To provide 100% of your electricity needs, you'll need to go one of two routes:

1. Proceed with a battery-less system and use a REP (Retail Electric Provider) that will allow you to 'bank' kWh that you put on to the grid (in excess of what you use during the day).

2. Make REP not a factor, and instead, do your storage with batteries - i.e., a battery-based grid tie system.

The 2nd option is much more expensive than the 1st.  You're best economic point will come with a battery-less grid-tie system, combined with a REP provide that provides for 'banking' unused (at the moment kWh).

Best regards,

Bill

I'd recommend you consider a grid-tie only system (no batteries) for maximum economic point, and relook at your numbers.

You should be able to get a system installed complete at $6.00 / watt.  At least this is the case in the Dallas area.

Cut your size down to 10 KW (DC), or less, to be able to take advantage of all rebates, incentives, and tax credits.  At this point you should be able to cut the installation cost in half - figure $3.00/watt your final project cost.

Look at what kind of 'banking' of unused electricity you can do with your electric provider.

Bottom line?  I'll bet your break even is somewhere at 10 - 15 years.

Also, consider a lease purchase arrangement (what I'm doing) such that you don't have any up front capital expenses.

I too have geothermal HVAC, and indeed it's payback is significantly better.  But all energy reduction actions will always prove to be more 'lucrative,' than self generating energy efforts.

Best regards,

Bill

If you want to own the system, you'll have to decide if $30K spent to generate 20 years of electricity is worth it to you (assuming a 10 KW (DC) system, and assuming project cost after rebates/incentives/credits nets @ $3/W).

You can use http://www.pvwatts.org to help make the decision.

For example, using PVWatts and using it's default assumptions, for a 10 KW (DC) system, for my geographic location, I'd save $1500 the first year (at 11 cents per kWh), and higher amounts in succeeding years depending on what future utility rates are.  If you assume rates rise 6% annually, the rough break even point is about 13.5 years.
 
The lease purchase option eliminates all up front capital and expense expenditures.  In return, you'll make monthly payments, at a rate guarenteed to reduce your kWh rate by 20 or 30% (depending on size of monthly payment you choose).  This is the option I chose.

Best regards,

Bill

A couple of additional notes here:

1. Most panel manufacturers have warranties for 20 or 25 years to produce at least 80% of nominal.  Many/most of the higher quality level panels installed today will be working forever, just at a reduced rate.

2. Inverter replacement needs to be planned for every 10 - 15 years.  This is another cash expense to plan for.

Best regards,

Bill

I went with a group from DFW Airport several months back to talk Exceltech in Ft Worth about their inverters.  The concept is to change from a single inverter for the whole panel array to individual inverters attached to each panel.  This is supposed to modularize solar arrays and allow people to build their arrays as they can afford it and reduce the upfront costs associated with wiring the single inverter for the whole array.

Another feature, that I may not be able to articulate very well, is it is supposed to prevent panels that are shaded in the late afternoon, for example, from degrading the performance of the whole array.  My understanding of single system inverters is the total performance of an array is restricted by the lowest performing panel.

As a result, I am much more diligent about monitoring my panels for egret bombs now.

I think the individual inverter per panel products are going to dramatically change the residential portion of the solar PV industry.

The big question most have is focused on the reliability of inverters in the same environment as the panels.

The DIY market will also be enhanced, as the inverter-per-panel product eliminates 600 V systems being put into residential structures.  Until now, 600 V systems were limited to putting into commercial structures only.

The inverter-per-panel product also makes the system more tolerant of design errors due to shading, angle and tilt differences from panel to panel.

Enphase seems to me to have the biggest market share.  Haven't heard of Exceltech's progress so far.

Should be an interesting next few years, as the well-entrenched design-based-on-central-inverters industry segment battles with the inverter-at-each-panel segment. 

Best regards,

Bill