Learn Me: Whole-Home Generators vs Solar and other options

In reply to 84FSP :

And now you're back to my thinking. The array is there for other reasons. What's the minimum amount of extra hardware to bring that array back online if the grid goes down? I'm thinking some sort of grid forming hybrid inverter with enough battery to form the grid.
Like this with a minimal battery: https://regenpower.com/articles/hybrid-inverter-vs-off-grid-inverter/

I sold emergency generators for a living for 25 years and if we're in the OP's position now, I would go with solar and batteries. Zero questions.

Yes solar/batteries are more up front but you get: reduced utility bills all the time, can sell excess power back to save even more, unlimited backup power, free charging of an EV (when the same outage at your home may have also taken down public charging) and no noise or smell.

Generators require far, far more maintenance than solar/inverters/batteries. The cost of maintenance over 10 years would surpass the cost of a solar battery replacement and realistically, in a standby emergency application, the batteries will last WAY more than 10 years.

Solar works fine with or without the utility connected. Not an issue.

You can use an EV to back feed the house with the right equipment but IMO, it's pretty stupid. In the OP's situation where there's been no power for days he'd have drained the car batt and then have no transportation. 
 

67LS1, grid-tied residential solar installs are designed to shut down when the grid is down. They need the grid to form the AC signal. So it doesn't work without a utility connected unless it is specifically designed to do so.

I think the EV storage idea is good and bad. 

Good:

• you can use your backup battery like a car the rest of the time :)
• if the outage is of a suitable size, you can drive to a public charging spot and refill your battery

Bad:

• when the car leaves, so does the power
• if you cannot drive to a charger and you don't pay attention during an very extended outage, you can strand yourself

Note that a single Tesla Powerwall is 13.5 kWh. An F150 Lightning - which has the ability to feed the house - has at least 98 kWh of capacity. Those EV batteries are big.

84FSP said:

In reply to BlindPirate :

This is my understanding as well and jsut seems silly to be an actual issue.  Wouldn't a handful of lead acid batteries and a grid disconnect sort this out pretty easily?  I hate the idea of not being able to use a pwoer source when it's most needed.

In principle yes, in practice there are a lot of details to sort out and it adds a lot of cost to the system.  You need a "smarter" inverter, and you need batteries that supply enough current to make power that the house is drawing.  Sure, you may decide you only want to run a small amount of stuff when the power fails, but how do you tell the inverter that?  Most people would want the system to automatically switch over, but if the current load when the power fails is too high then that's a recipe for an instant brown-out.  So there's a minimum battery capacity, and even so you're probably going to need to install a sub-panel and move all of the protected circuits to it.  That's a lot of electrician time to do rewiring, holes cut in walls, drywall repair, etc, etc.

There's also a lot of cost involved in the power company certification around the automatic grid disconnect.  You can't DIY that because they're worried about the safety of their repair crews.

One guy I know looked into it and it added $10-15K to the cost of a $20K system.  Obviously the details are going to vary a lot but it's not an insignificant addition, which is why most household systems don't have it.

Keith Tanner said:

67LS1, grid-tied residential solar installs are designed to shut down when the grid is down. They need the grid to form the AC signal. So it doesn't work without a utility connected unless it is specifically designed to do so.

I think the EV storage idea is good and bad. 

Good:

• you can use your backup battery like a car the rest of the time :)
• if the outage is of a suitable size, you can drive to a public charging spot and refill your battery

Bad:

• when the car leaves, so does the power
• if you cannot drive to a charger and you don't pay attention during an very extended outage, you can strand yourself

Note that a single Tesla Powerwall is 13.5 kWh. An F150 Lightning - which has the ability to feed the house - has at least 98 kWh of capacity. Those EV batteries are big.

 

If your buying a solar system with batteries, 99.9% sure it would include automatic switching to/from "Island" mode. It's one of the systems biggest selling points.

