My ROI is about 14 years, are there any other hidden savings that could help this make sense?

[Gasaraki]

if you have time of use rules, powerwalls can have their own roi.

if instead you have net metering, powerwalls are a convenience with the payoff being backup during power outages.

in both cases pws also allow you to use solar during outages.

in either case you can keep powerwalls out of the panel roi and assess their benefit and value to you (payoff from TOU and/or power during outage) separately

Yes... it really depends on where you are. People on this forum claim that time of use charging and powerwalls don't work together in California. OP wanted to shorten their ROI, I gave them a short answer.

 

[bob_p]

Don't install Powerwalls, only go for solar. Powerwalls are still too expensive and will drive the ROI out too far. Try to keep the ROI on your solar under 8 years.

Operating without PowerWalls would require a net metering plan to "store" the excess energy on the grid and then use that credit to purchase power when there isn't solar power.

PowerWalls provide the option for operating under other electricity plans - such as a free night plan, when you can use the solar and PowerWalls to reduce as much as possible power usage during the daytime - and push as much of your power usage to the free nights period.

Plus, PowerWalls allow you to operate off grid for extended periods - in areas with unstable power, or in our case, where there is a risk of extended outages after a hurricane.

If the intent is to only run under a net metering plan and be prepared to lose power when there's a grid outage (and not enough solar to provide power for the house), then PowerWalls aren't needed - and can significantly reduce the cost and ROI.

In our case, we wouldn't have installed solar without the PowerWalls. The alternative was for us to install a whole-home gas generator, to provide power during outages. With solar, there is an opportunity for a long term payback, after we hit break even.

 

[h2ofun]

Just talked to a contractor who is working with a customer who has solar and one battery. When we had our last power outage, they were very shocked their battery only last 4 hours. He is now installing a 22K generator for them.

 

[MorrisonHiker]

Just talked to a contractor who is working with a customer who has solar and one battery. When we had our last power outage, they were very shocked their battery only last 4 hours. He is now installing a 22K generator for them.

There shouldn't have been any shock since it's pretty easy to calculate how long the batteries will last. All you need to do is take your battery capacity in kWh and divide it by your average hourly household usage. Our Powerwalls can easily power our house over 48 hours straight with absolutely zero sunlight. We did a test last year and easily ran over 8 days on solar and Powerwalls, even with close to a foot of snow which covered the panels. We could run our house indefinitely on solar and Powerwalls, if necessary.

 

[h2ofun]

There shouldn't have been any shock since it's pretty easy to calculate how long the batteries will last. All you need to do is take your battery capacity in kWh and divide it by your average hourly household usage. Our Powerwalls can easily power our house over 48 hours straight with absolutely zero sunlight. We did a test last year and easily ran over 8 days on solar and Powerwalls, even with close to a foot of snow which covered the panels. We could run our house indefinitely on solar and Powerwalls, if necessary.

Just depends on what run your house indefinitely means? Can you run unlimited heat and ac? Ovens, etc? No way one can make this statement unless you want to live like a cave man.

Now, solar folks sell, and most customers think, a battery can run an entire house, let alone indefinitely. Very few are as smart as you.

Just giving you a real life story of a family, which I expect is more normal that we would expect.

 

[astrorob]

one thing about these ROI calcs is that they span so much time that things can and do change which are out of your control. for instance since i installed solar, the CPUC allowed the utilities to establish a new net metering plan, and PGE also changed their mind about the costs and peak/off peak times on EV2 (vs EV, and other current TOU plans). luckily the NEM change came with a 20-year grandfather but the tariff change came with a 5 year grandfather, which means my electric costs go from +/- $300 per year to +$1500 per year. that has really messed up my ROI horizon.

so IMO it's best to not put too much stock into "this is going to be paid off in 7 years" - could easily end up being double that time.

 

[MorrisonHiker]

Just depends on what run your house indefinitely means? Can you run unlimited heat and ac? Ovens, etc? No way one can make this statement unless you want to live like a cave man.

Now, solar folks sell, and most customers think, a battery can run an entire house, let alone indefinitely. Very few are as smart as you.

Just giving you a real life story of a family, which I expect is more normal that we would expect.

Our average running load for the house it less than 1 kW. We have evaporative cooling which uses very little electricity and hot water heat so yes, we can comfortably run the house indefinitely year-round with our solar and Powerwalls. Here in Colorado, we have over 300 days of sunshine a year and it's rare to have 3 cloudy days in a row. We can have 20 degrees and a foot of snow one day and then generate 45 kWh to 65 kWh of solar energy the next day if I clean off a few of the panels and then the rest slides off. Even if it is cloudy, our solar system often generates 1.5 kW to 3 kW and can power the house and trickle charge the Powerwalls. We have 4 Teslas in the garage and aren't living like cavemen.

If someone thought their battery would be sufficient and it ran out in only 4 hours, then neither the owner nor the installer did a proper load analysis. As I said before, it's very simple math to take the battery capacity and divide by the average household load to estimate how long the batteries will last.

Note that since the above videos were recorded, Tesla added functionality so that the cars will automatically stop charging if there is a grid outage and the Powerwalls drop to a specified level.

