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Discussion Starter · #1 ·
I am completely ignorant of how watt hours and stuff works. I know that last month we used like 1600 kilowatt hours on our electric bill. Im looking at solar panels and am seeing them rated at the usual 60w, 85w, and some 200w.

Anyone know how you'd calculate how many panels you'd need to produce the 1600kwh?

Im not trying to get down to the nitty gritty but Id like to know how you figure this stuff.

I saw a guy on youtube who had one panel on his roof and with the inverter and stuff he had $250 in the little system but it only ran 2-5w light bulbs for a week. So it probably ran 2-60w bulbs for a day? or 2 hours? LOL

In the future Id like to have a bank of say 12-24 2' x 4' panels in a bank here on the property to supply enough power to run everything including the air conditioner.

Just looking for some ideas on how you figure this stuff up watts and watt hours and stuff.

* Just to add: I pretty sure I have a grasp that 1000 watts is a kilo watt. I just get confused when they throw the "hours" on the end of it hehe. yeah 1600 kilo watt hours last month.
 

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A heater, rated at 1000 watts (1 kilowatt), operating for one hour uses one kilowatt hour of energy.
Using a 60 watt light bulb for one hour consumes 0.06 kilowatt hours of electricity. Using a 60 watt light bulb for one thousand hours consumes 60 kilowatt hours of electricity.
If a 100 watt light bulb is on for one hour per day for 30 days, the energy used is 100 W × 30 h = 3,000 W•h = 3 kW•h,.
In your case which seems very high 1600 kilowatt hours per month (30 days) = 53.33 kW per day.
Say it was sunny for 8 hours then you would need to collect 53.33 kW in 8 hours
Or 53.33kW/8hours =6.67 kW•h
Using 100 watt solar panels you would need 67 panels. So you could have power at night or when it’s not sunny you need to store this power in batteries unfortunately when charging a battery some of the power is wasted heating the internal resistance of the battery. Turning the battery power to household mains using an inverter also involves waste. If you get more or less sun per day this would also affect the number of panels you would need. You would need more panels in the winter than in the summer just collect the same power per day.
 

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You can see you would need a huge bank of solar panels to continue to use the same amount of electricity as you currently do on the grid. Most people are going to find it is not economically possible to build an array to satisfy what they are currently using.

Instead, you can save tons of money, and actually make it possible to live off the grid by scaling back how much electricity you use. Both in terms of being conscious of behavior (remembering to turn off the lights) as well as using efficient appliances and lighting devices.

A dollar spent on things like fluorescent bulbs, high efficiency refrigerators, washing machines, etc. will equate to many dollars saved on a smaller solar array, less batteries, smaller inverter, etc.
 

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angel waiting
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You can see you would need a huge bank of solar panels to continue to use the same amount of electricity as you currently do on the grid. Most people are going to find it is not economically possible to build an array to satisfy what they are currently using.

Instead, you can save tons of money, and actually make it possible to live off the grid by scaling back how much electricity you use. Both in terms of being conscious of behavior (remembering to turn off the lights) as well as using efficient appliances and lighting devices.

A dollar spent on things like fluorescent bulbs, high efficiency refrigerators, washing machines, etc. will equate to many dollars saved on a smaller solar array, less batteries, smaller inverter, etc.
I agree with the above poster and will tell you after having done years of research on solar and wind you need to cut your cunsumption back. The systems you would need and the batteries you would need to go completley off grid would cost you thousands of dollars. Just because a solar panals says it produces 200 watts doesn't mean you will produce that amount all of the time. You would need 5 200 watt solar panals just to produce 1KW of power and that's only if it is producing at full capacity all the time. Cut your consumption back first then invest in solar unless your filthy rich it just isn't an economical viable source of energy unless you learn to live with less energy first.
 

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Discussion Starter · #5 ·
Thanks for the replies folks!

Yes, were already cutting back. Believe me the 1600kwh was for a slow month here with an electric bill of $168. Usually the bill is around $225 and in the winter can get up to $325.

Of course that included running the AC in the summer and electric heat in the winter.

We have already seen a decrease in usage though as our last child has moved out and its just the wife and I. We have recently changed all the bulbs to the twisted flourecent ones and Im going to make a clothes line out back to hang the laundry and not use the dryer for clothes when possible.

Any idea of what I might be looking at as far as usage with the AC/Heat not in the equation? We are thinking that we could have solar for specific needs like a solar charger for the horse and livestock electric fences. Maybe a panel to run a well pump and such.