Yes, Tesla power walls are smaller than vehicle batteries so depending on your wants/needs/current budget you can buy one or more batteries and add additional capacity at any point in the future.

In reply to 67LS1 :

It's the "with batteries" part that's important in that statement. Batteries have a big effect on the cost of a solar install and are not required for a grid-tied system. So simply saying "solar" doesn't necessarily imply "with batteries", it should be stated explicitly. 

In reply to 67LS1 :

Interesting- thanks for that info, I haven't had any idea of what the upkeep/maintenance costs of the generator would be and that will definitely be something that I'll press the contractor on when they come to give me an estimate. 

Somewhat ironically, for a while (last year I believe) I got like 5 calls in a month about getting an estimate for a solar install at our house, and now that I've actually requested one I've heard nothing from them. 

The EV-powered option is an interesting one, but since I don't thing we're likely to be buying one in the really near future (my wife's truck is less than a year old, and hopefully my QX4 won't be kicking the bucket anytime soon since I've not seen any full-electric replacement for it that I've really liked) is not something I'm really considering. When we design and build a place down the line (guessing like 10 years from now) it will likely be a different story- but I imagine EV charging (and possibly potential house-powering) will be pretty standard at that point.

Oddly enough, the eventual move to an EV is one reason I do want a NG generator.  It would be sized to be able to charge the EV in the event of an extended power outage. But like the OP, there isn't an EV that meets my needs right now, so this is not high on the priority list.

Looking at the data I can google-up for NG generator maintenance (along with my own knowledge of spec'ing and installing commercial versions for 25+ years), I can't see how a home-sized generator would require a lot of expensive maintenance.  It's another engine to keep track of, yes.  But it's basically an oil change, a few filters and keeping the enclosure and general area clean. 

We put an LP powered Generac  unit in at the vet clinic a couple of years ago. 24 kW, which was the largest available before making the leap from air cooled to liquid cooled, which comes at a significant cost. 
 

Looks like the maintenance agreement on it runs at about $200/yr, plus about another $50/yr for a subscription for it connecting to Generac's app/server for status and automated maintenance reporting. 

Still have the appointment for the quote for the generator on Friday. Got a call from whatever Angie's list is called now which is apparently where the request for a solar quote went to. Friendly guy there goes to look up recommended solar installers here to contact directly- and was clearly shocked when his query came back with no results. So going directly through the website of a few local places to request quotes. 

Ashyukun (Robert) said:

In reply to trucke :

Thanks, that's good to know! Having to run the gas line to wherever the generator will be is something I hadn't considered, given we'd likely want the generator closer to the electrical panel which is around the house from the regulator (and away from our bedroom window). We'd likely have to go with getting an additional panel for it too since our house is like 60 years old and while the electric was upgraded somewhat when it was remodeled about a decade ago there adding it in directly likely won't work.

How bad is it noise-wise when it's running? Have you had to use it much?

Noise is very low.  I hear the neighbors generator slightly as that one is on the bedroom and family room side of our house.   We have not had power outages in the North Carolina mountains this year so not uch use.  Hence, expensive insurance.  It does run every Monday to test and ensure the battery stays charged.  As we get older, we will be glad we made the investment.

The gas company can route the gas line around the house with very little damage to the lawn.  Pretty amazing how they do it.  That ran about $2,700.  The electrical was a bit more because of the old panel we had.

I've got solar with a power wall battery. We don't lose power often but when we do, I haven't even noticed. If I lived in an area where we lost it often the only other thing I'd do is get the f150 hybrid with 7.2kw bed power. Our house ends up being net zero for the year but the winter we are negative and summer well positive. Maintenance is clearing the roof of detritus and rinsing the panels. 
'If you have the power wall set in storm watch mode it will charge fully in advance of the storm. Then if we don't use a/c or high draw appliances we can pretty well go indefinitely- obviously pending cloudiness. 
 

With the battery, we can run regardless of grid status. I thought it was stupid when we bought it but I sorta dig it now. 

