600kwh a month

fauss

I use 550 to 600kwh a month. 20kwh a day. How do I size my system from that? I'm starting small just to get the feel for solar and only going to power a small wood shed till I can afford a grid tie system with battery back up. Which is not going to be any time soon cause that's a lot of doe I have to save. Just ordered 2 x 100w renogy panels with a 40 amp mppt. I'm wondering about an inverter. Do I buy one to meet my needs in a year from now? For now I want to run some DC lights and be able to charge some small devices and other rechargeable batteries I have with hopefully an inexpensive inverter. Also by the time I integrate solar in to my house I will have cut down my consumption with led lights and maybe a different fridge. Sorry it's one long rambling question. Thanks and any feedback is appreciated.

fauss

Also what about fuses. Am I going to need them on a 200 watt system

Johann

fauss
A cheap DC to AC inverter may not be of your interest since they are mostly MSW (modified sine wave inverters). Electronic equipment and motors do not like them and may burn up. Those inverters usallly use more standby power and may use more power to turn DC into AC. MSW inverters are also known to burn up cordless tool battery chargers.
Those cheap grid-tie-inverters from china are most likely illegal to use with your power company. Power companies may require a UL  listed grid-tie-inverter and may have to sign off before you can hook it up and use it.

Photowhit

What are your terminal goals?

Do you plan to save money in the long run?

Do you need the an uninterrupted power supply?

Where do you live?

You won't need fuses or breakers between the panels and the charge controller. You will likely want a breaker or fuse between the battery and inverter. It's nice to have breakers between each device to use as shut offs. Some battery chargers have issues with modified sine wave inverters. I checked and the model Dewalt battery charger introduced in 2000 works fine from a modified sine wave inverter, the previous versions did not. I think there was one more modification to the Dewalt chargers for the pod type NiCD batteries.

We don't know your ambitions for loads in a year, if you need a pure sine wave inverter, I would at least look at what your loads will be in a year.

Please note, the panels you purchased will NOT integrate well into a grid tied system, also the batteries and charge controller will NOT. so you are spending money for this system to experiment and learn, but the money will likely be a waste toward your future system.

Also battery backed hybrid systems, will not save you money. They can be useful if you need a backup for medical reasons. The net total you may spend on electric could be much more than you are spending currently.

fauss

I do plan on getting a pure sine wave inverter when I decide to tie in to the grid. And I would do it legally with an inverter that was meant for it. But while I save up enough money for panels and the right inverter I just want a small off grid system with 3 led lights on for an hour a night, a radio on for a couple hours a day and be able to charge things with a USB.

Still completely new to all this so forgive me but what's wrong with 100w 12v panels? Do you have to have 250w panels to have a grid tie? And about the charge controller I know 40 amp charge controller won't be enough for my whole house but can't I use 2 or 3 together to share the load?

I live in the Pacific Northwest so sun conditions are not ideal. I have a wood stove for heat. GE refrigerator built in 2001 that I'm currently trying to find out the wattage it uses when it surges. I never use my microwave. A dishwasher that i rarely use. Also it's not hot enough here to hang dry clothes so I have to be connected to the grid for my 220w clothes dryer. Really in the near future I think I just want solar to help with my electric bill. And I lose power every winter do to fallen trees. ( I have a generator too)

And yes I'd like to save money by buying quality stuff once rather than constantly upgrading.

This site has a ton of info and I'm learning a lot. Thanks again

oil pan 4

How about start by not using so much power. It's cheaper to save power than to generate it.

Photowhit

fauss said:

I do plan on getting a pure sine wave inverter when I decide to tie in to the grid. And I would do it legally with an inverter that was meant for it. But while I save up enough money for panels and the right inverter I just want a small off grid system with 3 led lights on for an hour a night, a radio on for a couple hours a day and be able to charge things with a USB.

Still completely new to all this so forgive me but what's wrong with 100w 12v panels? Do you have to have 250w panels to have a grid tie? And about the charge controller I know 40 amp charge controller won't be enough for my whole house but can't I use 2 or 3 together to share the load?

