up for peak loads that are greater than the PV is producing and energy at night when there is no PV energy. In most cases you would not connect the AC to the critical load panel supplied by the Tesla batteries. If you really want everything backed up and to function like you have utility power then you will need to pay the price for more batteries.

BTW
The Tesla batteries have a builtin inverter. They simply connected to a 2P30 back feed breaker in the critical/backup loads panel.
Click to expand...

The OP's customer lives in a condo. "No solar panels for you."

Even with a built in inverter you'll need some infrastructure to set up 9 batteries to feed the condo.
 
petersonra said:
tesla makes a pretty big battery that is lithium ion and is made for this kind of thing. Not cheap but do you really want a bunch of lead acid batteries in someone's townhouse?

another option is to suggest the customer buy one or more of these units.

https://www.amazon.com/Goal-Zero-Po...TF8&qid=1528906889&sr=8-9&keywords=yeti+power

They are not cheap but one can plug just about anything into it. You would need to come up with some kind of xfer switch arrangement for their gas fired furnace so they can plug into the power station. They can be recharged by solar if you have enough solar PV. But if they are judicious in their use of it they can probably last a day or two with a couple of these units.
Click to expand...

Uhhhh, see post #5?
 
mkgrady said:
I have a customer that asked for a quote for a standby generator for his townhouse condo. I gave him the quote for a 16kw unit. It was going to power his entire load with load shedding relays on the electric oven, dryer and AC. Now he says he does not think the condo board will approve a standby because of the noise during exercising or running during an outage. He is suggesting a battery and an inverter.

My response without any real experience with batteries powering a home is that it would be expensive. He wants me to look into it and I am willing. If nothing comes of it I should still learn something. He has plenty of room in his unfinished basement for batteries.

He is willing to forget about powering all that a 16kw standby could handle. He listed all the critical things that we can all imagine....gas burner for heat system, refrigerator, tv, WiFi, microwave, a few
Lights, etc.. I explained that some of these loads are connected to circuits that supply other than the critical stuff and the system would have to be large enough to power whatever is connected or plugged in.

I’m looking for some feedback on how practical this concept is. I would assume the system would need about 5kw peak load and have an average output of 2kw. These numbers are just shooting from the hip. If these numbers are anywhere near close, how big of a battery would I need to survive a power outage for four days?

My gut tells me the battery bank would be enormous, the inverter battery charger would cost a fortune and I’m not sure what the transfer equipment would be. Anybody have opinions on this?
Click to expand...

We supplied some UPS systems for emergency egress lighting for public buildings like cinemas. Typically, these were 30kVA, 3-hour units in accordance with the cinematic code of practice here. The 30kVA rating was at 0.8PF so 24kW. Or 72kWh energy storage. The batteries were Yuasa and assembled as a bank on site in their own dedicated switch room. IIRC, they total weight was around one tonne.

It is close to what you might require. The costs were in the orders of tens of £k.
 
gar said:
I also believe everyone should have a backup generator.
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Unless you are talking about the Zombie Apocalypse, why? At my house over the last 10-15 years the power has been out for a total of maybe three hours. A generator would be a waste of money for me.
 
ggunn said:
Unless you are talking about the Zombie Apocalypse, why? At my house over the last 10-15 years the power has been out for a total of maybe three hours. A generator would be a waste of money for me.
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Yes, covering for four days continuous power outage seems a bit of a stretch. We have lived in our present house for 12 years. I don't recall one. Even if they had occurred overnight that would have reset some of the clocks.
But then I don't live out in the sticks.........
 
I have lost power for multiple hours a number of times since 1986 when I bought my house. Has not happened since they moved the power lines underground a few years ago. Since then the worst has been an hour or so.

I have not felt the need for a generator although I have considered it.

people who have medical issues like CPAP machines should probably do something about backup power.

