How to start with a residential system using solar, battery, and generator

[r1559]

Hello, first wanted to take a moment to thank everyone on this form for the great information and professionalism I've come to know.

I have a newbie question about planning a system in the Santa Cruz mountains of California, making the best use of a generator, energy from solar, and a battery (when I say battery, I mean a battery of batteries / power wall / whatever you want to call it).

We have what, to me, is a complicated scenario that requires some good system planning. As an example, we have maybe 4-5 times during the summer, a 2-5 day power outage during clear, sunny weather. This is either due to rolling grid power outages due to the extreme fire danger, or because we're at the end of a power line that runs up a very steep and densely forested canyon that is very prone to deadfall. In the winter, we have frequent big storms that destroy grid equipment. It is normal to have 2-3 outages during the winter that last 5-8 days, with no sunlight to produce solar energy.

I did a really nice power system for my RV so I know a thing or two about solar, battery, and 'shore' power; as such, I'm stepping back from this and I want to pay a professional to plan and install the system. The RV was fun but planning a system for my house with the crazy weather we have is above my pay grade.

I would love to hear from you guys about how to get this project rolling. I had an electrician & certified Generac dealer come out a while back and want to sell us a 20kW propane generator. I've put in some calls to a few local solar companies who haven't bothered to call me back in months. And just now I put in a profile on EnergySage and am flooded with quotes for large NON-local solar companies who seem ready to come out, slap some panels on my roof, and run away.

Are my needs simple enough that a decent solar installer can plan and install it? Do these companies also work with generators, or is that a "oh you'll have to call Generac and let us know once it's installed" kind of thing. Is it a thing, to find and hire an independent solar planning consultant who understands the local weather and situation, and can manage the work done by a solar installation company? I guess I really don't know where to start with this.

 

[kommando]

Start with your usage profile by season and a daily hour by hour, then sort out how much PV you can install and the likely generation profile again by season and hour by hour. Couple that with your requirement to cover a 5 day outage to size the battery and see what the required system looks like.

PV production database

https://pvwatts.nrel.gov/

 

[DIYrich]

One option is go to Sol-ark's website and use their search tool to find an installer near you. Seems like your use case needs a very reliable system. It is easy to integrate a generac whole house generator whether they do it, or the generac installer. Or you can go the cheap generator and chargeverter route.

 

[Q-Dog]

If you have enough solar to cover daily usage, plus a generator, you don't really need a huge battery that can cover a multiple day outage. The solar recharges the battery every day, and the generator is there for backup when the sun doesn't shine. Or in your case, most of the time the grid is your backup to the solar and the generator is there for power outages only when the sun doesn't shine.

I feel like if you build a system with a large enough battery to cover your use for 5 days, you are really close to a system that will cover 100% of your usage. These days the solar panels are the cheapest part of the system, so really easy to install enough panels to cover one day usage.

 

[Madcodger]

My thinking is closer to,@Quattrohead. Personally, I don't think you need as much battery as most people are saying. If outages happen only 2-3 times per season, you can have enough battery to run just 2-3 days (not 5-8), and use the generator to recharge DURING the outage, assuming you can keep a fair amount of propane on hand to fuel the generator. Even for normal system sizing around winter solstice, people often install battery banks sized to last for several days of low-no sun. It might be more economical to have less battery for just those times, with a good ability to recharge a smaller bank more often.

 

[OffGridForGood]

I think the OP should DIY the design and installation with our help.
After all, they did a mobile system already, just need to take the plunge. We will help.

 

[r1559]

Start with your usage profile by season and a daily hour by hour

I was afraid someone was going to say that. Some of the critical systems are difficult to profile. For example, while I do know the amperage and wattage of the well pump and booster pumps, I don't really have a good idea of how frequently they run. Similarly with the propane tankless hot water heater -- I'm not clear how long it runs or how frequently. Are there some standard tables that can help me estimate this? I don't want to go down a rabbit hole and put a meter on each device and take measurements for an entire year to come up with a perfect profile, because this needs to happen sooner than later. I'd rather have a conservative estimate today, than a perfect metric in 6 months, for these kinds of systems.

I also noticed that "Energy Audit and sizing tool Rev B" doesn't have a way to differentiate "critical" vs "very important" vs "nice to have" systems. The well water system is critical. The hot water heaters are nice-to-have. I'm not exactly sure how to approach this.

If you have enough solar to cover daily usage, plus a generator, you don't really need a huge battery that can cover a multiple day outage.

Good point about Battery. It's the one area I worry about as a long-term investment because of its expense, the risk of newer & better battery technology showing up soon after I've made an investment, the lifetime of a battery, and the environmental impact once those batteries need to be replaced.

assuming you can keep a fair amount of propane on hand to fuel the generator

So yes, running the generator is a concern.

Propane availability is a problem. Normally it takes 2-3 weeks to get my 325-gallon propane tank (which is also used for water heater and, sometimes, forced air heat) refilled. If we are in the middle of a 7-day power outage due to a huge storm, there is going to be competition to acquire propane, and likely shortages, making it effectively impossible to get propane.

I've heard that generators can run on diesel, but those might be only the smaller-duty generators? Nobody I've talked to about large 15 and 20 kW generators has mentioned diesel, but I'm not sure if it's because they are swayed by manufacture preference. Does anyone know? Diesel is certainly much more readily available, even during a huge storm, although transporting it would require a truck-mounted tank and pump which is a nontrivial expense.

