Home Backup Power Systems

[BackRoad]

The widespread loss of utility grid power from the recent storm is affecting many, at the same time, whole home backup power (HBP) technology is rapidly advancing.

There have been previous threads on the topic, but wondering if there is any new emerging technology that should be considered looking forward for a 15 year life-cycle solution?

Areas of interest include:

1. What current technology or systems continue to be considered as long-term efficient and reliable?

2. Is there new emerging technology that might be worth considering (such as a Powerwall)?

3. Are there emerging technology or systems that should be avoided?

4. Are there any hybrid solutions using both solar/battery and carbon fuel that are now proven, reliable and affordable for backup power at this point?

 

[ponytug]

The widespread loss of utility grid power from the recent storm is affecting many, at the same time, whole home backup power (HBP) technology is rapidly advancing.

There have been previous threads on the topic, but wondering if there is any new emerging technology that should be considered looking forward for a 15 year life-cycle solution?

Areas of interest include:

1. What current technology or systems continue to be considered as long-term efficient and reliable?

2. Is there new emerging technology that might be worth considering (such as a Powerwall)?

3. Are there emerging technology or systems that should be avoided?

4. Are there any hybrid solutions using both solar/battery and carbon fuel that are now proven, reliable and affordable for backup power at this point?

What do you mean by efficient? I think that is a complicated concept when it comes to energy systems.

I don't think that I have great answers, in part because I think that the decision is very local and personal.

I've been involved in solar and backup systems for most of my life in a variety of roles, both at work and home. At home, we have had solar plus batteries for a while, with generator backup as needed. My observation is, absent tariff and tax changes, that the technologies are getting cheaper, more reliable, and, in the case of battery chemistries and designs, safer. For off the shelf items today, Enphase and Tesla seem to be a big chunk of the US market. We had a backup generator, added solar, then later added batteries, then upgraded the generator and transfer switch. I do not recommend piecemeal. I like the Enphase designs and reliability, but they aren't inexpensive, and while Tesla is pretty cheap, they have little to no commitment to after sales service and warranty support, so if something isn't right, expect months of downtime.

There are a limited number of systems (Enphase, Generac, and DIY ones like the EG4) that support generator plus solar/wind batteries and grid power. We don't have a system that supports generator charging of the batteries, as the use of carbon fuels under prior tax laws wiped out some of the tax credits in the past, making it less popular for grid tie systems manufacturers and customers. Tesla, in particular no longer supports any generator use. If DIY is in the cards, there are more than a few options for solar/batteries (new and used) / inverters. Getting grid tie approval for a DIY may be challenging, depending on your AHJ and utility. I've lived with generators run from methane digesters, which can be done, but weren't in my experience remotely close to low maintenance.

Affordable in my view is likely to be mass market products where the economics of large scale manufacturing lowers the costs, e.g. (Enphase/Generac/Tesla) or DIY. New usually means higher $/kWh, and lower reliability.

As to the next 10-15 years, I find that hard to call as while there are emerging solutions, the actual design for manufacturing and then actually manufacturing something well can take 5-10 years to get to reliable. (E.g. New car models are rarely at their best in the first years of manufacturing.) Personally, the point of backup power to me is that it be reliable, so I, for one, would not be rushing to get the latest and greatest if the intended use was backup power. As an example, one rarely sees solar water heaters where it can freeze, because it is more cost effective to use solar panels to generate power, some of which can be used to generate hot water, either with resistance or heat pump water heaters. It wasn't bad water heating technology, it was installation costs that kept roof top solar water from being adopted.

I would not overlook the other half of the power equation in terms of what can be done to lower the demand by better insulation, windows, more efficient appliances (like heat pump heating and dryers), etc. Lowering the energy demand translates to lower cost backup, systems or longer off grid run times, or some combination thereof. In my experience, where to spend money/invest is a very personal marginal cost/marginal benefit analysis that gets pretty specific to the individual, and the specifics of the site, household, and preferences.

If you want to drill down on particular technologies, and have specific questions, I am happy to share what I've learned.

All the best,

Peter

 

[hayden]

I think the challenge with backup power is..

- It's easy and relatively inexpensive to build a grid-tied solar system, however if the grid goes down, they go down too. So they don't provide any backup.

- You can build a hybrid system with batteries, but they are more complex and batteries add a lot of cost very quickly. So to keep the cost down you have to limit battery size and how long it can provide backup power. They are great for short duration outages, but frankly, short outages are an inconvenience and not really a problem.

- Long outages are where you really need backup, and batteries alone aren't going to get you the time you need without being very expensive for the rare occasion when you need them. This can be offset by adding a generator, but now cost and complexity increase even more.

