Is it now possible and what would be the cost of making a typical 30-year-old house capable of producing enough electricity to power all appliances plus air-conditioning in 90-degree-plus Texas heat?

"How long is a piece of string?"

In short, you're asking a VERY open-ended question with ZERO actual specifics as to what your limits in money, available manpower, time, and legal.

CAN you do it?
Yep!
You're going to be making a sizeable investment in solar and/or wind equipment, battery storage, and power management equipment.
You may also be limited by your state/municipality as to the maximum size of your power installation.
You may be required to grid-tie.


And on...and on...and on...

...and perhaps Google “Net Zero Energy House” to begin to gain some basic understanding of this subject.

It depends on so many factors but generally speaking it will be much more economical to first address the possible energy inefficiencies of your home such as possible upgrade insulation address air loss with caulk etc. more efficient HVAC such as possibly geothermal and water heating such as heat pump type or with desuperheater from geothermal unit and duct sealing .. To less extent appliances but probably just as they become unserviceable. Although an estimate if you didn't do any any changes to your current home would be to gather your utility bills for at least a year to determine average energy use and you would have to convert any gas used or other forms of energy such as oil or wood in BTU S to equivalent amount of electricity to create that cost or amount of energy. You could then see how many KWH killowhat hours of electricity you would need to produce in a year to break even in cost. Then figure the general high cost of batteries a grid tied system perhaps with battery backup but remember if you are grid tied you will be reimbursed a different amount than you pay so wanting to be net zero is different from being zero energy cost. You would likely need to produce much more than you actually use if you are reimbursed a lot lower than you pay to be net zero cost. You can go to a website such as Wholesale Solar or ALT E armed with your utility bills etc and they could help you determine the size and type of system and cost and remember for rest of this year you receive 30 percent federal tax credits if in use by end of the year. If you happen to be all electric to be net zero but not zero cost you can take the Kwhr for whole year and use hours of useful sun light fo see what size system you would need . For instance in my area there is about 5 sun hours per day.. If I use $200 worth of electricity per month at .10 per kwhr I need produce an average of 2,000 kwhr of electricity per month or an average of about 66 kwhr per day divide by the 5 sun hours per day. so I would need about 13.2 kwhr system. A system of this size is about $20,000. Then they cost of installation might well be close to the cost of system lets say$35,000 total. Subtract the 30 percent credit and you are left with a cost of $24,500 that would take 10 years to get to the break even point. Ofcourse if you do a lot of the installation the payback would be sooner and consider the cost of energy will increase payback will likely be closer to 7 or 8 years.

Electricity generated through coal is going expensive. power cuts and Dependence on DG is causing a lot of damage to the environment. the demands for the electricity is increasing day by day. Now we need a other option to generate electricity. and the other option is that generate a electricity through the solar power plants. its safe and effective as compare to the coal electricity. total cost of installing a solar power plant is average per kilowatt is 60,000 and now it depends on you that how many kilowatts you want in your home. 5 kilowatts is most enough in a home to operate all the appliances including ACs. Thanks Nishan Singh

True, but the folks who generate their wealth via the fossil fuel empire will not give it up even knowing that it is destroying the planet. Money and power has always been more important.

Nish, but he's not looking to operate in an "emergency" mode.
He's basically looking to full-time power his home off solar/renewables.

This means that he needs to figure out what his overall draw is throughout the day, hopefully using  a day with maximum draw as is load ceiling.
Then he adds a safety margin of a few percentage points.
He then needs to build a system that can satisfy that on his lowest generation days and store power to account for multiple days in a row.

The AVERAGE draw of a US home is about 1.2 kilowatts per hour (or 1.2 kilowatt hours) or about 30 kilowatt hours/day.
And remember that your solar panels are only really producing significant power 5-6 hours a day.
So BARE MINIMUM to keep things going you need to have a 5-6 Kilowatt system and hope to God that you are getting maximum production.

You aren't though.
So the industry standard is to triple (yes, triple) the size of the array.
And it's pretty linear.  A 5KW system will run you about $16K before any government kickbacks.
15KW system will run you about $45K before any government kickbacks.
I figure an 18K system will weigh in about $50K.

And that's BEFORE battery storage.
A Tesla Powerwall2 has about 13.5 KWH of storage.
So you'd need about 3 of them just to get through a single day.
And that system would run you about $30K

Likely you'd probably want to double capacity (if Tesla would even SELL you that many power walls).
So you're probably looking at $50-60K

So, figure $100K for a complete system, and be nice and include a small-property wind turbine for some additional generation capacity that ISN'T dependent on sunshine.

Now, "is it worth it" will  depend on your local price for electricity.
In Illinois (where about half our power is generated by nuclear), I've done about 30 KW hours on average.  With monthly bills weighing in around $65/month.
It's less during the winter, but I'll be nice and assume maximum draw of summer (with AC) 12 months a year.

65*12 = $780/year.

100,000 / 780 = 128 years to payoff.

So, such a system would be COMPLETELY infeasible for me.  It'd wear out before the panels would need replacement SEVERAL TIMES OVER.

Granted, with the cost of power increasing year over year, it wouldn't ACTUALLY be 128 years.  (More likely 85-100 years.)  But my point remains.

Now assume I'm the US AVERAGE (I'm about 1/20th.).

Suddenly I'm using 900-ish KWH per month and I'm going to be bumping into more expensive tiers with that much demand.
So, now, instead of spending $780 a year, I'm spending about $16K a year.

100,000/ 16,000 = 6.25  So about 6 years.
THIS is FAR more feasible.  Though the cost to replace the batteries  several times in the solar array's lifetime aren't factored in.
PW2's have a warranty of 70% guaranteed output at the 10 year mark.  If we've doubled-up as discussed earlier, that's STILL enough capacity go carry you around 2 days if you're frugal.
So, assume 15 years out of a battery array and a replacement at that time at a similar price point.
(Note: It's possible battery technology will be more efficient, have higher capacity, lifetime, be cheaper, etc by then.  But just for sake of argument, consider the cost identical)

150,000 / 16,000 = 9.375.  So just under 9.5 years of payment for a system that'll last 30+, barring damage to the array.

That's actually not bad.  And at the end of that 30 year period, you're looking at a system that's still outputting 75+% of it's original maximum capacity and is simply due for a storage upgrade again.

Now I've left out things like maintenance, panel replacement, etc.

But, for the most part, I've quoted fairly realistic pricing for an installed system.

Things I haven't covered.

Loan interest.  This I'm DEEPLY ignorant about.  But unless you're going to poop out a fat sack of cash, you'll be taking out a loan for this.

As noted, system maintenance and equipment replacement due to unforeseen damage (like panels after a hail storm).

Government kickbacks on solar systems.

In some places, you're eligible to get up to 30% of the cost of your solar array (but possibly not your storage system) back from the government.  Though some of these programs are shutting down.  These programs will pretty much do nothing but speed up the "time to repayment" of the system.  Though there may be some limits on the size of the system that can be built.  Meaning that you'd HAVE to go grid-tied no matter what.

Still, most optimal.

50,000 * 70% = 35,000




Now.  Hopefully I've given you good info and your eyes didn't glass over...

Also, for pricing for a solar system that'd fit ME?
We're looking at roughly a 1.3KW system for around $2800.
And a single powerwall2 (which'd be overkill).
Total cost. About $10K.

10,000 / 780 = 12.8205... years.

It's still economically infeasible unfortunately.
Generally anything under 10 years is considered "acceptable".
Anything under 8 years is considered "good".
Anything under 6 is considered "great".