Withthe research Ive done I do understand that it would be difficult to get off the grid while using the ac and dryer along with other high draw items.

I would like to provide for the lower use items such as lights and maybe the TV using a solar/wind combo or something.

Your posts have been very helpful for sure.
 

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A heater, rated at 1000 watts (1 kilowatt), operating for one hour uses one kilowatt hour of energy.
Using a 60 watt light bulb for one hour consumes 0.06 kilowatt hours of electricity. Using a 60 watt light bulb for one thousand hours consumes 60 kilowatt hours of electricity.
If a 100 watt light bulb is on for one hour per day for 30 days, the energy used is 100 W × 30 h = 3,000 W•h = 3 kW•h,.
In your case which seems very high 1600 kilowatt hours per month (30 days) = 53.33 kW per day.
Say it was sunny for 8 hours then you would need to collect 53.33 kW in 8 hours
Or 53.33kW/8hours =6.67 kW•h
Using 100 watt solar panels you would need 67 panels. So you could have power at night or when it’s not sunny you need to store this power in batteries unfortunately when charging a battery some of the power is wasted heating the internal resistance of the battery. Turning the battery power to household mains using an inverter also involves waste. If you get more or less sun per day this would also affect the number of panels you would need. You would need more panels in the winter than in the summer just collect the same power per day.
typically after battery charging and inverter losses you only get about 60% of the rated power of the panel to actually use. so if you need to actually use 100 watt hours then you would say 100/.6 = 167 watts worth of solar panel.

also i think 8 hours a day average sun is a little optimistic. here in virginia i'm lucky to get 4.5 and i think the average when you count cloudy days is an average of 3.5 hours of sun per day

so if you count cloudy days in the equation the numbers get really fun
53kwh per day/3.5 sunlight hours = 15.1kwh useable
15.1kwh/60% efficiency = 25.16kw worth of solar panels
or put another way 252 solar panels
solar is currently selling for around $1.83per watt so just the solar array to feed 1600kwh/month would cost right around fourty six thousand dollars... then you need batteries, charge controllers, mounts, cableing and inverters.

personally i recommend you start with efficiency.
 

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Discussion Starter · #7 ·
typically after battery charging and inverter losses you only get about 60% of the rated power of the panel to actually use. so if you need to actually use 100 watt hours then you would say 100/.6 = 167 watts worth of solar panel.

also i think 8 hours a day average sun is a little optimistic. here in virginia i'm lucky to get 4.5 and i think the average when you count cloudy days is an average of 3.5 hours of sun per day

so if you count cloudy days in the equation the numbers get really fun
53kwh per day/3.5 sunlight hours = 15.1kwh useable
15.1kwh/60% efficiency = 25.16kw worth of solar panels
or put another way 252 solar panels
solar is currently selling for around $1.83per watt so just the solar array to feed 1600kwh/month would cost right around fourty six thousand dollars... then you need batteries, charge controllers, mounts, cableing and inverters.

personally i recommend you start with efficiency.
Good stuff. Again, already starting on the efficiency. Just wanting to cut the costs some more and prepare to have a refrigerator should there be no power. :D:
 

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Thanks for the replies folks!

Yes, were already cutting back. Believe me the 1600kwh was for a slow month here with an electric bill of $168. Usually the bill is around $225 and in the winter can get up to $325.

Of course that included running the AC in the summer and electric heat in the winter.

We have already seen a decrease in usage though as our last child has moved out and its just the wife and I. We have recently changed all the bulbs to the twisted flourecent ones and Im going to make a clothes line out back to hang the laundry and not use the dryer for clothes when possible.

Any idea of what I might be looking at as far as usage with the AC/Heat not in the equation? We are thinking that we could have solar for specific needs like a solar charger for the horse and livestock electric fences. Maybe a panel to run a well pump and such.

Withthe research Ive done I do understand that it would be difficult to get off the grid while using the ac and dryer along with other high draw items.

I would like to provide for the lower use items such as lights and maybe the TV using a solar/wind combo or something.

Your posts have been very helpful for sure.
getting off the clothes dryer is huge, use a clothes line whenever possable. actually a good first step though would be to invest in a better water heater. the average energy star rated 40 gallon electric water heater consumes about 5000kwh per year or 417kwh per month. if you dont mind useing gas then i would say start with a gas water heater but the better solution would be to go with a solar water heater. you can actually build your own really nice solar water heater for about a thousand dollars if you dont mind doing a little work www.builditsolar.com has a ton of projects you can build yourself.

if you want to start off with something simple you might try building a solar oven. they can be built for almost nothing and they work great.
 

