Solar powered Hot Tub?

[Interplayfun]

We are getting bids to put solar photovotaics on our roof to produce electricity . . . California provides a rebate for about 30% of the cost + the Feds and Cal state provide tax incentives for another 10% in the year of installation . . . not bad.  Everyone has been interested in the tub and its electric usage.  We've gotten two months of PG&E bills and its run between 40 and 50 bucks both months.  A couple of people have recommended a separate solar panel array + battery just for the tub.  Don't think we will do this as it's a bit more expensive (about 3000 more) and it's already pricey to put up solar.  Anyone out there using solar electric to power their tub?  Advice appreciated.

[Dr. Spa™ Ret.]

Why would you use batteries if you're connected up to PGE's grid? When power is generated and run through a converter you can run it backwards through your meter, back into PGE's grid....... Your electric meter then runs backwards, and if at the end of the month you generated more electricity than you used PGE cuts you a check.

[Interplayfun]

According to literature and info session we attended by P,G&E . . . no check will ever be cut (unfortunately).  The best you can do is net out at zero, not owing anything for electrical.  If you provide more power to PG&E than you use . . . tough!  PG&E pockets the difference.  If however, you use more than you produce, you'll get charged at the regular rate.  The claim is that this system enables PG&E to maintain the power grid.  Batteries are indeed not required if you have grid tie back, they are handy in the event the grid goes down due to quake, etc.  We've already decided not to go with batteries (too expensive).  Just wanted to get a sense of how electric charges add up with solar + tub.  Also, how big a system is required to net out at zero.  We've been advised that we need at least a 3.5kw system . . . without the tub is would be 2.5kw.

[drewstar]

$3000 more?  I could run my tub for 10 years before hitting the "break even" point (assuming rates don't change.)

Do they provide any info on the life expectancy of the array and set up? Any maintence costs?  Or once this unit is in, you can completely forget about it?

[Interplayfun]

Well . . . at $50 per month to run the spa (that's our first three months with the spa . . . per month average above our previous average) . . . it would take us only 5 years to payoff  :-/.  Still, doesn't make sense to do it strictly based on the numbers.  Maintainance costs are virtually zip, 25 year warrantly on the panels, 5 years on the whole system.  Once its up, you are good to go.

[drewstar]

5 years if rates stay the same, less as rates rise.

5 years isn't too bad. espcisllay if the equipment is rated for 25.  (The storage cells will last the long? )

But the intial outlay of 3K...that stings a bit.  

[Interplayfun]

No storage batteries as this is a grid tie back system.  Otherwise, you don't get the state rebate. . . I am curious to know if anyone else out there has solar electric up and running with a spa.  So far, answer seems to be no

[Dr. Spa™ Ret.]

I've seen it done. I have a customer in San Francisco that runs his building on a PV array. 3 apartments, two small retail stores, and a 500 gallon traditional wooden hot tub. It's been a while since I saw it, but as I recall he said it was about $20k to install and he averages a $10 electric bill per month.

He was talking a 10 year pay back, though I don't remember if that took into consideration what he was charging his tenants for electricity.

As a side note, I've heard that if only 25% of the roof tops in the US were covered with PV panels, that would supply our entire contries electrical needs.