I have not done so but I am considering one of the lithium battery power stations so I can run my furnace and hot water heater in case of ice storm. I would not need a lot of juice for either. Maybe one of the small HF generators for the fridge and freezer. I know someone who lives in a Chicago suburb that lost power for 3 days one time right in the middle of a wealthy suburb. A tree fell on some power poles and it took that long to clean up the mess. Fortunately they had access to a small generator that they ran for most of the three days to keep their fridge and freezer cold. Neighbors had to go buy generators. Fortunately only about 20 homes were affected and all of the homeowners were able to get generators except for a couple who were too cheap and just tossed out the contents of their fridges when they warmed up too much. I would not want to miss on showering for three days either.
 
mkgrady said:
I have a customer that asked for a quote for a standby generator for his townhouse condo. I gave him the quote for a 16kw unit. It was going to power his entire load with load shedding relays on the electric oven, dryer and AC. Now he says he does not think the condo board will approve a standby because of the noise during exercising or running during an outage. He is suggesting a battery and an inverter.

My response without any real experience with batteries powering a home is that it would be expensive. He wants me to look into it and I am willing. If nothing comes of it I should still learn something. He has plenty of room in his unfinished basement for batteries.

He is willing to forget about powering all that a 16kw standby could handle. He listed all the critical things that we can all imagine....gas burner for heat system, refrigerator, tv, WiFi, microwave, a few
Lights, etc.. I explained that some of these loads are connected to circuits that supply other than the critical stuff and the system would have to be large enough to power whatever is connected or plugged in.

I’m looking for some feedback on how practical this concept is. I would assume the system would need about 5kw peak load and have an average output of 2kw. These numbers are just shooting from the hip. If these numbers are anywhere near close, how big of a battery would I need to survive a power outage for four days?

My gut tells me the battery bank would be enormous, the inverter battery charger would cost a fortune and I’m not sure what the transfer equipment would be. Anybody have opinions on this?
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I would try to sell him on an interlock kit for the panel and the plug towards the garage door. Run the generator just outside the garage. I don't know if any one would complain about a generator running if the whole complex was out for some reason.
 
GerryB said:
I would try to sell him on an interlock kit for the panel and the plug towards the garage door. Run the generator just outside the garage. I don't know if any one would complain about a generator running if the whole complex was out for some reason.
Click to expand...

We loose power for multiple days about once a year due to winter storms. Happened twice this past March.

The condo prohibits any gasoline or even propane operated equipment. No lawn mowers. No nothing.

I’m thinking I should tell him he should expect to spend 30k or more or forget about it.

I’m not sure it is even safe to charge that many batteries in the basement of a home. Would it need special ventilation?


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mkgrady said:
We loose power for multiple days about once a year due to winter storms. Happened twice this past March.

The condo prohibits any gasoline or even propane operated equipment. No lawn mowers. No nothing.

I’m thinking I should tell him he should expect to spend 30k or more or forget about it.

I’m not sure it is even safe to charge that many batteries in the basement of a home. Would it need special ventilation?


Sent from my iPhone using Tapatalk
Click to expand...

Don't forget about cooling too.
 
mkgrady said:
We loose power for multiple days about once a year due to winter storms. Happened twice this past March.

The condo prohibits any gasoline or even propane operated equipment. No lawn mowers. No nothing.

I’m thinking I should tell him he should expect to spend 30k or more or forget about it.

I’m not sure it is even safe to charge that many batteries in the basement of a home. Would it need special ventilation?


Sent from my iPhone using Tapatalk
Click to expand...
So that rules out any generator. Once you tell him 30k you probably won't need to tell him or "forget about it":D
 
GerryB said:
I would try to sell him on an interlock kit for the panel and the plug towards the garage door. Run the generator just outside the garage. I don't know if any one would complain about a generator running if the whole complex was out for some reason.
Click to expand...
They would all want to come over to the one place that has light, heat, etc.:happyyes:

mkgrady said:
We loose power for multiple days about once a year due to winter storms. Happened twice this past March.

The condo prohibits any gasoline or even propane operated equipment. No lawn mowers. No nothing.

I’m thinking I should tell him he should expect to spend 30k or more or forget about it.

I’m not sure it is even safe to charge that many batteries in the basement of a home. Would it need special ventilation?


Sent from my iPhone using Tapatalk
Click to expand...
If lead acid batteries and they vent anything it will be hydrogen gas - possibly something to be more concerned about then having a few gallons of gasoline stored somewhere on the premises.

Maybe the condo needs to look into some sort of generator to supply the entire place. Don't know how to make the cost fair to everyone, as not everyone necessarily uses even amounts of energy when it is needed.
 
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