To grid or not to grid...

[cgofish]

Hi folks! I'm looking to move to a new home next year and I've posted about the Off-Grid system we were looking to install which is a 6.12KW system. In preparation for that system I've been reading the forums quiet a bit and notice that frequently comments are made in that if there is ANY possible way to grid tie that is the best choice when it comes down the long term dollars spent.

So this has me second guessing my decision to go fully off-grid.... Is there a good method to calculate when it makes sense to go off grid when grid power is available?

Here is my scenario in rough #s:

Cost for the Off-Grid System: $38,000
Tax Credit (ITC) - $11,400
Total Off-grid after ITC: $26,600

Cost to run electric to the home: $22,000

So after the ITC I'm looking at an initial start up cost difference of $4600. Other factors if I go on grid is the utility costs are currently at 29 cents per kWh (about 3-4 times higher than the US average) with a probable increase in 2017 to 36 cents per kWh.

I know I'll have to look at costs down the road to replace batteries (the ones spec's are Lifepo4 with a 10 year warranty) and I'll probably also need to replace my XW-6448 and other components down the road... I'm not expecting 10 years out of the batteries although it would be nice but hopefully by the time they need to be replaced we will continue to see prices drop.

Either way I'm laying out a good amount of cash so that I'm not sitting in the dark which I'm fine with but like with any large purchase you always want to make the best educated decision possible. I probably need a crystal ball but any input / thoughts would be appreciated.

[SunEagle]

I guess one of my questions would be what is the expected daily kWh generation of that off grid system and will that be enough for you to live on?

Based on the input of other people that live off grid, a system can cost between $2500 to $3500/kWh of generation.

I live in Florida. My home is ~ 2200 sq ft, with a pool, 3 1/2 ton AC, well insulated, solar thermal water heating, but everything is electric although most lighting is either LED or compact fluorescent. I live with my wife and grown Daughter and average about 40 kWh a day. An off grid system for me would cost somewhere in the neighborhood of $130,000 so I am not sure what that $38,000 is getting you.

While my electric grid cost is less than $0.12/kWh even if it was double that amount there is no question that off grid would be the wrong choice for me.

[foo1bar]

[QUOTE=cgofish;n336975]

Total Off-grid after ITC: $26,600

Cost to run electric to the home: $22,000

So after the ITC I'm looking at an initial start up cost difference of $4600.

Do you have net metering?
if you have net metering, I'd probably do a grid-tie system.
Or at least run the numbers.
If the system costs you $18k ($12.6k after fed credit) or $9k ($6.3k after fed credit) it'll cost more up-front than an off-grid, but 1> no recurring battery costs and 2> the property is worth more because it has electric power run to it. (probably worth $25k more even though it only costs $22k to run the new service.)

[cgofish]

SunEagle, I'm also currently living in Fl with a similar electrical footprint as you plus an electric hot tub. The system we designed will be enough for us when we move although our overall electrical usage will be significantly cut back compared to how we live today. No AC in the new house, and gas appliances will help quite a bit along with everything else starting new with as much energy efficient appliances and lighting that we can find. Hoping for output of about 18-22 kWh daily with 5-6 sun hours daily. I'll also have a small generator if I need to do any major power tool work.

Other factors I forgot to add into my equation for considering off-grid or at least a good backup system is that although the utility company charges premium rates for electric the reliability is terrible. Most expect to lose power 2-3 times per month sometimes for a 1/2 day but it can also last a couple days. Another factor is the happy wife happy life factor....and when your working under a deadline and can't work without power it adds to the stress of daily life.

[cgofish]

foo1bar, good point about net metering. I'm getting conflicting information on this but something I need to dig into. As I just mentioned in my post to SunEagle I'd probably still want some kind of battery backup just due to the amount of outages they experience. I don't mind running a generator when needed but it would get old listening to it run multiple times per month.

[SunEagle]

foo1bar, good point about net metering. I'm getting conflicting information on this but something I need to dig into. As I just mentioned in my post to SunEagle I'd probably still want some kind of battery backup just due to the amount of outages they experience. I don't mind running a generator when needed but it would get old listening to it run multiple times per month.

I understand the desire to have a solid emergency power source. Too bad your new POCO does not have the reliability as the one you currently have as well as having a much higher rates.

Still the cost of those batteries and the time you will spend keeping them fat dumb and happy is going to cut into your fun time. As far as I know there isn't any battery system that you can just plug in and forget about. You have to keep a very close eye on them or they will go belly up which is a big expense.

I will also be moving to a new homestead (still in FL but in a more remote location) in a year or so and expect the power reliability to be less then it is now. My plan would be to have a whole house generator in place as well as a 6kw grid tie solar pv system. That generator will be in an enclosure to make it as quite as possible so I do not expect too much noise.

Again the decision of on or off grid belongs to you. I would do the research and make a decision that does not burn any bridges in case you change your mind in the future.

[karrak]

As SunEagle has said you really need to have a very good idea what your power requirements will be before you can make an informed decision on this. Can you look at your current usage to give you some idea what your daily use might be.

