I am interested in installing a solar power system to power my home during the day. At night, the system would get power from the grid. Is this possible? Economical? Crazy? How much would a system like this cost?

Any input you guys can provide is greatly appreciated!

If you are OK with spending $40 - $50,000 on a system that will give you $1200 worth of power per year than go for it.

Solar power works and is easily available but it is expensive to have a system large enough to get a decent amount of power from.

Now remember, this is based on trying to please your average power hungry American power needs. If you can reduce your electric use to a very low level (lights and a few simple items) solar may be a good choice for you.

If you want AC, Hot water, hair dryer, electric stove and an electric tooth brush you better have some serious $$$$ to spend on a solar system.

After tax credits and rebates, a professionally installed turnkey PV grid-tied system can be had for $4.50-5.00 / watt.

Oddly enough, if you're using a ton of power, solar tends to make better economic sense because you'll be in a higher tier. If you're routinely in a .30/kWh tier the ROI for sunny states starts looking pretty good.

OP, what you may want is a grid-tied system. Excess power is fed into the grid and you get credit. At night you pull power from the grid.

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Yep - grid tie.  In TX with the current credits/incentives the pay back for a system that meets your average power requirement may not be too outrageous.  For most apps a grid-tie is about the only thing that comes close to making economic sense.

I'm in texas and just setup a small solar system a few weeks ago. I went small, simple and cheap so am using 80 watt panels tied to a grid tie power inverter. Did the installation myself to keep cost down and so far so good. I ordered my first panels off ebay and they were very inexpensive but are working fine. Eventually I'd like to install 6 of the 80 watt panels so I have about 500 watts of solar power.

Do you plan on eventually running your AC with it? How many panels would you need to run an AC?(central ac and heating)

Why is solar so expensive? Is it panel costs? Installation costs? Other costs?

give up the idea of running AC.
Simply do the math. see how many amps you draw or watts you use each day/month
Then grid tie for best results...if you tried running AC from a battery bank....well that battery bank would be huge and tweaking in at about 10,000-15,0000 dollars. Because one reason is that you dont want to pull more than 20% of the actual battery banks charging capacity down for longest life.

after you have done the math go to sunelec.com and look at thier grid tie packages. if you do it yourself, you can save some major money. But your question is very hard to answer without more information. You're simply asking "How long is a piece of string" without more information it cant be answered..

I can't afford a big system so will keep mine fairly small which means no way it would power all my electricity usage. I'm just using it to help offset high utility bills and have a backup source of power for emergencies. I have to admit though it is pretty cool to go check the grid tie power inverter and see how many watts are being produced thru the solar panels. I just need to save up for more panels so I can get it up to my goal of 500 watts.

As for installation, it wasn't too tough. I have no background in electrical stuff and I did it all myself. I just read up on it thru websites and took it very slow and check and rechecked everything before I hooked it all up. As for cost, the small 80 watt panels are not too bad. You can get them for $200-$300 each off ebay. Cabling isn't cheap and doesn't use standard connectors but not too bad. I'd recommend going with the 10gauge wiring to minimize power loss from the panels to the grid tie power inverter. I'd also recommend mounting the panals as close as possible to the inverter. The  inverters can be pretty pricey depending on which one you go with.

Is this 20% # true?  I thought the number used for system planning was 50%?

Confused,
-Slice

it is. standard batteries shouldnt be drained more than 20-25% but the batteries in solar systems are designed to go to 50%. thats the whole point in deep cell batteries.

Mabe in a poorly designed solar system.

People who keep their batteries 10-15 years usually baby them with an 20% +/-, and are the exception.  If you take them down to 50%, you lose a lot of life (think 5 years).

Deep cycle is designed to deliver over time, versus the relatively instantaneous and short starting cycle in a typical automotive battery.  The depth of discharge is still an issue with all conventional batteries.  LiIon/LiPo change this, but are out of reach for a typical cost constrained stationary power system.

There are other battery options, but they aren't always practical.  Nickel-iron batteries are the next thing to indestructable with virtually unlimited cycling and close to zero maintenance.  The problems are that they're expensive, inefficient, bulky, and have a relatively high self-discharge rate.  But they are well suited to solar applications with daily charge/discharge cycles, and if you want batteries that'll outlast your panels' 25 year warranty, they'll work.

For the price of Nickel-Iron batteries you can buy multiple sets of lead-acid Interstate UL-16HC's.

FWIW, I predict there will be a significant breakthrough in electrical storage/generation technology in the next ten years similar to the game-changing progress in electronics with the introduction of the transitor and microchip.

I could be wrong but I was told that to get the longest life out of any type of battery other then nickle-iron is to not disccharge them past 20% of thier capacity, regardless of what type of battery it is. Sure they can go down to 50% or even more, but sulfation kicks in and thery begin their creeping journey to death....overdischarging really can dramatically shorten the life of a battery. I'm far from a battery pro, so I could be wrong but I adhere to the 20% rule and have golfcart  batteris last 10 years or more while other people toast theirs in 4-5-6 years

There are folks out there who are still using Edison Nickle-iron batteries that were made in the 1930's... they came from a railroad signal switching box....I wish I could afford a set of those buggers!
I ve been told Nickle-Iron batteries can also be washed out and new electrolyte added and they are ready to go again....nice deal.
Nickle-Iron appears to be the holy grail on batteries....for now I use golf cart's

I was recently reading an article on deep-cycle batteries because I purchased a boat with a trolling motor.

The author said that the best way to get a long life was to almost fully discharge them before recharging.

I'm curious as to opinions here, as I just purchased two new D.C. batteries and want them to last a long time.

(sorry for continuing the thread hijack).

The author is wrong.

The deeper you discharge them, the shorter their life expectancy.

This is a question on the exam to become a registered public land surveyor in the state of Tx.  The answer is "twice half it's length"

20% depth of discharge max for a long life.

People who run deep cycle batteries down to 50% or more are people who replace battery backs frequently.  I know people who live off battery banks who have had the bank almost 15 years, but they never go more than 20% discharged.  I think 15 years is an exception, rather than the rule, even with good care.

you do understand we're not talking about taking the batteries down to 50% every day or even every other day, right? deep cell batteries dont suffer any decrease in longevity because they were drained to 50% a couple times a month.