I live in the Pacific Northwest so sun conditions are not ideal. I have a wood stove for heat. GE refrigerator built in 2001 that I'm currently trying to find out the wattage it uses when it surges. I never use my microwave. A dishwasher that i rarely use. Also it's not hot enough here to hang dry clothes so I have to be connected to the grid for my 220w clothes dryer. Really in the near future I think I just want solar to help with my electric bill. And I lose power every winter do to fallen trees. ( I have a generator too)

And yes I'd like to save money by buying quality stuff once rather than constantly upgrading.

This site has a ton of info and I'm learning a lot. Thanks again

No Problem, just lots to learn!

Off Grid and Grid Tied are very different creatures, I live off grid, so others might correct me later, but I understand and even helped set one up, so let me give it a shot.

Grid tied systems, come in 3 sorts.

The first is when strings of panels are sent to a central inverter, the strings of panels must be above the line voltage and the inverter adjusts the voltage and synchronizes to the line voltage and back feeds the grid.

The second has micro inverters on the back of each or every other panel and they are combined run back to the grid.

In the first 2 types there is no electric if the grid goes down. It is likely you can come close to paying for these systems over their life times and may even save a few dollars. They are a good hedge against electric rates rising particularly if you can get a long term contract with the electric company. 

There is some effort to make a small amount of electric available when the sun is shining by a couple of the inverter companies, as well as a high voltage charge controller that might make 120 available through some inverters.

The third type is a hybrid inverter which would have battery bank. You charge the bank and can sell back to the electric company. These are more expensive to begin with then add the cost of batteries which will require being replaced and the cost of keeping the batteries charged (times when you could be selling back to the grid) and they become money hogs in my opinion.

Given that you are not in the best location for solar, it would be pretty much a safe bat that all of these systems will cost you more money than they will save you!

There is nothing wrong with 100 watt 12 volt panels, I lived for several years with a 12 volt battery bank!  Just understand that it doesn't have any value with the grid tied system, If you purchased 2 - 140 - 165 watt panels you might be able to use them with a micro inverter. I don't know enough to say weather it would work well or could be strung with other micro inverters.

Batteries are purpose units, you could by a 12 volt battery or 2 - 6 volt golf cart batteries and have a nice 12 volt system, but it would not have any value in your whole house system, they would be too small unless part of a string and you don't mix old and new batteries. Like wise your off grid 12 volt system inverter would be too small to have any value for a hybrid system. Hybrid systems generally work at 48 volts, an inverter designed for 12 volts could not be used with such a system.

You could and should try a small system if you are interested. You could also check the solar isolation of your exact location to see if you have enough sun falling on you location to make grid tied an option and figure out the real cost to you. You might also check with you power company and find out how they handle net metering particularly if they are municipality owned (they are exempt for Net metering laws)

I've found some links to inexpensive panels and charge controller for a guy with a cabin system inthis thread;

http://forum.solar-electric.com/discussion/350713/my-trojans-did-not-last#latest

littleharbor2

My cordless tool battery charger seemed to work fine on a MSW inverter. Problem is it totally ruined all my batteries. Price out replacement batteries. They are going to cost more than a small sine wave inverter.

fauss

Thanks photowhit you've cleared up some questions. Looks like grid tie is not feasible for me yet. I'll probably just make my shed off grid and not worry about my house. So a single 12v deep cycle battery or two 6v golf cart batteries will work for a few lights, a radio and to charge other batteries and devices.

vtmaps

fauss said:

So a single 12v deep cycle battery or two 6v golf cart batteries will work for a few lights, a radio and to charge other batteries and devices.

Beware of "12v deep cycle battery".  There are a lot of batteries labeled "deep cycle" that are NOT suitable for your application.  Do research and ask here before you spend.

--vtMaps

m151

20kwh sounds like a lot! I would try to get down to 10kwh. Keep your experimental system as an emergency back-up. Then if your goal is to build up slowly you could add a QUALITY micro inverter and panel(s) as funds become available. That's been my plan, but until I pay off every dollar of credit I figure that solar can never offset as an investment.

fauss

Ya 20kwh a day is a lot! It doesn't make sense for a 2 bedroom home. My refrigerator according to my watt meter uses 3.1kwh a day. So where is all the power going? It would be difficult to meter my oven. My base board heaters are off. I dont own a tv or a computer I rarely have lights on and I just switched them to led 7 watt bulb. Maybe my next electric bill will be smaller now that I'm cracking down on my usage. Any other suggestions about conservation would be helpful. Thanks

Photowhit

You've got the right idea, Water heater is in the top 3, do you have it set very high? Could you switch to a heat pump type,GeoSpring(?), maybe put it on greybox timer to come on for an hour in the morning and an hour in the evening. even a minor drip in hot water will run the heater exponentially. Old style projection TV, or big plasma. LED TV's run much lower wattage...

