New Off Grid System YOU design!

Rngr275 · May 2012

1st Great site you have here!! Decided to take a different approach.

I have been reading tons of posts trying to soak up as much information as I can so I can make good choices on designing an off grid system and I have come up with the perfect solution. Get help from experts… like most of you here. Here is the readers digest version of what is going on:
We are in the last steps of purchasing an Amish farm in the Finger Lakes Region of NY. We purchased knowing that we would have/want to either go/install an off grid system, or a grid tied system if we could get the grid to the house. Last pole is ~ ½ mile from the house and on a county maintained road. We had the electric company do an engineering study to determine the cost to get the grid to the house and was given an estimate of between 40-60K leaning more on the higher side. After I cleaned myself I decided that there was no way I was going to spend that kind of money (even if I had it) and then pay an electric bill for electric being delivered on my wires and poles. So that leaves an off grid system.
We are a family of 4 and are looking forward to changing our current lifestyle. We do not want to step back into the Stone Age but we will be cutting out many of “Gadgets”. Here is some data for you. Using many different load calculators I have come up with values that range from 3000wh/day up to 5500wh/day. The higher value is running things like washer, TV, water pump more than usual and microwave on the same day or big energy days. I would like to include some solar capability to take advantage of any Tax breaks. I also would like a couple days of battery reserve in the system. I am leaning towards 48V. I like the AGM batteries but I am worried about trashing them during my learning curve. A generator will be an integral part of the system especially in the winter since our average Kwh/m2/day is~2. I plan on using the generator for heavy use days and to keep the batteries in good shape but would like solar to help out when it can.
How about giving me some example systems/ideas? I have been looking into “Certified” installers as it might be worth the money for their help. Is any of this doable for 20?
One last thing, is it possible to have the generator away from the batteries/inverter/controller/house. BTW I have been looking at Hardy and other suppliers for complete systems… are they OK or should I avoid these places.

I apologize for the length of this post.

McD

t00ls · May 2012

Re: New Off Grid System YOU design!

well one thing I noticed you got wrong, it would be 3000 Wh to 5500 Wh.....but not per day, you would need to produce that every hour to run refrigerator washer lights ......

I produce anywhere from 3000 to 6000 watts per day, my system is only 1140 watts of panels.

for 20k you might be able to put a 2000 watt system - the generator,......the batteries for an off grid system are going to be the most expensive item,

depending on your loads , you may need from 500 Ah to 900 Ah of battery....those arent cheap.

35k-40k would get you close to a 4000 watt system with a small generator, which is about what you would pay to have the grid come in......but why pay an electric bill, right.

good luck with the project

Cariboocoot · May 2012

Re: New Off Grid System YOU design!

Welcome to the forum.

Ah, the Finger Lakes! I know it well.

Now, 5 kW hours per day for $20,000? Is that what you're asking? Not likely, but ... how much will you do yourself?

The first thing anyone will tell you is get a Kill-A-Watt meter and measure some of the actual load usage you plan on. You'll probably see that the calculators, based on manufacturers' supplied data, aren't too accurate.

The second thing anyone will tell you is to get that power consumption down as low as possible, as off-grid power comes at a healthy cost. It may even be worth your while to look at grid connection.

For that kind of kW hours you would definitely be looking at a 48 Volt system. Forget the AGM's unless you need their "no gasses in the house" advantage; their price per Watt hour is high compared to ordinary flooded cells and they aren't as forgiving of mistakes.

In addition to the Watt hours, you'll need to know a maximum Watt load to size the inverter by.

Yes the generator can be distanced from the rest. Mine is about 30 feet away in another shed.

You can get a relative idea of power harvest from the PV Watts program: http://www.nrel.gov/rredc/pvwatts/

Keep in mind you'll be looking at around 2500 to 3000 Watts of panel and about 450 - 500 Amp hours @ 48 Volts of battery at least.

Which lake are you near? Chances are I've been there.

BB. · May 2012

Re: New Off Grid System YOU design!

Always ask questions first. Can save you a bunch of money.

Working backwards... Say you want 5kWH per day (not that much power for a home)--You are looking at a cost for off grid power (capital costs, installation, maintenance of new batteries every ~6-10+ years, and new inverter/charge controller/etc. every 10+ years) of ~$1-$2+ per kWH...