 

[h2ofun]

Our average running load for the house it less than 1 kW. We have evaporative cooling which uses very little electricity and hot water heat so yes, we can comfortably run the house indefinitely year-round with our solar and Powerwalls. Here in Colorado, we have over 300 days of sunshine a year and it's rare to have 3 cloudy days in a row. We can have 20 degrees and a foot of snow one day and then generate 45 kWh to 65 kWh of solar energy the next day if I clean off a few of the panels and then the rest slides off. Even if it is cloudy, our solar system often generates 1.5 kW to 3 kW and can power the house and trickle charge the Powerwalls. We have 4 Teslas in the garage and aren't living like cavemen.

If someone thought their battery would be sufficient and it ran out in only 4 hours, then neither the owner nor the installer did a proper load analysis. As I said before, it's very simple math to take the battery capacity and divide by the average household load to estimate how long the batteries will last.

Note that since the above videos were recorded, Tesla added functionality so that the cars will automatically stop charging if there is a grid outage and the Powerwalls drop to a specified level.

What you are doing is great, but clearly, you are the exception, IMO.

 

[spooky981]

Thanks for the help everyone. I've decided to go solar with an 8.16 kw setup for the increased home value, the immeasurable but helpful roof shading, and a desire to do my part for the environment.

Because my utility offers net metering I couldn't find any compelling reasons to get the powerwalls. There are cheaper ways to maintain power during an outage, if I ever felt the need for it.

 

[willow_hiller]

If you're in Prince George's County, we've got a solar property tax credit up to $5,000: https://www.princegeorgescountymd.g...Alternative-Energy-Tax-Credit-Application-PDF

The waiting list is long (I just submitted my application, and it could take as long as 2025 before the tax credit applies), but if I factor in the Federal Tax Credit, the MEA state grant, and the county property tax credit, it brings my ROI from 10 years down to just under 4.

 

[h2ofun]

Thanks for the help everyone. I've decided to go solar with an 8.16 kw setup for the increased home value, the immeasurable but helpful roof shading, and a desire to do my part for the environment.

Because my utility offers net metering I couldn't find any compelling reasons to get the powerwalls. There are cheaper ways to maintain power during an outage, if I ever felt the need for it.

Totally makes sense to me

 

[garrett5688]

We went through ROI estimates when considering going solar last year - with cheap electricity rates in Texas (at the time, we were paying $.11/KWh).

Based on our initial it looked like break-even was 18-20 years out - a very, very long time!

When our utility notified us they were planning to increase our electric rate by 30% the next year, that reminded us to factor inflation into the projected long term energy costs. When we factored in the projected 2020 electricity rate and then added 3% annual inflation, that brought us down to 11 years for break-even.

Since we live in an area subject to hurricanes - part of the reason we installed our 15.4 KW of solar and 4 PowerWalls was to provide backup power for multiple days during a post-hurricane power outage. If we subtracted out the cost of a whole-home generator, that reduced the break-even down to 9 years.

After running our system for 5 months, our current electric plan (we were able to get a 6 month plan at $.09/KWh) was up for renewal. Based on the actual solar/grid usage using a combination of smart meter data and data from the Tesla app, we projected costs under various electricity plans and determined the best plan for us was a Free Nights plan, providing us free electricity from 9PM to 9AM and paying $.20/KWh between 9AM to 9PM. By using Time-Based Control for our PowerWalls, the system is configured to use solar and PowerWall power as much as possible during the daytime - and we've pushed some usage (pool pumps, EV charging) to night time. The combination has reduced our electricity bill even further, which could shorten our ROI by an additional year or two...

When we made the commitment to go to solar - we knew this would have a large up front cost and take years to make financial sense. Went through a similar total lifetime cost projection for my first Tesla (2012 S P85) which similarly showed a large up front cost, but if I kept the S for close to 100K miles, it would end up costing less than a luxury ICE.

We decided it was worth the longer ROI - and plan to stay in our house for at least 10 years after installing solar - so we should break even by the time we sell the house.

As for how much you'll get for solar in resale price - in the short term, we're not counting on seeing any more than getting credit for installing the equivalent of a whole-home generator ($15-20K). Our realtor advised us to expect quite a few prospective buyers to be reluctant to purchase a home with solar, since there are so few homes with solar in our area so far - and the buyers are concerned about increased maintenance and complexity.

But, we expect that attitude to change long before we sell our house. After we installed our solar, we've seen quite a few installations done in our community - and at some point, solar and battery storage will become a huge positive on home resale values...

And... it's great to see the much lower electric bills each month! Even though our system was sized to provide about 50% of our annual power consumption - using the Free Nights plan, through the first 7 days of November, we used only $.32 of electricity!!!

What are your settings in the Tesla app for your free nights plan? Planning to follow the same route, and want to make sure that solar+PW are maximized during day, and grid at night. And also want to minimize (ideally none) grid export since these free night plans aren’t net metering.

 

[cartwright]

When we installed solar one of my motivations was to be able to use electricity without having to think about being "wasteful". I installed a bigger system than necessary to account for adding a Tesla (did that a year later) but we still generate enough to cover the power bill. Due to time of use we use more than we generate but still have a negative bill. It is nice to not have to second guess turning on the AC.

So when doing ROI calcs, I estimated my desired use as opposed to my current use.