BB.

Identify your loads. Turn off all your branch breakers and turn one on at a time.

The newer utility meters will usually flash the instant power usage once every few seconds on the display (1 kWatt = 1,000 Watts).

Intermittent/cycling loads you may not see (fridge/electric water heater).

Note that a 20,000 WH per day load / 24 hours per day = 833 watt load (24 hours per day).

So a forgotten smallish load (under desk heater, dehumidifier) running 24 hours per day can really add up.

You can get a whole house monitor like:

http://www.theenergydetective.com/

Can make the process much easier.

And your fridge could be replaced with one that takes 1.5 kWH per day or less.

Probably lots of chances for conservation.

-Bill

fauss

Thanks for the responses guys. I've done a lot of changes so I'm interested to see the difference on my next bill.

fauss

Any suggestions on a battery? Brands? 6v Golf cart batteries are spendy but if it what need then ill use them

Photowhit

They run about $85 at Costco and Sam's Club. Likely the best bang for the buck. 'Marine' deep cycle typically don't last very long. I think there are a few 12 volt deep cycle, with smaller capacity, but they are in the mid $150's -200,  Trojan 1275.

You can find smaller true deep cycle batteries, but since Golf cart batteries are mass produced, they tend to be as cheap or cheaper, until you get to pretty small batteries.

bill von novak

fauss said:

Any suggestions on a battery? Brands? 6v Golf cart batteries are spendy but if it what need then ill use them

6V golf cart batteries are the CHEAPEST batteries you should be considering.  Trojan T-105's are the standard.

fauss

Can some one point me in the right direction for 4 or 6 gauge wire and connectors (between the cc and battery bank). Will any 6 gauge wire work as long as it's not a solid core? Seen wire at a hardware store for under a buck a foot. Then found wire for solar for double that online. Any difference? Also do I use the same gauge between the batteries? (2 x 6v 208 ah in series) thanks

radtech8806

Fauss I wanted to chime in here for a moment and add my two cents worth if you don't mind.  I'll tell you up front that I am not an expert in solar power systems, but I have over 30 yrs experience in electrical and commercial radio telecommunications systems and I wanted to point out a few things that might save you some problems down the road.  If you are unsure about the correct wire type and size to use for your charger leads and battery leads you can google (wire ampacity) online and you can get a list of the wire types and sizes and how much currant they are rated for.  Keep in mind that interior wire will not last long if it is used outside in sunlight.  Another point is choosing wire size.  As a rule of thumb,  I always suggest using wire that is capable of carrying 30 percent more than your highest expected load.  I do this for two reasons. 1:  The extra capacity prevents heat buildup in the cables when you are running at high load, which means you won't be wasting energy dew to resistive heat loss. 2: If cables heat up they expand which can cause them to get loose at the connector lugs.  I also recommend that when you do decide to put your system together that you use that same 30 percent rule with you inverter.  I can't begin to tell you how many two way radios and power amps I have repaired over the years simply because they were setup to run at full power.  The constant heating and cooling caused by varrying loads was the problem.  When equipment is run at or near it's maxo ability, it gets hot and like the wire, the solder on the circuit boards expands and contracts.  The solder will eventually develope fatigue cracks and the unit will fail.  No electronic devises will last long if runs full out even intermittently.  Be sure to use copper wire.  It is less resistive than aluminum so you can use smaller cables than with aluminum.  One thing I have been looking at very closely is the inverts that are pure sine wave and transformer based.  They seem to work best with inductive and heavy capacitive loads.  They can take a large power surge like an a/c unit or washer and drier would reqire.  They can also hold that surge for several seconds while high frequency true sine wave units are only good for couple of seconds or less.  That is a major plus if you want to run heavy inductive loads like a/c and well pumps.  I hope this will help.  All the luck to you.