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Discussion Starter · #9 ·
getting off the clothes dryer is huge, use a clothes line whenever possable. actually a good first step though would be to invest in a better water heater. the average energy star rated 40 gallon electric water heater consumes about 5000kwh per year or 417kwh per month. if you dont mind useing gas then i would say start with a gas water heater but the better solution would be to go with a solar water heater. you can actually build your own really nice solar water heater for about a thousand dollars if you dont mind doing a little work www.builditsolar.com has a ton of projects you can build yourself.

if you want to start off with something simple you might try building a solar oven. they can be built for almost nothing and they work great.
OK now were talking! Being appliance specific works too.

Solar water heater good call!. Nah I dont mind doing the work. Im pretty handy that way.

As for the over Im planning an outdoor living area now and it will have the All In One smoker/stove etc... that was shared here from Mother Earth News.

Ill look into that link. Thanks a bunch.
 

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Good stuff. Again, already starting on the efficiency. Just wanting to cut the costs some more and prepare to have a refrigerator should there be no power. :D:
a fridge is another great project. a typical fridge uses about 2.3 - 2.7kwh per day.

you can convert a chest freezer to a refridgerator buy bypassing the thermostat. the easyest way to do that is to get a lagering thermastat (home beer brewers use them when they are making a lager beer) i think you can still buy them at northernbrewer.com for around $50

basically you plug the thermostat into the wall and put the sensor into the freezer then you just plug the freezers power plug into the thermostat and it will send power to the freezer when it gets to warm and cut power to the freezer when it gets to cold.

the one i built uses around .4 - .5 kwh per day

the reason for the great efficiency is because all the cold air doesnt fall out of the chest freezer every time you open the door unlike a typical fridge that has to re-cool down every time the door is opened.
 

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Now that you've already changed out all your lights to fluorescent, I have a suggestion: change to LED lights. Some of them are so bright you can't look at them, much better than they used to be, and they take very little power to run. Plus, no mercury [which the fluorescents have] and they last a long time.

For heat, since you are already considering solar look into hydronic/hot water baseboard heat. You can at least pre-heat the water for the system, if not bring it up to full temp, with a circulating system heated via solar panels.

Check your insulation/air leakage/heat loss, too. Sometimes weatherizing can make a big different not only in terms of how much you spend on energy but how comfortable your house is.

Homepower.com is the website for a magazine that caters to DIYers for solar, hydroelectric and wind power, among other things. Lots of information on their website and well worth a visit.
 

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Discussion Starter · #12 ·
More goos stuff. Yes, I think the $1k solar water heater will be my first project after summer is over as I want to get the chickens and goats going and have alot of work to do.

Just to add: I am a licensed HVAC Contractor here in SC. Not much is done with solar round here. I hope I can build it and possibly even sell it down the road.

This will help with the cost as I can buy the copper in the project from my supplier and not from Lowes or Home Depot.
 

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Hi All American. I now live off the grid and have been for almost 15 years. It is touchy now and then, but can be done, and I never get an elec. bill. I have 12 - 85 kyceras which go through two c-60 charge controlers and then into 18 t-105 trojan batteries. From there the power goes into a 12-25 invertor, which runs my tv., lights, fans, two desk top computers , large refer, freezer and water pump system. I also have a wind generator, which when the wind is blowing really helps out a lot. Then,,,,, on cloudy or overcast days, I have to start my 7k kohler gen. to help out. But , if you quit with the heavy use appliances , you would do fine. NO heating units , including toasters , irons and things like that help a lot. NO AIR condi. ever ! They suck the life out of your batteries , panels, and even your generators. Get tougher instead, and just use fans. Even if you double the amount of solar panels, you would still be short for that
 

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Some thougths...

Cooling is not easy or energy efficient. But solar heating is your friend.

If you get some metal drums and paint them black and have some extra mirrors in a glass enclosed box focused on them. You can make great heat sinks to bleed off of during the night.

http://solarcooking.org/bkerr/SWHeaterRev-1d.pdf

http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm

http://www.builditsolar.com/Experimental/experimental.htm


A Cool Tower can drop air temps from 100F to 80F and would only require a small pump.

http://www.i4at.org/lib2/aircool.htm


As someone said, LED light bulbs are better than anything else, even though they are expensive.

Consider making an area like a BBQ but solar powered for cooking.

Converting the sun's energy into electric through photovoltaic is good. But using the sun directly is more efficient and better.


Sierra Dave
 
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