Solar Backup vs Backup Generator

[jwbarrios]

Hey guys, I need some help sorting through some thoughts. I am in the Dallas, tx area. First, my long term goal is to eventually be grid-tied with Solar. I am currently paying 9.1¢ per kWh* and using about 1200/kWH per month. I need to do this in spirts, due to the upfront cost but want something I can eventually expand easily. Initially, I would like to have a 1 or more days backup in case of power outages (assuming I can charge them fast enough in the day. I am not looking to power the entire home, just a few items (AC or gas heat pump), kitchen fridge, (1) 65-inch tv, internet, 2 laptops a lamp or 2, Microwave and charge the cell phones. (lets assume, everything will run for 5-6 hours a day)

Now with that background info, I travel on and off for work and want it to be fairly easy for my wife to operate, should I be on the road.

I could get a gas/propane generator (not an entire home system, but the smaller system?), install a manual transfer switch and wire the room that has basically all the items. Pro/con - cheapest solution, can get that done in 1 day, no extension cords etc. Con, noise, fuel storage (looks to be about ~2500.00) all in

Install the full gas auto-transfer system (looks to be about 7-10k all in) - Pro/Con - expensive, but easy.. Takes me away from my solar goals

Go with a Small solar grid-tie system - this is where i get stuck - maybe 4-6 panels, batteries, BMS, inverter, it seems like it needs to be grid-tied or have a transfer switch. (cost~4k? )

any thoughts

 

[onemorebattery]

At $.091/KWH you're not going to save money running a generator and your cost recovery on solar is going to be many years so backup power during outages is probably all you really stand to gain.

You'd need a 7KW array or 7KW generator producing for 6 hours to make a day's worth (40KWH) of juice. Powering a partial home is doable. Enough solar gear to run your AC for $4K is a tall order.

I'm a huge solar advocate but if I'm hearing you right my best advice is get a hefty generator with automatic transfer switching to cover the power outages. Do a home energy audit (see if you can knock back that 1200 kWH per month) to get a better idea of the solar package you would need to power your essentials.

 

[Ely]

Only solar. A gas generator bringing expensive costs, fumes, maintenance and so on. Configure a solar system and it runs many years without any maintenance. In Dallas, TX, you have a lot of sun to recharge the batteries quickly.

You really need 1200 kWh per month? Holy cow, it's extreme. This are about 40 kWh a day. We take about 4 kWh per day, only 10%

All heating or cooling pulls extreme energy. So an air condition takes a lot of energy and it's not recommended to run an AC with battery power. And generally not recommended to run such things offgrid.

 

[Knighthawk]

IMO, get you a charge controller that can handle a ton of panels now. Or an all in one system that can handle all your needs now. Then slowly add panels and batteries. I would keep a small generator on hand just to charge the batteries if bad weather strikes for multiple days.

 

[svetz]

... grid-tied ... want something I can eventually expand easily.

Microinverters (e.g., Enphase) are the undisputed king for getting in cheap and being able to expand easily. Basically it's one microinverter per panel, so you can expand one panel at a time if you like. If you right-size your wires off the roof on the initial install for what you think your max installation will be, you'll never have to fork-lift replace anything. Many people hire a professional installer to install a very small system, usually for under $3/W. This is nice as they take care of all of the up-front stuff (e.g., permits). It also lets them DIY add on panels later. Just make sure they know that's your plan so they can properly scale the wire/breakers on the initial install. No worries about mixing/matching/sizing anything!

...I would like to have a 1 or more days backup in case of power outages...

Batteries are expensive. That's like saying abandon all hope ye who enter here.
3 Days of power is three times more expensive. For eample, Enphase has a 3kW battery for $4000.

Having a generator is much cheaper. Having a natural gas generator is even better (no trying to find gasoline).

If you do DIY a battery, You might be able to get the costs down to < $650/ kWh for Lithium.

You could still use Enphase, but they'd need an AC coupling solution which adds to the costs. Not going Enphase means you need a string inverter which are sold in units of power they can handle. These can be expanded if they have the parallel feature. It's more complicated and takes a lot more planning this route.

As it's for emergency use, lead acid batteries have a pretty good use case. See the Battery FAQ, and look into PCCs. Lead Acid batteries take up a lot of space and are very heavy.

... I am not looking to power the entire home, just a few items (AC or gas heat pump), kitchen fridge, (1) 65-inch tv, internet, 2 laptops a lamp or 2, Microwave and charge the cell phones. (lets assume, everything will run for 5-6 hours a day)

You'd want to build a power budget. List each item, how many watts it uses per hour, and how many hours per day you use it for. You can get watt meters to help with that.

...Go with a Small solar grid-tie system - this is where i get stuck - maybe 4-6 panels, batteries, BMS, inverter, it seems like it needs to be grid-tied or have a transfer switch. (cost~4k? )

Sounds like you want to start with a 2 kW system. Here's a pretty good list of hybrid string systems. Look for one that can be paralleled and meets your needs. Let us know what you're thinking beyond that and hopefully you can get some tips and tricks that will help you out. Good luck!

