If they can just get the solar roof price down a little more it will really start to make a huge dent. You can have a twenty KW power plant on your roof and store excess power in a battery bank. Run the house, charge the car, and sell power back to the grid. Combined with an ICF house and some good windows and you can go all night without needing to run heat or A/C.

Have you priced an 8D batt. lately? Prolly need about ten.

Powerwall is about 10K installed in my area, problem is getting one as they are in short supply. There are other battery systems that are less money but not quite the performance. Nickel-iron is a good solution as long as you make sure to vent the area they are in well. Also cheaper but take up lots of space. If you have a basement or cellar they can do a great job with less cost. If you are building or remodeling an entire house and the budget is 5-600K it isn't a huge part of the total project. I would not do the roof and batteries as an add on to my current house. I would do the house as a complete energy efficient package. I just wish the power company would pay back at the same rate they charge. In my area it would only take me about four years to pay back, even the high cost of the powerwall.

I had a 56' motorsailer for 29 years, anything less than a gel battery is a long term nightmare. The Panzer boys had it right.

Gel and AGM are good, no doubt. Of course Tesla uses Lithium. The biggest advantage to nickel iron over any others is the lack of memory. They can be pulled to zero, charged to 100% and back to zero or maintained anywhere in the middle with little or no long term effect on battery life or ability to charge. Old tech but very stable and long lived. Too heavy for sail boats or vehicles but fine to anchor down a house.

NIckel Iron batteries are proving useful in hydrogen production.
https://www.bbc.com/future/article/2...years-too-soon

thank you.

Also thanks to the poster who suggested motley fool.

To those a couple pages ago who were asking about “will I have enough?”

A philosophy/approach is the 3% rule.
what it means is, whatever your nest egg is, as long as you don’t pull more than 3% from it per year, you will be fine.
A read one article where the author ran simulations during multiple decades, including 1929, 2009, and you could do it.
Others have said 4% should be the rule. More conservative.

The 4% rule is the big one that seems to work over many 30 year periods. Unless you are a big spender in retirement, you'll likely end up with more than what you started with. Great if you had kids or a cause you care about. If you're single like me, not so much.

Endowments at universities and others use 4%. If they spend 4%, the additional investment income added to the principal compensates for inflation. Also, it keeps the ups and downs from eroding the buying power, over the long hall.

This is conservative.