In reply to Teh E36 M3 :

Thanks for the info- I was thinking that would be how things would work with a battery in the setup. Do you know what your average monthly usage is? I'm curious how it compares to ours, especially since I would have to guess that we'd be getting moderately less sun here in north-central KY than your are in CA (though you are in northern CA, so they may be roughly equivalent).

In reply to trucke :

I wouldn't be too worried about tearing up the lawn, the interesting thing would be that running the line from where our gas meter is to around where I'd expect them to put the generator would be going over the door from the basement walkup. The contractor may have a different idea as to where the best place to put it would be, we'll see.

In reply to Ashyukun (Robert) :

You are likely having a hard time finding solar contractors because electricity is cheap where you live. Not a lot of demand due to the incredibly long pay back. The average in Kentucky is 13 years, CA is 6. Generally, the higher your useage, the shorter the payback, the lower, the longer Vs. the average for your area. Batteries add years to the payback, unless you have time of use charges. Without time of use being an issue- a generator beats batteries, hands down. Don't let the solar part confuse the situation. You can install a battery without solar instead of a generator. But you wouldn't, because the cost/reserve capacity is better with the generator, especially for extended outages.  

A plumber will use a trencher or mini-ex to run the line. A trencher will be easier on the lawn, for sure. 

Gas utilities use horizontal drills for service lines, but this is after the meter. 

I've seen some cases where people will run gas lines off their house line in the basement out to the generator. It's a mucher larger line, though, so it depends on what you've got plumbed already. 

So I filled out request for quote forms on two local Solar company sites, and one called me up just before the end of the day. They needed some pictures of the current state of the tree in our front yard that will partially block the front (south-facing) roof since the sat pictures were from 5 years ago and it's both grown and been trimmed, but gave me some general ideas of the costs. 

First off, depending on how much of the roof they can use, they may only be able to put up an array capable of generating about 1/3 of our max power usage so that will heavily influence things. For -just- the panel setup (no batteries) they said it would be around $15k; adding a (I'm thinking only one, though 2 might be more appropriate) PowerWall roughly doubles the cost. Apparently there's about a $9k tax credit, though I think that's essentially a 'knock $9k off what you report for income and thus pay taxes on' vs. $9k in our pockets. 

There is apparently a campaign going on now locally with the backing of the city to get more houses on Solar, so that may help things as well- will have to see what the formal quote comes back as. 

Ashyukun (Robert) said:

In reply to Teh E36 M3 :

I'm curious how it compares to ours, especially since I would have to guess that we'd be getting moderately less sun here in north-central KY than your are in CA (though you are in northern CA, so they may be roughly equivalent).

On an average annual basis, it looks like Central KY sees enough solar energy to generate about 4-4.5 kwh per sq meter of panels per day. Northern CA has a lot more variability depending on exact location, but generally gets enough sun to generate 5-6kwh/sq meter/day:

The maps above are annual averages. If you break it down by month, pretty much everybody gets adequate sun during peak summer times, and most of the US struggles during the winter. It's just that places with lower annual averages have less energy available during shoulder seasons. Peak production season is shorter in other words.

So, if you have electric AC in use during warm months, but NG/propane heat during cooler months it might be more about time of year and usage than average annual output. You'd essentially only be buying it for summer months, but the lower production in winter months might not be a deal breaker if you're not entirely electric. A lack of tax incentives and/or net metering will really hurt the payback period though.

Is there a good resource on the web one could use to look at their area more specifically regarding solar? Incentives, net metering, available irradiance, etc? We may be in our house a bit longer than expected so I'm back to thinking about solar - especially if one of our next DDs is an EV.

So got the detailed proposal from the solar place this morning- the salient info is all essentially shown in the image below:

It's worth noting though that the 'net cost' is a bit misleading because, at least as I understand it, the roughly $9600 Solar Tax Credit is a 'we knock this amount off your reported income' vs. 'you have to pay this much less in taxes'. I'd be happy to be wrong though. Assuming it is just coming off of income it would mean more like ~$2500 or so in actual money so the actual total cost would be just under $30k (total is about $32k, minus the $2.5k for the credit).