5kWH per day or ~150 kWH per month with an equivalent power bill of ~$150-$300 per month equivalent costs (and you pre-pay it because you installed the power plant at your home).

Say 10 year "break even point", that is $150 per month * 12 months * 10 years = $18,000 (to $36k if high end of power costs) over ten years of power costs (and assuming your solar array lasts ~20-30 years).

Does make the $40-$60k install cost by the utility look expensive... But if you live there for 20+ years, it makes the utility cost look a bit more attractive.

Also, I would check with your real-estate agent and see if having grid power to your property will affect its valuation (i.e., is the property worth $40-$60k more if you ever want to sell it).

And, would more electricity be of help to you? Welding/machine shop/crop processing, etc. which can be power hogs...

For the amount of sun you will get--I picked Syracuse NY for PV Watts and got:

Month    Solar Radiation (kWh/m 2/day)
1      2.77     
2      3.36     
3      4.40     
4      4.98     
5      5.45     
6      5.36     
7      5.66     
8      5.32     
9      4.95     
10      3.79     
11      2.34     
12      2.21     
Year      4.22

That is not a lot of sun... Say you want to run 5.5 kWH per day (or 165 kWH per month) for ~9 months of the year without generator use--That gives us February at 3.36 "Hours of Sun" per day as the "break even" month:

5,500 WH per day * 1/0.52 system efficiency * 1/3.36 hours of sun per day = 3,150 Watts of solar array minimum

If you assume around $10 to $20 a watt cost to install a system (your work vs contract, etc.), then:

3,150 watt * $10/Watt = $31,500 system cost (more or less)

There is a lot of slop in that number--but $30-$40k for such a system is certainly a good enough estimate to ask you -- Is this what you are looking at as being reasonable for your needs/expectations?

-Bill

vtmaps · May 2012

Re: New Off Grid System YOU design!

Rngr275 wrote: »

I have been reading tons of posts trying to soak up as much information as I can
<snip>
I have been looking into “Certified” installers as it might be worth the money for their help. Is any of this doable for 20?

Welcome to the forum. Your first post shows that, indeed, you have done a lot of reading. Three years ago I was in much the same situation. Based on my research I was able to design my own system and select the components. I also realized that there are hundreds of nuances to the installation process, and I did not feel confident that I could get them all correct. Many of them are safety nuances. The NEC code was a bit much for me. I ended up hiring a NABCEP installer. I worked with my installer to keep the costs way down. During the summer and autumn I dug trenches, laid conduit and ran it into the buildings, set a pole (for pole mount array), built battery box, put in ground rods, wired the house and had main breaker box installed near the power center. My installer did the installation in the winter (slow season for him) and seemed happy to have work that did not involve getting on a roof. It went smoothly and I got a good price. If you do what I did, I think you can get the system you want for 20k, certainly after 30% federal tax credits.
--vtMaps

Rngr275 · May 2012

Re: New Off Grid System YOU design!

Thanks for the quick replies.
1st our new house is near Keuka Lake (Wheeler).

I appologize for not being a little clearer in my original post.

The center of my Off-Grid power will be the generator. More than likely some configuation of water cooled diesel.

I want to include some level of solar (not the 3-5Kw described for our max load). Enough to "Help" out the system on those 2.7 sunny days in Febuary.

Batteries to store excess generator power when it is running and any solar energy generated from the panels.

We are on a 10yr plan for the house. I am sure that connecting to the grid would be better for the resale but backing out the cost (50K/10years=~$400 per month) plus what ever I use electric is now up inthe $500+ range. @ $550 per month (guess of course instal and monthly use) we are now at ~65K.

Please correct this train of thought: Genset (6-8Kw diesel) + 4-5Kw battery (say 8, 6v 305Ah batteries). Work very hard to keep our use down in the 2-3Kw on most days, plus inverter. For arguments sake say $15K for everything (assumes AGM batteries Hardy Off-Grid System 2). http://www.hardysolar.com/off-grid/homesteader-off-grid-system-2.html If I need to run the generator for 3-4 hours every couple days (which will be the heavy demand days anyway) we are looking at ~15K in diesel so ~$30 K +- some. Add on some supplemental panels and a charge to "help out when it can for another ??? $K and it still feels like we are ahead of the game except for all the hassel (maintanence, battery replacement inside of the 10yr window, etc.)