P.S. Posting the same thing in multiple threads is considered spam... please don't do that.

 

[WildLeg]

Just posted this DIY Grid TIED 2kW system with future Ensemble.

Owner-Builder DIY, Enphase, Iron Ridge, Florida

1) Anyone interested in installing their own GRID-TIED Solar Photovoltaic system but are put off by the permitting process...it's not as difficult as you may think. I have recently completed a permit packet for Southwestern Florida where "owner-builder permitting" is allowed. If you are...

diysolarforum.com

 

[WildLeg]

Looks like Texas also allows owner-builder permitting.

https://dallascityhall.com/departments/sustainabledevelopment/buildinginspection/DCH%20documents/pdf/BI_Homeowner%27s%20Exemption%20from%20Registration%20as%20a%20Contractor.pdf

 

[jwbarrios]

At $.091/KWH you're not going to save money running a generator and your cost recovery on solar is going to be many years so backup power during outages is probably all you really stand to gain.

You'd need a 7KW array or 7KW generator producing for 6 hours to make a day's worth (40KWH) of juice. Powering a partial home is doable. Enough solar gear to run your AC for $4K is a tall order.

I'm a huge solar advocate but if I'm hearing you right my best advice is get a hefty generator with automatic transfer switching to cover the power outages. Do a home energy audit (see if you can knock back that 1200 kWH per month) to get a better idea of the solar package you would need to power your essentials.

I am looking to do a power audit in the near future before I buy anything. We have ~3kSQft home and that has 3 AC units and have been all home every day for the last ~3 months since we just had a newborn and then this whole corona thing. Specifically, I think I am just looking (in the event of a power failure, so I expect the daily needs would dwindle down if the power went out for a few days. At that point, it would be basics only.

 

[jwbarrios]

Only solar. A gas generator bringing expensive costs, fumes, maintenance and so on. Configure a solar system and it runs many years without any maintenance. In Dallas, TX, you have a lot of sun to recharge the batteries quickly.

You really need 1200 kWh per month? Holy cow, it's extreme. This are about 40 kWh a day. We take about 4 kWh per day, only 10%

All heating or cooling pulls extreme energy. So an air condition takes a lot of energy and it's not recommended to run an AC with battery power. And generally not recommended to run such things offgrid.

interesting.... No AC in the summer in Texas can get pretty rough, especially with an Infant I would imagine. I could run only one AC

 

[jwbarrios]

IMO, get you a charge controller that can handle a ton of panels now. Or an all in one system that can handle all your needs now. Then slowly add panels and batteries. I would keep a small generator on hand just to charge the batteries if bad weather strikes for multiple days.

Knight, do you have an example of that controller? I would hate to have to go back and buy another controller later on. I looked at home systems and trying to do the math (with the tax breaks to see if its doable this year)

 

[jwbarrios]

Microinverters (e.g., Enphase) are the undisputed king for getting in cheap and being able to expand easily. Basically it's one microinverter per panel, so you can expand one panel at a time if you like. If you right-size your wires off the roof on the initial install for what you think your max installation will be, you'll never have to fork-lift replace anything. Many people hire a professional installer to install a very small system, usually for under $3/W. This is nice as they take care of all of the up-front stuff (e.g., permits). It also lets them DIY add on panels later. Just make sure they know that's your plan so they can properly scale the wire/breakers on the initial install. No worries about mixing/matching/sizing anything!


Batteries are expensive. That's like saying abandon all hope ye who enter here.
3 Days of power is three times more expensive. For eample, Enphase has a 3kW battery for $4000.

Having a generator is much cheaper. Having a natural gas generator is even better (no trying to find gasoline).

If you do DIY a battery, You might be able to get the costs down to < $650/ kWh for Lithium.

You could still use Enphase, but they'd need an AC coupling solution which adds to the costs. Not going Enphase means you need a string inverter which are sold in units of power they can handle. These can be expanded if they have the parallel feature. It's more complicated and takes a lot more planning this route.

As it's for emergency use, lead acid batteries have a pretty good use case. See the Battery FAQ, and look into PCCs. Lead Acid batteries take up a lot of space and are very heavy.


You'd want to build a power budget. List each item, how many watts it uses per hour, and how many hours per day you use it for. You can get watt meters to help with that.


Sounds like you want to start with a 2 kW system. Here's a pretty good list of hybrid string systems. Look for one that can be paralleled and meets your needs. Let us know what you're thinking beyond that and hopefully you can get some tips and tricks that will help you out. Good luck!

P.S. Posting the same thing in multiple threads is considered spam... please don't do that.