For better or worse, a whole-house backup generator is often the best solution for a prolonged outage.

 

[BackRoad]

Mr. Peter and Mr. Hayden, great information, very thoughtful responses. I'll circle back and query with some specifics!

Mr,. Peter, "efficient" may not have been the right word! The intent was to mean "minimal hands-on support by the home owner post install" (a dependable solution that keeps my wife in lights and heat if I'm away.)

I've got a couple of very dependable Honda i2200 generators that I can run in series...but I need to be home to make it work, and then move power cords around to keep the freezers and refrigerators happy...so not "efficient", and not even deployed until about hour 6 of a utility outage!

 

[D&D]

The widespread loss of utility grid power from the recent storm is affecting many, at the same time, whole home backup power (HBP) technology is rapidly advancing.

There have been previous threads on the topic, but wondering if there is any new emerging technology that should be considered looking forward for a 15 year life-cycle solution?

Areas of interest include:

1. What current technology or systems continue to be considered as long-term efficient and reliable?

2. Is there new emerging technology that might be worth considering (such as a Powerwall)?

3. Are there emerging technology or systems that should be avoided?

4. Are there any hybrid solutions using both solar/battery and carbon fuel that are now proven, reliable and affordable for backup power at this point?

I’ve been up and down on this same issue. Whole house generators are nice but picking the right one can be difficult. Do you really need a 22kw or can you conserve some and get by with a 10kw? Fuel of choice, diesel or lp (no natural gas at farm)
Battery maybe the better way to go but I haven’t checked with my insurance carrier yet.
The new E10 from ankersolix looks promising and comes in about the same price range. Solar compatible, 200 amp switch, multi fuel generator interconnect

https://www.ankersolix.com/whole-home-backup-power-solution?ref=naviMenu_2_1_1_img&_gl=1*1yg8fnt*_up*MQ..*_gs*MQ..*_ga*ODgyMTEzODgzLjE3Njk0MDI4NjE.*_ga_79741PKWEG*czE3Njk1MzE2ODQkbzMkZzAkdDE3Njk1MzE2ODQkajYwJGwwJGgwJGRBOTFuU2JqTkNjOXFSNVA2cXBadWFwS3BJQzVtZlNWeS1R*_ga_Y09L4XMTTK*czE3Njk1MzE2ODQkbzMkZzAkdDE3Njk1MzE2ODQkajYwJGwwJGgwJGRpR2NScHF5VWVEZnNBZ0VTX2VGUlFVRUdMMk95YVBVcjJ3&gclid=Cj0KCQiA4eHLBhCzARIsAJ2NZoLFx1JJoLHK0mg0h5iiKiKnClLIRK5fuwG1HUlI9rdCyZjF5QRsIa4aAqM_EALw_wcB&gbraid=0AAAAABVgOKku6QruY9yjmaewoYWdlKjRu

 

[ponytug]

@BackRoad thanks for clarifying efficient. For ease of use, I think a whole house generator with auto start and an automatic transfer switch is hard to beat. Add a few UPS units to tide over internet and TV, and chances are nobody will really know the power is out. I personally would fork out the cash to put the generator quite aways from the house. No whole house generator is exactly silent, though it is my perception that many of the liquid cooled versions tend to be a bit quieter. If your backup generator would be on propane, factor in a separate tank, and your worst case winter temperature, and the accessible volume at that temperature with the generator running at load. That capacity will be much smaller, so to cover an extended winter outage, you might need a tank much larger than you would expect. Just run the numbers, and check the factory guidelines. Putting the propane tank below ground helps a lot, but that's not usually cheap, and not everyone wants the tank underground.

@D&D +1 on checking with your insurer with respect to solar/batteries/generators/wiring. I think that these aren't zero risk items, and I want my insurer to back us up if there is an issue. I would not put lithium batteries in, or on a building for fire reasons. The lack of predicability of lithium battery fires is my main concern.

All the best,

Peter

 

[ericm979]

My neighors in California built an ADU a few years back. They designed it to handle the frequent and long outages we had there. They have solar, battery and a generator input. During an outage even in winter the solar charges the battery enough that they only need to run a portable generator a few hours a day to top the battery up.

When we built our new house in Oregon we did the same only scaled up for a larger all electric house.

With the batteries you don't need to size the generator so that it can handle all possible loads, only to run at 1/4 capacity 90% of the time. That's pretty inefficient.

So far we have not had an outage at this house. But looking at the power consumption numbers I can easily use my 5kw Honda generator to keep the batteries topped off. We may have to turn down the mini splits but that's what the wood stove is for.