There are also neighbor right of way considerations that have to be delt with.
What have I gotten myself into!

Hard to decide and know what is best. The only thing I know for sure is we want some electricity in the house.

I ordered a Kill Watt last night.

icarus · May 2012

Re: New Off Grid System YOU design!

I should say it early, to get it off the table. I would reconsider the grid option. In the grand scheme of things, $40-60k is real money, but over the live of the house (and for future resale) it might be quite the bargain. Assuming $50k, amortized over 30 years is $~1700 per year. Consider that a whole house battery bank might easily be $10k with a life cycle of ten years, giving you a simple battery cost of $1000 annually. Add in inverter replacement, genny fuel, battery maintenance costs, and the grid starts to look reasonable.

Consider talking to the utility again. For example, is it possible that you can do (or contract to do) some of the work privately, like setting poles or ditching? Can you get rebated if someone else connects to your main in some time in the future? While I am all for conservation, and indeed for PV, one must realize the great resource that the grid provides. Those of us that are off grid would grid connect in a heart beat if we could. It is important to realize tht off grid power comes at about 10 times the kwh price of grid power, so the advantages of the grid become better as time passes.

Welcome to the forum, there are some very sharp folks here who have forgotten more about PV than most of us will every know,

Tony

vtmaps · May 2012

Re: New Off Grid System YOU design!

Rngr275 wrote: »

The center of my Off-Grid power will be the generator.
<snip>
I want to include some level of solar (not the 3-5Kw described for our max load). Enough to "Help" out the system on those 2.7 sunny days in Febuary.
<snip>
If I need to run the generator for 3-4 hours every couple days (which will be the heavy demand days anyway) we are looking at ~15K in diesel so ~$30 K +- some. Add on some supplemental panels and a charge to "help out when it can for another ??? $K

Make sure you commission the solar panels at the same time as the inverter, epanel, wiring, & batteries. If you add the panels later you will only get the federal tax credits on the panels.

Rather than run the generator 3-4 hours every couple of days, it might be better to run it 1-2 hours daily in the AM and let the panels take over for absorb and float. You will need to run your laundry & other heavy loads while the generator is running.

Buy more panels. They've never been cheaper, and likely won't get cheaper in the future. Diesel is expensive. As far as the Hardy system is concerned, you are spending quite a bit on the generator (although it is a good generator). There are lots of places to buy a prewired Magnum Epanel (including NAWS). For the cost of that generator you could buy a smaller (3-6 kw) Honda inverter generator and enough panels to almost not need the generator. The inverter type generators are real fuel savers, they can run at low speed when the loads are light. Diesel generators do not like to run at low capacity.

When you have a large array, you can get useful power even on a cloudy day.

One more thing... I am happy with my pole mount array. I do regret that I didn't buy a pole mount that allows full vertical orientation in the winter. Vertical orientation sheds snow well. The vertical orientation is steeper than optimal for direct sun, but sun reflecting off ground snow makes up for it.

--vtMaps

BTW, what's the difference (other than $3200) between these systems?
http://www.hardysolar.com/off-grid/homesteader-off-grid-system-2.html
http://hardysolar.com/off-grid/off-grid-energy-system-4kw.html

Eric L · May 2012

Re: New Off Grid System YOU design!

Some of the off-grid price estimates above are a lot higher than what I've found doing it myself, perhaps they are based on older panel price averages or assume high professional installation costs.

I have a running per-watt cost of my current 4.1KW pv system, and while I don't have the figure with me now, it's under $3/watt. To be sure, I did all design and installation myself, and DIY-ed whatever I could (panel mounts, principally). I also got great prices on panels (.78/watt) and on batteries locally. This system has no problem delivering a reliable 5KWh/day.

With $30K I think could make one king-heck of an off-grid pv system, lol.

stephendv · May 2012

Re: New Off Grid System YOU design!

icarus wrote: »

Consider that a whole house battery bank might easily be $10k with a life cycle of ten years, giving you a simple battery cost of $1000 annually.

That seems a bit steep. NAWS sells Crown deep cycle industrial battery which are supposed to last over 20 years and only cost a little over $5000 for 500Ah @ 48V.