Microinverters (e.g., Enphase) are the undisputed king for getting in cheap and being able to expand easily. Basically it's one microinverter per panel, so you can expand one panel at a time if you like. If you right-size your wires off the roof on the initial install for what you think your max installation will be, you'll never have to fork-lift replace anything. Many people hire a professional installer to install a very small system, usually for under $3/W. This is nice as they take care of all of the up-front stuff (e.g., permits). It also lets them DIY add on panels later. Just make sure they know that's your plan so they can properly scale the wire/breakers on the initial install. No worries about mixing/matching/sizing anything!


Batteries are expensive. That's like saying abandon all hope ye who enter here.
3 Days of power is three times more expensive. For eample, Enphase has a 3kW battery for $4000.

Having a generator is much cheaper. Having a natural gas generator is even better (no trying to find gasoline).

If you do DIY a battery, You might be able to get the costs down to < $650/ kWh for Lithium.

You could still use Enphase, but they'd need an AC coupling solution which adds to the costs. Not going Enphase means you need a string inverter which are sold in units of power they can handle. These can be expanded if they have the parallel feature. It's more complicated and takes a lot more planning this route.

As it's for emergency use, lead acid batteries have a pretty good use case. See the Battery FAQ, and look into PCCs. Lead Acid batteries take up a lot of space and are very heavy.


You'd want to build a power budget. List each item, how many watts it uses per hour, and how many hours per day you use it for. You can get watt meters to help with that.


Sounds like you want to start with a 2 kW system. Here's a pretty good list of hybrid string systems. Look for one that can be paralleled and meets your needs. Let us know what you're thinking beyond that and hopefully you can get some tips and tricks that will help you out. Good luck!

P.S. Posting the same thing in multiple threads is considered spam... please don't do that.

svetz, this makes sense.
1. Do the power audit.
2. Determine the optimized full load system might look like (long term)
3. Determine what the Short term grid-tie system might look like 2kW system during the day, will have some power to the home to power on a few things, but at night, nada.. So maybe look at the battery system upfront.
4. Determine what the backup power "need is" what is critical to comfort and nothing else. So just enough battery to get through the night (look into different battery storage systems)
5. Or Get a small dual fuel generator to run the critical items at night/
6. Get Enphase or whomever to do most of the design and permits and get them to build out the locations for future panels, run all the wire, etc. From there,I would just buy panels as I go or add the battery pack later on but all the cabling and such would be done upfront

 

[jwbarrios]

Just posted this DIY Grid TIED 2kW system with future Ensemble.

Owner-Builder DIY, Enphase, Iron Ridge, Florida

1) Anyone interested in installing their own GRID-TIED Solar Photovoltaic system but are put off by the permitting process...it's not as difficult as you may think. I have recently completed a permit packet for Southwestern Florida where "owner-builder permitting" is allowed. If you are...

diysolarforum.com

Wildleg, that is just about what I am thinking about doing based on me reading all the posts in the thread !

 

[jwbarrios]

Got a quote from Green mountain installer (the power company i use) they have a credit program for installing Solar and then the Fed tax incentive.. Any thoughts on that?

 

[erik.calco]

I implemented this and am very happy with it. This is a starter. I can scale. But, no matter what, I start with 10 circuits to choose from at any given time for "critical load". If power goes out, whatever is on critical load will keep running.

Note that I ran this for awhile without PV waiting for winter to pass. It works great as a UPS even with AC charging. But, I've begun adding strings to PV, so am doing a lot less AC charging.

But, the beauty is it will direct utility to load, so I'm not necessarily using up my batteries with my load, even without sun.

As for scalability, I can add up to 3 of these inverters for a total of 4, and they will connect to each other and work together. With two, you can have 2 phase if you need it.

I got a $40 laptop via craigslist I dedicated to it, and use VNC to remote into it. So, i can monitor, configure and tweak it at any time using the free software available for it.

I thought of you because you want to start out small, and be able to scale, while still using utility. That was exactly my thought when I designed this. The only difference is I have zero plan to grid-tie (feed the grid). This setup may convince you that you don't need to. Technically, this is an off-grid setup. But it is very much designed to slowly ween you off utility power with solar while providing backup when utility is down.

 

[jwbarrios]

IMO, get you a charge controller that can handle a ton of panels now. Or an all in one system that can handle all your needs now. Then slowly add panels and batteries. I would keep a small generator on hand just to charge the batteries if bad weather strikes for multiple days.

what are your thoughts on the SolArk inverters?

 

[madmax]

9c a kw... Delivered?
I pay 24c delivered. Delivery cost per kw is pretty much the same as the kw cost here, which makes hybrid loads (or shared loads) more pallatable.

Trying to do only solar as a backup will be costly, as their peak kw output is so expensive compared to a generator. Their general usage is different as well, generator only operating when the grid is down.

I did something similar to Erik. Though my battery is way smaller. The mpp does support dry contact gen set starting. But you would need an auto transfer switch to sense a switch over from grid charging to genset power, just like a hard setup genset.

You can however run a tiny inverter gen, and still run a lot. The inverter and battery handle peak loads, while the tiny generator keeps topping off the batteries.