It is rather interesting to see right up front that it's not expected to recoup the initial cost over the lifetime of the system- at least with the battery. As previously noted, not getting the PowerWall roughly halves the cost and the 'net cost' is about $11k with the same (understandably) just under $15k lifetime electric bill savings, but makes it a lot less appealing for what I want (as if the power goes out then without the battery the solar is only helpful during the day).

It will be interesting to see what happens with the gas generator estimate tomorrow. I expect that the cost of that will be much lower- probably on par with the 'net cost' of the solar without the battery- but as previously noted, it would be entirely 'sunk cost' vs. offsetting some of the cost over its life like the solar would. After however long of a time that they're counting as the 'lifetime' of the solar system it would in the end cost about the same as what I'm expecting the generator would cost.

EDIT: Some quick googling yielded that the tax credit does appear to be a direct reduction of what you owe- so a $9500 tax credit would mean we'd owe $9500 less in taxes (and thus would likely get quite a large refund). So, the 'net cost' is probably closer to accurate than initially noted, and over the lifetime would (in theory) cost less than the generator.

So, the contractor from Generac came by this morning and looked things over and gave us a quote for the natural-gas whole-home backup generator. Since we have primarily natural gas appliances and use electricity for very little of heating anything up even (apparently) keeping the hot tub at temperature (but not running it with the pumps on high) a 18kW unit was apparently all that was necessary. The costs came down to about $6k for the generator & battery, $4k for the install & inspections, and $500 in taxes for a total of $10,500. There's a promotion running until mid-April where the warranty is extended to 10 years from the standard 7, but presumably we would have to have the basic maintenance on the generator done by the contractor to the tune of $230/year. If we wanted the remote monitoring by the company as well it would be $50/year after the first free year of it. 

So assuming that we wanted to have all of the maintenance done by contractor and have the remote monitoring, over 10 years the total cost (not including the natural gas it would use) regardless of whether it was ever actually used would be $13,300. Extrapolating that out to 25 years (since that's what the solar quote uses for savings over the 'life' of the system) and assuming the maintenance and monitoring rates didn't go up, it would be $17,500.

So, comparing the 2 practical options (the theoretical 3rd- solar with no battery- would be kind of pointless for my intents...):

(note: this assumes no maintenance cost for the solar, which it shouldn't need unless there is physical damage, and doesn't account for degradation of the batteries and does not include NG usage by the generator).

So- from a purely financial standpoint, in the shorter-term (which is fairly reasonable considering we know we won't be in this house forever, I'm guessing about 10 years max) the generator is the more cost-effective option... and also has the advantage of likely being able to physically take the generator (which is over half the cost of the system) with us to a new house, assuming it would be sufficient for it. Of course, the generator a) provides nothing in return if we never have another power outage and b) would be useless if something happened that interrupted the gas service. Conversely, the solar setup would be offsetting our electric bill by a bit each month and shy of a nuclear winter should provide at least some power regardless of what is happening anywhere off of our property.

It will be interesting to see what The Dancer thinks about all of this- she was there when the generator guy gave us the quote, but hasn't seen the solar yet. 

There's also the question of whether any of this makes any sense since we know we're not going to be here indefinitely- and in theory the outage we had a few weeks back would be a once-in-a-decade occurrence... in which case it would make more sense to do neither and either figure we can deal with it like we did this last time or do something like get one of the transfer panels mentioned earlier such that we could hook the existing generator up and power certain circuits in the house (like the furnace- I don't think our HF generator could handle the AC though) in the event of a longer outage.

Those numbers for the solar are horrible. Your primary concern is back up power, right? So ignore the method and separate it from the solar, and see if the solar  stands on it's own. You are basically using your solar investment to pay for your generator over time. You could buy solar and a generator and the payback would work the same way as solar and a battery, there is nothing special about the battery that saves you money. 
 