Based on what others have commented, a 3kW array and 530Ah 48V battery seems about the right ballpark. System price would look something like:

2 x 24V 530Ah Forklift batts:
http://www.solar-electric.com/crinba24vo53.html = $5600
Charge controller: http://www.solar-electric.com/mnclassic.html = $600
4kW inverter: http://www.solar-electric.com/maenms4444wa.html = $2200
3kW of panels: http://www.solar-electric.com/kykd235wamus1.html = $4800

= $13,200 without the generator.

About generators. The type of generator you need will depend on how often its used. The perkins you linked to is the most solid, reliable unit meant for 24/7 operation. It is also the most expensive option, but should give you many years of trouble free service. So if you sized the solar panels in such a way that you would need the generator every second day or so from November to March- then it's probably a good choice.

But if you installed more panels then you won't need the generator that often- and then you don't need an industrial quality generator and could get by with a smaller and cheaper gasoline or propane version. A portable gas version would also be very useful to have around the farm.
I think you'd need accurate weather data for that area to know how much more PV you would need to make the step down to a smaller gen.
...and no ongoing costs for PV

Cariboocoot · May 2012

Re: New Off Grid System YOU design!

Well that's a different way of doing it; diesel first. Fuel must be cheap in NY.

There's a problem with using a few solar panels to help with charging when the sun shines (2.7 days in Feb? Never had that much in Geneseo!) That is a few panels won't actually do much for charging.

If you're looking at 305 Amp hours @ 48 Volts you'd have about 6 kW hours AC power from that (50% DOD). You'd also have a battery bank that could be recharged with an 1870 Watt array on most days. That would save a lot of diesel. Would it save the $5,000 the array would cost? Over time certainly. It ought to last 20 years so that's less than $300 a year for 600 to 700 kW hours (roughly speaking), or $0.50 per kW hour (array cost, guys; not whole system). It won't need as much maintenance as the gen either. Nor make as much noise. None, in fact.

BTW, I calculated that on the array output like this:
1870 Watts * 4 hours equivalent good sun * 50% over-all system efficiency = 3.740 kW hours AC per day * 183 days (half a year; I know NY

) = 684 kW hours per year. Panels @ $3 per Watt = $5,610 / 20 years = $280.50 per year / 684 kW hours = $0.41 per kW hour. And that is conservative, right?

I agree with Stephen; go for the panels and save on the diesel. A 3 kW array should provide 6 kW hours per day AC on good days and work well with 530 Amp hours of 48 Volt battery. A 4kW inverter will run most anything you've got, unless you turn it all on at once, and a 3 kW gen could recharge it when needed (if you're careful with loads - 6 kW if you're not).

In case you haven't guessed, load management is a big part of off-grid living.

P.S.: My brother used to live in Prattsburg, so I have stomped around Keuka and environs.

Photowhit · May 2012

Re: New Off Grid System YOU design!

stephendv wrote: »

= $13,200 without the generator...

...fusing, racking, grounding, wiring, shipping...

There is no reason you can't start reducing now to see what you can live with out, this might well be the hardest with wife and kids. You want to be sure everyone's onboard.

That said I'm putting together a similar system/ w/o the generator backup, I want AC in the summer or I could live with a much smaller system. Design of the complete system is important, in this case, I'd include the house. My guess is it's never been wired? Big expense!!! Electric fridge, gas stove, washer,... I bet there's already a good solar dryer!

I have a 24v system (I'd have gone 48V but had purchased a 24v traction/forklift battery just before finding a deal on a modular home w/2 acres). I have @$5200 invested with careful shopping, another $2600 in the battery (24v 800Ah), and need 2 Charge controlers(@$1300) and racking yet. I'm drilling out some angle for aluminum mounts in the next week. I'll have 30% returned in a tax credit, federal tax credit is good through 2016, rumors of this continuing at 10% after that. I'll do all the work my self, fine in Missouri and my 10 years of off grid experience.

I think it's very 'doable' within your budget, just not sure the house or your family is ready for changes. I lived with a 200watt array and no backup for several years, and 9 months in a tent cycling around before that, so a 4Kw array is luxury for me!

I bicycled through the finger lakes area, very pretty.

Rngr275 · May 2012

Re: New Off Grid System YOU design!

