The DIY World Store

How big of a setup do I need

Discussions about solar power and solar energy projects.

Re: How big of a setup do I need

Postby techman » Thu Feb 26, 2015 10:33 pm

Yes you can save energy by using solar panels and be on the grid.

What you could use is a grid tie inverter. This allows you to tie in your solar panels to the power grid. When the sun is shining you will be using solar energy.

When the sun is down (night) or cloudy, then you will use grid power.

No batteries needed.

You can also sell excess power back to the power company, if your solar power system eventually provides more power than you can use each day.

The down side to a grid tied system is that your power goes out when the power grid fails.

You could have a switch and some batteries to switch over in that case.

Hope this helps

And yes Techman = Troy :)
Site Admin
Posts: 1308
Joined: Thu Dec 22, 2011 11:49 am

Re: How big of a setup do I need



Re: How big of a setup do I need

Postby JimW » Fri Feb 27, 2015 8:59 am

Troy, people may want to check their local and state laws. Here in Oklahoma, if you have a grid-tie solar power system, you have to pay taxes on the power you sell to the power companies. For us it works out better to just go with no grid-tie and use separate wiring for solar and grid power.
Posts: 36
Joined: Tue Feb 10, 2015 2:41 pm
Location: Oklahoma

Re: How big of a setup do I need

Postby techman » Sat Feb 28, 2015 12:11 pm

Good point, thanks for sharing that. I never had to think about it because the power grid is not an option for me at all anyway. There are no wires out here.
Site Admin
Posts: 1308
Joined: Thu Dec 22, 2011 11:49 am

Re: How big of a setup do I need

Postby john3voltas » Mon Mar 23, 2015 3:11 am

Thanks for your reply.
I actually don't need to go completely off-grid. But with this economic crisis I surely would be glad if I could save some money.
Let me check if I got everything straight.
I will need:
- PV solar panels (the more the merrier)
- power inverter
- batteries (optional)
- charge controller (optional - only needed if I go with batteries?)
I think I may have said it earlier but I'll say it now just in case. I live in Europe, more precisely in Portugal.
Having said that, where would I find the best PV solar panels (even if I have to make them myself)?
And what kind of power inverter should I buy? Is that choice tied to the amount of watts that the solar panels will provide?
And I would like to know where to shop for these :)
Thanks in advance.
Posts: 7
Joined: Mon Feb 09, 2015 2:50 am

Re: How big of a setup do I need

Postby JimW » Mon Mar 23, 2015 7:25 am

John, Troy may be able to answer your questions better, but...
Ebay is one option for solar cells. Look for $1US per watt, or less if you can find it. At $1/watt that will run you $1000 for each kilowatt, plus the costs for the charge controller and batteries. If you want ac power it would be best to get a pure sinewave inverter. Most that you see are "Modified sinewave", if it doesn't say, then it is probably modified sinewave. A modified sinewave is a stair-step forming something like a sinewave, but it can damage equipment and really shouldn't be depended on for long term (and, unfortunately, that's what I've got!!!!).
Buying individual cells and building your own panel will work, it may not look as pretty as the factory built panels, but it will still work. Troy has some video's where he built his own panels. Doing it that way you may be able to get below $1/watt.
The problem with grid-tie is that if the grid power goes down, so does your solar power. Unless you have a switch where you can disconnect from the grid, then, unless you have the battery backup system, you will only have power during daylight hours. If you are going to have the battery system, you may as well not connect to the grid and instead have a separate lighting/power system in your house. That could add to your total cost, but you would at least know that when the grid goes down you will still have lights and power that you can use.
Like I said, Troy can probably give better answers, and he probably knows some places other than ebay where you might check.
Good luck, and I hope you manage to get a good setup!!
Posts: 36
Joined: Tue Feb 10, 2015 2:41 pm
Location: Oklahoma

Re: How big of a setup do I need

Postby hi_tech_guy_18 » Thu Mar 26, 2015 4:45 am

I would recommend a grid tie system but still uses battery's for off gird mode.

Some of these Hybrid systems can make you money on sunny days

Hybrid systems will charge you battery back first then convert the surplus to the electrical grid
if your not home this can make the power company's pay you for a change

When your home it will use the battery for power until they run low then connect you home to the grid to recharge the battery off peek (Night time when Electricity rates are cheaper 1AM till 8AM)
even on bad overcast days you still have a choice of the night time rate or the grid peek + any solar generated at a lower level.

When you think about it this treats the power gird as a UNIT Trade Market . (You can see the Electrical gird being a sort of "Unlimited" AUX battery)
However the key to it is getting Your system to Make more power than you use so on overcast days the extra units made on sunny days will cover you on the real bad days and nights
Even Extensions to the system so you can grow it much larger so even on overcast days your home is still making more than it using is a later bonus
(Car port gets it own solar array, Fed up of the garden Just cove the whole back yard with floor laying solar panels border to bonder this over sized array will help you out on overcast days but they have to be monocrystalline for better higher temps efficiently's for when the suns out - winter time you can use it as a passive solar heater due it so large and sitting on bricks for the air gap)
Posts: 120
Joined: Tue May 07, 2013 6:46 pm

Re: How big of a setup do I need

Postby techman » Mon Mar 30, 2015 11:50 am

JimW had some good points.

I should add that if you go grid tie instead of batteries then you need a grid tie inverter instead of a solar charge controller.

If you go with a dual system with the switch as Jim mentioned then you need both. has always been the cheapest place next to ebay that I know of
Site Admin
Posts: 1308
Joined: Thu Dec 22, 2011 11:49 am

Re: How big of a setup do I need

Postby NazikuKaido » Wed Jul 22, 2015 4:49 am

john3voltas wrote:Wow, I just noticed that techman == Troy. Which means that I am talking to THE man himself :ugeek:
Thanks for sharing your knowledge. :)
So, here's my challenge.
A 145w LED TV which is usually powered on for ~7 hours during weekdays and 12/14 hours on weekend days.
The TV will be mainly sucking power only from the battery because it's used at night.
145w x 14h = 2030wh
This means that for 14 hours/day I will have to be ready to spend more than $800 only on batteries to get around 6000Wh, which will allow me to spend circa 70% of my batteries. Besides, a small solar panel won't be able to keep the batteries charged day in day out, right?
Correct me if I'm wrong but a 200w panel in optimum sunlight conditions will recharge 200w per hour right?
Which means it would take more than 10 hours straight of perfect sunlight conditions to recharge 2030w, right?
If the above is true, could I somehow use both the solar power AND the grid power to power up my TV?
The idea would be to save as much as I can with the solar panel but still be able to run the TV on winter days?... :(
Something that would keep an eye on the battery consumption and that would bypass the battery as soon as it gets to only 70%. From then on it would get power from the grid.
I guess going off grid is a bit farfetched in my case (top floor of a condo). I guess all I can do is use some solar power to save on the grid bill, right?

Wow, nice idea! I think the 200w panel doesn't have to be the optimal radiation condition. It is a limitation of the material to convert solar to chemical energy in the battery.

Thus, it doesn't have to be perfect sunlight and it is even more better.
I am the best greatest ever
:shock: :? 8-) :twisted: :lol:
Posts: 13
Joined: Wed Jul 22, 2015 4:17 am


Return to Solar Power Discussions

Who is online

Users browsing this forum: No registered users and 3 guests