Speaking of expense, I do not know if diesel or propane is more efficient when using a generator for producing watts.

If anyone has input on these generator questions, I'd appreciate having more data.

 

[DIYrich]

If anyone has input on these generator questions, I'd appreciate having more data.

Diesel generator can be the best. I believe they can run on home heating oil. If you expect regular use, this would be the most reliable option.

Keep your propane tank filled. Don't wait for the emergency. Depending on the size, I think 15# is good for 4 hours.

Dual fuel (gasoline or propane) portable generators are available.

If you have batteries, you don't need a large generator. If you use 30kWh per day, a 5 kW generator can run for 8 hours to produce enough power for a day. You can run it manually.

BTW: if you have "rolling outtage", the batteries may be able to recharge from the grid when power is available. 5 hours is a leisurely charge (from empty). 2 hours is ok.

If you have a Toyota hybrid, there are kits to use the car to recharge the battery.

Start with 2 days of batteries. You can always add more to reduce generator hassle.

 

[kommando]

I believe they can run on home heating oil

Depends on the fuel pump on the engine and its requirements for lubrication, kerosene type home heating oil has a lower oil content than Diesel. Older mechanical fuel pumps can take just about anything but modern fuel pumps can need a certain level of oil content depending on the type of pump.

 

[DIYrich]

Depends on the fuel pump on the engine and its requirements for lubrication, kerosene type home heating oil has a lower oil content than Diesel. Older mechanical fuel pumps can take just about anything but modern fuel pumps can need a certain level of oil content depending on the type of pump.

I guess farm diesel to avoid the road taxes.

 

[kommando]

I guess farm diesel to avoid the road taxes.

In the UK they are the same price and oil fired boilers can be adjusted to burn diesel so a common tank can be used but there are some bureaucratic hoops recently added to reduce the usage of farm diesel ie a building site digger moving on the public roads between sites.

 

[Madcodger]

I've heard that generators can run on diesel, but those might be only the smaller-duty generators? Nobody I've talked to about large 15 and 20 kW generators has mentioned diesel, but I'm not sure if it's because they are swayed by manufacture preference. Does anyone know?

This may not apply if you're in CA, but in our area, ALL larger generators are diesel (e.g., local hospital). The people who do residential generators will favor natural gas and propane and may not do diesel at all, but those who do commercial will often be dealing with diesel. I hear you about propane availability. At our place here in Maine (on an island, 1.7 miles from the nearest pavement) we have two 500 gallon tanks, so always have 500-800 gallons available. But that can provide power and heat for a solid month if needed (and if the sun comes out, you might not need to run the generator). Which reminds me - Make sure your generator is rated to run for an extended period. Many are now designed for only 1-3 days of outage every year or two. We also get 5-7 days of no grid power at a stretch and it can go longer in a really big storm, so generators designed for the 'burbs are toys, to us.

 

[Madcodger]

I guess farm diesel to avoid the road taxes.

Yup. In the US, diesel sold for vehicles has a much higher tax added to it, to help pay for roads. "Off road" diesel, or "farm" diesel is generally the same product but has a coloring agent added to it so that if an inspector sees it in a a road vehicle (tractor trailer, delivery truck, etc.,) BIG fines result. Just make sure the off road fuel has anti-gel added to it for winter. There is also some controversy about whether and how long it takes for diesel to oxidize (go bad). Old timers will sometimes say it doesn't, but that's not correct. For me, it's the reason I've gone with propane instead of diesel for our generator. Propane doesn't oxidize to my knowledge, so can be stored for years. I don't have that level of confidence for even treated diesel. It'd be a separate tank from what I use for the tractor, so I don't want to store it for more than about a year.

 

[OffGridForGood]

For me, it's the reason I've gone with propane instead of diesel for our generator. Propane doesn't oxidize to my knowledge, so can be stored for years.

And you can't really "Spill" propane.
Diesel on the other hand, can leak or spill and create an expensive soil clean up job to deal with it.

 

[hwy17]

I think the OP should DIY the design and installation with our help.
After all, they did a mobile system already, just need to take the plunge. We will help.

Santa Cruz County building department is actively hostile to DIY solar and battery permits, so OP would need to decide if he's going permitted or unpermitted first.

 

[OffGridForGood]

Santa Cruz County building department is actively hostile to DIY solar and battery permits, so OP would need to decide if he's going permitted or unpermitted first.

Can they build a mobile unit, and add a "generator plug" with MTS to the house? - have the plug/MTS done my lic electrician, then build a moblie (on wheels even) DIY system ?

 

[hwy17]

Your options from legit installers here are basically Tesla or Enphase batteries. And then the generator backup options will all be bad, big standby generators like you've been quoted for already.

I bought my XW from a north bay solar company that had extensive history with speciality off grid hardware and they said they've gone all powerwalls now. The powerwalls are just too cheap for the high end specialty (simpliphi, Discover, etc.) to compete and they're not going to mess with the lower end hardware, too much time to learn it and too many callbacks. The whole system is set up to check boxes on forms for Tesla and Enphase standard designs now. Wiring a CLP is complicated, backfed systems are easy.

 

[hwy17]

Can they build a mobile unit, and add a "generator plug" with MTS to the house? - have the plug/MTS done my lic electrician, then build a moblie (on wheels even) DIY system ?

I mean you can get away with a lot if you're willing to ignore the code, but no just cause it's got wheels on don't make it mobile. Same with living in a fifth wheel or tiny home trailer.

It's only temporary if it's temporary.