Thank you for your patience.
icarus: Believe me I want to hook to the grid and have looked at it the same way you describe. I am just not sure I can right now as mentioned huge up front cost not including the 1/4 mile long swath ~40ft wide of lumber that will have to come down on my neighbors land... if he will give me a right of way. Very frustrating.

FYI for everyone... this is my wifes dream house and she is the driving force. The kids think it is great but I don't think they full comprehend the extent of the changes that will be required. Though I will attempt to make it as enjoyable as possible. i.e. movie day, or x-box for a couple hours as a reward, things like that.

vtmaps: No clue what the difference is between the 2 systems. I probably won't buy from them but was using their system as a blueprint.

I in know way want to live on or need to run a generator for hours and hours everyday. But I do expect to have to use it to protect the batteries health, and if there is a need for it. i.e. wash day, power tools, X-box day.

And for generators, I am glad to see consensus on needing an 8Kw diesel generator. Portable would be much handier. Is it worth the extra money for the inverter type generators? (Honda,Yamaha,etc) I know that the provide a more pure sine source of AC but is it necessary when feeding the charger in the system, and or other things around the house. I ask because I could buy a 6Kw Generac at Homedepot for less than $700, and then a smaller invertor style generator for 1000-2000 depending on size. Just trying to maximize usability and reduce cost. ~4K for a Honda 6Kw generator.

I like everyones idea of maximizing the panels. I will focus on a 3-4Kw panel set. Is it better to try and piece it all together or do one stop shopping, or let who ever I hire to assist (which I still feel I need) handle the purchasing, with my input. The Pv system will be purchase so that I will be able to take advantage of the Fed. TX credit.

I see those batteries weigh a ton (well not quite) are there other options just to make the moving and handling a little less of a monumental task?

BTW... The house is ~ 5miles from Pratsburg. I am having the house partially wired (circuit box, and some of the rooms) by an electrician and will add rooms and circuits as needed. Great way to reduce usage don't you thing.

Should be a great year for Whine here in the Finger Lakes for my family... if you catch my drift!:D

Cariboocoot · May 2012

Re: New Off Grid System YOU design!

Inverter-generators are great, but in this case probably not the right choice. Their benefits include being very quiet, having really pure AC (no discernible frequency fluctuation), and saving on gas when lightly loaded. In your case you are looking for over 3 kW of power, which is about the upper limit of the I-G type. And you will be loading it when used, so there's no fuel savings to be had from one either.

It's best to buy your panels all at once. Next year the model you bought this year may no longer be made, and then you can be up against the problem of trying to get mis-matched panels to work together.

Batteries weigh a lot. Not much can be done about that. You want to try to keep it to a single string, so the best option is to divide it up into 6 Volt units or even 2 Volt units (pricey). The forklift batteries are great, but they are monolithic monsters and difficult to manage without, aha, a forklift. You'll be better able to decide on batteries once you've got some real world load numbers to work with and can finalize a battery bank size.

You know what's funny? Last time I was in NY I tried to buy some NY wine to bring back with me. Couldn't find any in the stores. I suppose I'd have to go search the wineries! Talk about ironic. :roll:

Photowhit · May 2012

Re: New Off Grid System YOU design!

I think you missed someone's earlier point, in that your solar electric system, is covered in the tax credit, hence if your designing a system with 3Kw of array, a real solar electric system, with generator backup, your battery and wiring all would qualify for the tax credit. I looked into this, easy for me since I don't run any backup at all. While generator and transfer switching I don't think qualify, the battery would (think big bucks...)

There are many doable things in this day, with the kids and wife onboard, it will be a great learning experience. So long as the 'big dog' doesn't rub it in if/when there are problems.

BB. · May 2012

Re: New Off Grid System YOU design!

Regarding Batteries, make you battery location easy to unload and move (concrete floors and staging area outside, no steps, and/or crane/forklift accessibility).

You probably want to keep the battery bank between ~freezing and 80F--Too cold, you loose capacity (and discharged batteries freeze easier)--Too hot, they will have shorter operating life (roughly, every 18F/10C increase over ~77F/25C knocks 1/2 the life off the batteries). Insulated building, 1/2 buried "bunker" etc. can help keep batteries at an even temperature.

Operating/cycling batteries in an insulated box/room probably do not need additional heating during winter.