It's not the most cost effective solution. The batteries cost roughly another 50% over a whole house generator, though prices are falling. Using a portable generator like we did in California costs even less but would not work with an all electric house.

 

[TractorGunn]

The widespread loss of utility grid power from the recent storm is affecting many, at the same time, whole home backup power (HBP) technology is rapidly advancing.

There have been previous threads on the topic, but wondering if there is any new emerging technology that should be considered looking forward for a 15 year life-cycle solution?

Areas of interest include:

1. What current technology or systems continue to be considered as long-term efficient and reliable?

2. Is there new emerging technology that might be worth considering (such as a Powerwall)?

3. Are there emerging technology or systems that should be avoided?

4. Are there any hybrid solutions using both solar/battery and carbon fuel that are now proven, reliable and affordable for backup power at this point?

I'm not sure about anything new that is viable.

Options are a generator (which we have, Generac 22kw, on a 5500 sq. ft. house. This is like being plugged into the grid. Uses aout 2-3 gallons of propane an hour.

PW3 stores 13.5 kWh of energy. A typical home uses 30-60 kWh in a day. Doing the math for long term power outages, having several batteries is a small fortune. Having solar to charge them is another cost. An 8kWh system will charge a PW3 in just under 3 hours.

 

[MH8675309]

I've often thought that if the power went out for an extended period it would make sense to use the generator sparingly. Enough to pressure up the well and maybe heat some water - hot water tanks will stay reasonably warm for a few days. A faraday cover is not a bad idea for the generator - EMP protection. An alternate source of heat would be all the less the generator would have to do. And its good to have options

 

[ultrarunner]

Soft Start for some larger motor loads might allow for lower peak useage?

It does seem overkill to have a system that can handle everything at anytime unless money is no object.

Peak electric demand can be further reduced or offset with propane or natural gas or even wood…

 

[Carl_NH]

We did our system piecemeal - most $$ without foresight into new technology.
- 1996 portable generator 5000W plug in power cords to run key circuits
- 2009 installed 90% efficient oil boiler, HW baseboard heat and DHW (no natural gas here)
- 2010 portable generator 8000W - back feed panel to run everything
- 2014 installed 7.2KW Solar used portable generator in outages as solar was off by design
- 2017 Installed Mini splits for AC (replace window units) and for supplemental heat.
- 2024 installed whole house generator - still Solar disconnects during outages (8KW generator was free) cost $6500 to install with new LP tank, transfer switch etc.)

Doing it all over again;
- Would still do solar if it works at your site
- Then add battery with solar (the Anker indicates $9K to run our house for 18 hrs. as most outages only last 2-6 hours

If you don't have solar, then as others have said, just install a whole house generator to support the critical loads. 8KW will do our house 3200 SF just fine as the heaviest load is the 1.5 HP water pump

 

[ponytug]

Soft Start for some larger motor loads might allow for lower peak useage?

It does seem overkill to have a system that can handle everything at anytime unless money is no object.

Peak electric demand can be further reduced or offset with propane or natural gas or even wood…

A soft start helps some things, but the aggregate daily load is usually the issue as @ericm979 and @TractorGunn point out.

The tough bit is for many owner how to handle heating during an extended winter outage. Wood, and propane both do well in extended outages, but propane directly to heat beats propane to electricity for resistance heating, though modern heat pumps run on propane can come close to it. Heating oil may be an option for some parts of the country.

Generators do best at about 80% load (gross generalization, but there is a Goldilocks region for all of them) so going big brings on issues if the owners don't periodically run it at maximum, or close to maximum loads. Most residential backup generators don't include full power sized load banks to periodically stress the generator. Batteries definitely help a generator run at its sweet spot, for fewer hours.

Here, during a winter storm, solar is useless, so the batteries slow lose capacity over an extended winter (or fire) outage. I'd love to charge the batteries, but not to the point of ripping out a working system in favor of a better one. My personal bet is that in a few years enough kinks will be out of vehicle to home (V2H) for us to rely on that, if push came to shove.

We have solar plus batteries with non-integrated whole house generator (manual transfer switch), but would not be cheap to do it now, nor simple (or "efficient" in backroads' desire). But all of us here can do it in a pinch. In contrast a neighbor has no solar, no batteries, a bunch of heat pumps and a propane generator large enough to handle it all. It works for them, and is both simple, and in the grand scheme of things inexpensive, though there are complexities to what they installed.