This article https://www.solarquotes.com.au/battery-storage/ might give you some ideas. The prices in this article are in Australian dollars, multiply by 0.75 to get US dollars. This article was written prior to the Powerwall 2 which has further reduced the costs. See this article http://solarquotes.com.au/blog/powerwall-2-warranty for cost comparisons including the Powerwall 2.

Simon

[SunEagle]

As SunEagle has said you really need to have a very good idea what your power requirements will be before you can make an informed decision on this. Can you look at your current usage to give you some idea what your daily use might be.

This article https://www.solarquotes.com.au/battery-storage/ might give you some ideas. The prices in this article are in Australian dollars, multiply by 0.75 to get US dollars. This article was written prior to the Powerwall 2 which has further reduced the costs. See this article http://solarquotes.com.au/blog/powerwall-2-warranty for cost comparisons including the Powerwall 2.

Simon

I believe the OP is already looking at an off grid system. The batteries are LFP which will be a lot cheaper then what Tesla is pricing theirs.

[Mike90250]

off-grid here, When you say 6.12Kw, is that the PV array size, inverter size, or battery?

First glance at your #'s. Go grid. I had a quote for about $70K for grid, and sometimes wonder if the push-back at the wife (YOU have the IRON on when the sun is not on the panels !!) would not have been worth it, Or getting up to stat the generator in the snow

[karrak]

I believe the OP is already looking at an off grid system. The batteries are LFP which will be a lot cheaper then what Tesla is pricing theirs.

The price of a Powerwall 2 which includes a BMS, inverter, interconnection hardware, and safety circuitry all packaged in a nice case is about the same as the bare LFP batteries like Calb and Winston prismatic batteries you might use as part of an offgrid system.

Simon

[extrafu]

The price of a Powerwall 2 which includes a BMS, inverter, interconnection hardware, and safety circuitry all packaged in a nice case is about the same as the bare LFP batteries like Calb and Winston prismatic batteries you might use as part of an offgrid system.

Simon

Except that when I called a reseller in Canada (Toronto), he told me that the Powerwall 2 can't be used for off-grid - it must be used in a grid-tied configuration. I think he was fairly clueless but if it's the case or at least resellers think it is, the Powerwall 2 is no option for off-grid usage.

[karrak]

Except that when I called a reseller in Canada (Toronto), he told me that the Powerwall 2 can't be used for off-grid - it must be used in a grid-tied configuration. I think he was fairly clueless but if it's the case or at least resellers think it is, the Powerwall 2 is no option for off-grid usage.

This is all a bit of a can of worms. Depends what is meant as "off-grid usage". As far as I can see the Powerwall 2 cannot be run autonomously, which is a real pain. Still has to coupled up with an inverter that will control the flow of power. Again, as far as I can see the the SolarEdge and Fronius inverters that can be used with the Powerwall 1 can operate in island/backup mode when the grid goes down. I can't see why you couldn't use the backup mode as an offgrid mode. Only problem with this is there is no easy way of charging the battery via a generator. Might be possible to connect a generator to the grid input and use this to charge the battery.

Even if the Powerwall 2 is not as suitable as other batteries for off grid use hopefully the price drop will force the other suppliers to lower their prices.

I am not a great fan of the Powerwall or any other system that makes it hard to hook up other equipment besides what they specify but for people who want a turnkey system with no maintenance and hopefully no hassles something like the Powerwall is probably the way to go.

Simon

[foo1bar]

I don't mind running a generator when needed but it would get old listening to it run multiple times per month.

From what I understand the Honda eu2000i are very quiet. But you pay more for that.
And if this is a new house, just make plans in advance to have the generator(s) on the other side of a shed/garage/whatever, well away from the living room or bedrooms. Downside will be having to walk through the snow to get to them when you need them, but may be worth it. As you increase the distance the sound should decrease by the square (so 2x distance == 1/4 the noise.) Of course other factors come into play- like sound reflecting off things (things in between, off things in back of the generator, off the ground, etc) as well as human perception of sound volume.

[Mike90250]

The powerwall 2 is still vaporware, and cannot be bought. Other things can be obtained, My suggestion is a "starter set" of flooded lead acid batteries to get 2 years down the road, and then see what is on the market to replace them. Powerwall IV ?

[karrak]

Cost for the Off-Grid System: $38,000
Tax Credit (ITC) - $11,400
Total Off-grid after ITC: $26,600

Cost to run electric to the home: $22,000

So after the ITC I'm looking at an initial start up cost difference of $4600. Other factors if I go on grid is the utility costs are currently at 29 cents per kWh (about 3-4 times higher than the US average) with a probable increase in 2017 to 36 cents per kWh.

Which batteries are you thinking of using as part of the $38,000?

To get a good idea of costings using LFP batteries in a system that uses a generator I would look at the system that steveg has put together that cost much less than $38,000. Details of the system are detailed here https://www.solarpaneltalk.com/forum...868#post300868

If it possible to make up an offgrid system similar to the one steveg made using something like a powerwall 2 it should be even cheaper.

If the supply cost and power costs as much as you say I would think there is a good chance it will be cheaper to be offgrid.

Simon