Keep things separate... You don't want a generator fire to take out your solar array/battery bank/home... Battery bank needs fusing and and emergency off switch--especially if the bank in in the basement/home (follow code the best you can with DC).

-Bill

westbranch · May 2012

Re: New Off Grid System YOU design!

from my experience you want to keep the cells/ batteries at no more than 150 # so that you can manhandle each one on and off a hand cart. More gets so difficult, exponentially so...

hth

Photowhit · May 2012

Re: New Off Grid System YOU design!

westbranch wrote: »

from my experience you want to keep the cells/ batteries at no more than 150 # so that you can manhandle each one on and off a hand cart. More gets so difficult, exponentially so...

What if you didn't have to move them for 20 years? ...says the guy who bought an 1100lb battery last year and will likely move it to his new home....lol. I Like outside storage, I will berm up around the battery at my new location, just incase I decide to let a family try to run off the system.

Rngr275 · May 2012

Re: New Off Grid System YOU design!

Thank you for your replies and insight. This is a living project and changing at every twist and turn.

I have meetinf set up with 2 installers to discuss what they offer and their experience, etc. One happens to live off grid.

Since I am noe definately going to buy a water cooled diesel (thank god) I am looking at a portable that can be moved in and out of the celler to charge the system as needed. Question about sizing: Too small a generator I expect it will have to run longer to charge the batteries than a larger out put generator. How does Kw out put of the gererator related back to the size of your batteyr bank.

The battery bank and all the electronics/electrical stuff will be stored in the cellar (no steps for access) I will make some sort of enclosure for the batteries and vent. The good new is the temperature should be fairly stable in the 45-60 range depending on the season.

I really don't think the 1000+ forklift batteries are the way to go for me. Something a little smaller will have to be made to work.

Question on load calculators. I have ordered a Kill watt to do actual measurements. In the mean time the spreadsheet calculators are very confussing. It asks for you appliances and then calculates your daily wattage needs. But if I put in a washing machine and a TV it assumes that I will use them both on the same day. For instance say the washe uses 500w and I run 3 loads of wash for an hour ea.= 1500w 1 day a week or an average of 215whr/day (not including system loss), I watch TV 2hrs a day 7 days a week @ 150w/hr... that equals 300whr/day ((not including system loss), So the calculator tells me I have 500whr/day for those 2 items but in reality It could be 1800whr (All laundry and tv on 1 day), 215whr if I do laundry and no TV on 3 different days. Or I just run my generator to do laundry, watch TV and top off the batteries on that day, which might optimize the generators use.

I get a little confused at time but this is all new to me.

My numbers keep coming up to 1.5-5.5K of electricity a day according to how I decide to use the "Juice" on any given day.

wrdaigle · May 2012

Re: New Off Grid System YOU design!

You may want to consider replacing some of your heavy hitter appliances. It has been a while since I tested it, but I think our high efficiency washer uses just over 100wh per load and we hang dry out laundry, summer and winter. You can certainly get a big screen lcd TV that runs on less than 100w. We use a converted AC chest freezer as a fridge that uses about 300wh per day. The only real heavy hitter we have is a DC chest freezer (~700wh).
Really think about where your energy use is. A minor change can make a significant difference. You might even be able to get away with a smaller system. The savings will more than pay for any appliance upgrades.

Eric L · May 2012

Re: New Off Grid System YOU design!

Question about sizing: Too small a generator I expect it will have to run longer to charge the batteries than a larger out put generator. How does Kw out put of the gererator related back to the size of your batteyr bank.

One rough sizing guideline is to shoot for around 10% of the amp-hour capacity of the batteries (at the 20-hour rate) in charging amps. So if you have a 500 amp-hour battery bank wired in series for 48 volts, you'd shoot for 50 amps (10% of 500) X 48 volts charging = 2400 watts, but you also have to factor in running loads (items that are running when you charge that the generator must also carry). If that averages another 800 watts (say), then around 3200 watts of generator capacity to recharge, maybe rounding up to 3500 to cover some charging inefficiencies. I don't live off grid and more experienced posters may have better advice, but that's a starting point for you.

Many off-gridders here prefer small, high-efficiency generators over big ones.