@MH8675309 Side note on EMP: a faraday cage is not a panacea for EMP protection, and there are more than a few nuances to improving EMP resistance for electrical devices, generators in particular, and what type of EMP you are trying to protect against matters. Based on what I read on line, there is a bunch of misinformation out there. I suspect @WinterDeere has some personal insights.

All the best,

Peter

 

[edgarrian]

I really like our whole house generator (Generac) We've had it for 8 years now. I maintain it myself. I honestly dont see other resources being as good. We have had power outages only last 20 minutes or so. But we have occasionally lost it for 8 to 10 hours. Once during my wife's birthday party during the summer. Game changer. Im not sure there will be anything more effective than these in the next 10 years. Maybe with AI coming on strong there could be some adaptive technology to go along with whole house generators. That would be the area i see coming

 

[kenmac]

In the long run and for simplicity of it all. It's hard to beat a whole house back up generator. I just had one installed.
I have NG available which is nice not having to worry about a propane tank to keep filled, or running out. As long as they are supplying NG, I'm good.

When the grid goes down, I believe within 15 seconds the Generac fires up and supplies power to the home and shop. That's hard to beat !

Someone mentioned about noise with a stand by generator. I can tell you this 35KW liquid cooled I have isn't loud at all. We could stand by it while it's running and have a conversation in normal voice.
I have heard the air cooled whole house generators sound like a loud lawnmower. I didn't want that , so I opted for a liquid cooled with insulated housing

 

[TractorGunn]

I really like our whole house generator (Generac) We've had it for 8 years now. I maintain it myself. I honestly dont see other resources being as good. We have had power outages only last 20 minutes or so. But we have occasionally lost it for 8 to 10 hours. Once during my wife's birthday party during the summer. Game changer. Im not sure there will be anything more effective than these in the next 10 years. Maybe with AI coming on strong there could be some adaptive technology to go along with whole house generators. That would be the area i see coming

We've had ours for that long as well. Easy to maintenance too.

 

[BackRoad]

Valuable...very valuable! Just thinking out loud based on the guidance...

It's shaping to be a kind of Apollo 13 mission. Put all the pieces on the table and see what solutions can be created.

As several have stated, a key input seems to be identifying the variables and load demands unique to a specific home...then maybe the next step is to simplify what's trying to be solutioned.

I have natural gas piped into the house for the kitchen range and boiler for radiant floor heat. I did include a spare natural gas shutoff already plumbed to potentially feed an external generator (a plus).

Another variable is having a high efficiency wood burning fireplace that will output sufficient heat to sustain living in the main area of the house in winter if needed with no a/c (a plus).

In an extended outage, the top tier load would be for freezers and refrigerators with periodic need for the well pump.

The second tier critical load would likely be the minimal power required to operate the natural gas powered boiler used for radiant floor heat specifically in the winter.

The third tier load starts getting into creature comforts such as lights, communications, device battery recharging, microwave, etc.

Potentially based on the expected "normal and routine" short duration utility power loss (meaning it is expected to be back to normal within 24 hours), simplifying the solution, such as a "right sized" natural gas genset with auto transfer would be the logical and most simple solution initially.

Unless one is going fully off grid, feeding excess solar generated power back to the grid has not proven to be cost effective with the co-op we are on, nevertheless, I get into deeper water when I start considering "black swan" utility events.

Meaning those hopefully very rare situations with potentially no natural gas, and the utility grid is expected to be down for a week or longer. That's where I'm drawn into thinking of some type of home solar/battery solution.

Thinking about it all, perhaps those rare catastrophic "everything is down" events might be more effectively managed by temporarily moving into the four season RV which already has solar/batteries and a portable genset?!! Periodic power to the freezers in the garage would be the only extra manual action that might be needed...hmmmm...

It seems the availability of natural gas is the key determining factor.

Thank You gentlemen! Your contributions have been hugely helpful!

Simplify...simplify...simplify...

 

[sd455dan]

I always wanted power back up we got by with a 2 KW Harbor freight Inverter powered by the tractor then a gas 6500 watt generator.

Jumped in to solar before really researching enough, have 25KW of solar panels up and a 12KW Hybrid inverter. 87KWH of batteries
If just back up for a power outage is the plan , I agree with the guys saying just buy a quality generator.

 

[kenmac]

I have natural gas piped into the house for the kitchen range and boiler for radiant floor heat. I did include a spare natural gas shutoff already plumbed to potentially feed an external generator (a plus).

Depending on the size generator you select for your needs, that spare shut off and line, likely won't be large enough to supply enough gas to run the generator.
I did the calculations for my generator, and I needed a larger NG regulator with larger orifice, and a larger supply line to the generator.