Let's take your generator for $10,500, and put the $12000 difference into a mutual fund instead of a horrible ROI solar system. At 7%, your mutual fund is over $75000 at 25 years, you are almost $60k in the plus vs. just breaking even with the solar. And the money is a lot easier to take with you when you move. 
 

Edit- unless you foresee some drastic changes to your energy bills on the horizon. They would need to be quite substantial to offset the difference. 

In reply to Boost_Crazy :

You're making the assumption this would be a cash purchase, so you're thinking of other things to do with the money. If it's financed, though, that changes the math. Our array is financed and we're saving money every month right from the start - money that we can put into other investments or pay off other obligations.

I'm going to say about $10k of that solar estimate is battery, as I'm pretty sure that's about the price of a Powerwall. So the battery is roughly the same cost as the generator. The difference is that the battery can help the solar offset some electricity cost by time-shifting the solar power, so it's working for you all the time. 

Note that a Powerwall takes the load in a power outage in 100ms, so you might not even notice. No need to wait for a genny to kick in and restart every computer in the house. The generator will theoretically run forever with the assumption that the natural gas will keep flowing, the battery might require you to do a little energy management depending on the array output. But it's truly independent, it doesn't rely on any outside source to operate.

You can also take a battery with you when you move. Of the three (panels, generator, battery) it's probably the easiest to take. 

In reply to Keith Tanner :

Did you look at his electricity cost? He's paying almost nothing. His goal isn't solar, his goal is emergency backup. Solar sales people try to connect solar with battery backup when they don't need to be. Ignore the battery, the solar itself has a ridiculous payback. It doesn't matter if it's cash or financed, he's still paying for it, and there are a number of ways he could invest his money more wisely. When you break it down for most people, solar is an investment, to reduce their carbon footprint, or a bit of both. But for most, the investment part is a huge part of it. In this case, it's a poor investment, period. I was just pointing out there are much better ways to pay for the emergency backup. 

I talked about time of use benefits of batteries in my previous posts. I'm pretty sure it doesn't apply in this application, and his rates are so low, it really doesn't matter that much. The one caveat being future changes. If Kentucky gets a case of Californiaitis, that might change in the next 20 years. As for the quick changeover- get a cheap UPS for anything critical, most people won't care if their lights blink or their fridge stops for a coupe seconds. I had this same conversation with a large company that wanted back up power for an office building. They wanted enough battery to run the building for a few hours. It was much, much cheaper to go with a few hundred thousand dollars worth of generator and a large UPS. 
 

I don't see what his electricity cost is specifically. But I see a quote for a (roughly) $11k system and a (roughly) $11k backup, along with another quote for an $11k generator. Let's separate those.

Array: Sure, he's paying for the array. But he's going to pay SOMETHING for electricity no matter where it comes from. Shifting some of your electricity payments over to paying for an array has the potential to lower your overall monthly costs with the eventual goal of zeroing out the solar part of it eventually. You can't invest money you have to spend on something else. The numbers have to work but they can work even when electricity is cheap. I know this because I see those numbers myself.

If you can make the math work for the solar, then the math for the generator vs battery shifts as well. That $11k bill for either a generator or a battery becomes a direct comparison. The battery doesn't need annual maintenance and monitoring costs that will more than double the cost of the unit over the next decade. It doesn't need supplementary UPS batteries for all the various things you don't want randomly shutting down, like a work computer or networking hardware - both of which run standalone UPS batteries at my house. It has the ability to make the solar math work better so there's some synergy there - that ability depends on the utility's arrangements with solar generators.

All of them are long term plans, I'll admit. If you're planning on moving, any sort of infrastructure is going to have some lost costs. In that case, just buy a Honda generator and park it in the back of the garage with the expectation that you won't be running the full American Lifestyle until the grid comes back. It'll keep your food cold and the house temperature at a survivable level, which is all you really need.