The last stages of battery charging are the least efficient: i.e., you get out the lowest percentage of what you put in when you charge. So if, say, you get out 95% of what you put in to the batteries back out when you charge them from 60-80% full, you might only get out 80% of what you put in when you charge them from 90% to 100%. Also, this last 10% (absorption) phase of charging takes the longest. Consequently, I know some posters here do not fully charge the batteries when they need to run the generator, but instead stop 'early' with the gen and rely on their solar pv to fully charge them when the sun returns.

Or I just run my generator to do laundry, watch TV and top off the batteries on that day, which might optimize the generators use.

When possible, you're going to want to do some things like laundry when it's sunny, after the batteries have charged up and you have 'surplus' electricity from the pv panels. Personally, I would not factor intermittent like the washer into my regular loads (UNLESS your household needs to do laundry almost every day), but see it as an 'opportunity' load for sunny days. However, make sure the inverter and other equipment can handle a washing machine, which a larger pure-sine-wave inverter will.

Do you know what kind of winter cloud conditions you're looking at there? I think one of your biggest design considerations is going to be what happens when you get, say, 5 or 10 consecutive days of overcast (guessing this might happen, e.g., with lake-effect weather). Your pv will only put out maybe 10% of its normal output during these conditions, so this is when your gen might have to run a lot.

Cariboocoot · May 2012

Re: New Off Grid System YOU design!

Rngr275 wrote: »

Question on load calculators. I have ordered a Kill watt to do actual measurements. In the mean time the spreadsheet calculators are very confussing. It asks for you appliances and then calculates your daily wattage needs. But if I put in a washing machine and a TV it assumes that I will use them both on the same day. For instance say the washe uses 500w and I run 3 loads of wash for an hour ea.= 1500w 1 day a week or an average of 215whr/day (not including system loss), I watch TV 2hrs a day 7 days a week @ 150w/hr... that equals 300whr/day ((not including system loss), So the calculator tells me I have 500whr/day for those 2 items but in reality It could be 1800whr (All laundry and tv on 1 day), 215whr if I do laundry and no TV on 3 different days. Or I just run my generator to do laundry, watch TV and top off the batteries on that day, which might optimize the generators use.

I get a little confused at time but this is all new to me.

My numbers keep coming up to 1.5-5.5K of electricity a day according to how I decide to use the "Juice" on any given day.

Did I mention load management? Here's where it really shows up! Also why the "calculators" aren't as useful as they might seem.

What you shoot for is your average daily Watt hours. Since you only run the washing machine occasionally, that can be deemed an extra load to be run from the generator only. Other loads, like water pump, can be controlled to only come on when the batteries are full and the sun is still shining. It takes a bit of juggling and practice as well as planning. You have a generator in case you get it wrong and need to recharge ASAP or at night. It is definitely a change in lifestyle.

Eric, despite not living off-grid, has got it right about the generator sizing: charge rate @ Voltage = Wattage, apply the power factor of the charger, add the loads, round up. As I said before in your case the larger conventional generator may be the better choice, but you won't know for certain until you get the loads finalized and the rest of the system designed.

I'll add the info that if you buy an inverter-generator like the Honda EU2000i you can get two and run one when that's all you need or connect them together if more power is required. A bit silly, really, but it could be done.

I hate to say it but once you actually start living off-grid you're going to see what you did wrong. There's no way to predict it in advance, because everyone's site and usage is different. But it is inevitable that you will say "I need a bigger/smaller generator/battery bank/array/inverter/bank account". Well no; the bank account always needs to be bigger.

westbranch · May 2012

Re: New Off Grid System YOU design!

A quick add about generators and chargers. The biggest draw will be at the moment you connect the power to the charger, it can last for 10's of minutes, or longer depending on DoD, and this is the point of need for a 'larger than needed' for most of the charge cycle. There are ways around it if you are willing to 'play' a bit. But they will require your close attention.

Rngr275 · May 2012

Re: New Off Grid System YOU design!

westbranch wrote: »

A quick add about generators and chargers. The biggest draw will be at the moment you connect the power to the charger, it can last for 10's of minutes, or longer depending on DoD, and this is the point of need for a 'larger than needed' for most of the charge cycle. There are ways around it if you are willing to 'play' a bit. But they will require your close attention.

Westbranch... So you are saying that it is better to have an oversized generator than an undersized?

New Off Grid System YOU design!

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