A while back I posted a thread about how I was considering solar power for our house. After a -lot- of research, number crunching, etc I decided to pull the trigger back in January. After permits, approvals, and everything else involved the install finally went in April 4th. I got the following:
30 Tesla/Solar City solar panels rated at 325 watts per panel. 9.75 kilowatt maximum capacity.
1 Tesla Powerwall 2 13.5kw battery backup and accompanying hardware.
Ignore the hole in the wall. That was there when I moved in.
So after all this got installed it takes a while to get it up and running. The city inspector needs to sign off, which takes a week or so. Then you need to sign some docs with the utility company, who comes out and installs their own meter to measure how much your solar panel system generates. The whole process can take 6-8 weeks after the actual install, but I lucked out and the utility company installed their meter today, a little fewer than 3 weeks after the initial install.
Today was my first day of actually generating solar power. I turned the system on at about noon and I was able to generate 35.2 kwh during the remaining daylight hours. Now that it's nighttime the whole house is running on the Powerwall so we are still not using the grid. Surplus solar goes back into the utility company and stored as credit I can consume at a later date. Even though my electric use is a bit high I suspect that I'll be net positive between solar production, running on battery at night, and credit stored with the utility company.
Anyone else install solar? How was your experience? Good? Bad?
Byshop, thanks for the update. I remember the post leading to this -- nice to see an idea come to fruition!
I'm working towards home ownership, so I live vicariously through my friends in that regards. The few who have solar panels absolutely love them. We're in FL so, there's plenty of sun to help keep them in the positive.
I'll try to ask them more about their setup experience next time the topic comes up.
35.2 kwh in less than a day? Damn, I'm jealous. I'd love to be able to go off-grid but solar's not worth it yet this far north. :(
Half a day, since I didn't turn the system on for the first time until it was nearly noon. I don't know how much it'll generate on a good day yet. I was hoping to figure that out today, but this morning has been cloudy so output has been roughly halved. Still enough to run the house and charge the Powerwall, but not enough to also give back to the grid. I'll post back this week with what my real numbers are once I have them.
@shellcase86 said:
Byshop, thanks for the update. I remember the post leading to this -- nice to see an idea come to fruition!
I'm working towards home ownership, so I live vicariously through my friends in that regards. The few who have solar panels absolutely love them. We're in FL so, there's plenty of sun to help keep them in the positive.
I'll try to ask them more about their setup experience next time the topic comes up.
Yeah, no worries. I'm still playing with the settings and rate plans to figure out the best option, but ideally if you do this right one of two things will happen. Either you'll save money immediately because the financing for the system will cost less than the amount you were paying for the electricity you were buying (but there are a lot of factors that go into that) or even if you break even or pay a little more, that's money you're now paying towards paying down a home improvement as opposed to throwing away at the utility company.
Here are some screenshots from the app. This is the house during the day running a point of high load:
Here's normal load running off solar, charging the battery, and giving the extra back to the grid:
And here's running at night off of the battery:
With a single battery, the house ran on battery until about 2AM at which point it switched back to the grid (I have it set to keep some battery in reserve for power outages). This morning we consumed a little over 8KW from the grid before the sun came up enough for us to fully flip over, but we have back 9KW yesterday so even though we weren't completely off the grid we won't have to pay for that part. If I had a second battery we would have been completely off the grid, although with the way the credits work it wouldn't have saved any money.
I remember you're last thread Byshop on the Solar Panels. Did you have to install the panels yourself or somebody did it for you?
I like this thread, it makes me want to try out Solar panels myself. I'll have to see if my House insurance has anything for solar panels house.
I do have one question. How much power usage does your family use in the house?
Oh god no, the company does it for you. You gotta be a licensed contractor to do all that stuff. A lot of electrical work that needs permits, inspections, etc.
Regarding insurance, you probably don't need anything special on top of existing insurance unless you're already underinsured. Insurance companies put a buffer usually of about 20% on the dwelling and if the solar system is within that then there's no adjustment. Not sure if this is state or fed, but at least where I live if you get a system that's 10KW or greater you have to get some extra insurance because that's considered a "commercial" sized system, but stay under that and you're fine AFAIK. I've got 30 panels on my rook and I'm still under 10KW.
As for the number of KWs we use in a month...
I'm a bad example because I have a lot of tech in our house. Smart home automation for like everything, smart bulbs, literal HP servers, etc. We used to get nasty grams from the utility company telling us how we rate compared to our neighbors. Gas is crazy low because of a brand new, efficient furnace, but electricity was always 2-3 times more than other houses nearby. It's tricky because of our schedules, too. I work from home, and we've got two kids, so it's rare that there isn't someone in the house for more than a few hours at a time. I've gone through a lot of exercises to reduce consumption and managed to get us down to 1kw to 1.5kw per hour in a 3200 sqare foot home. .5 of that is my server room which has to stay running all the time, another .3-5 is "miscellaneous" and that the house just seems to consume at all times, and another .5 is the lights, tv, etc that we use when we are awake and home. Other homes would likely use less. It's 2pm now and today we've used 20KW so far. Only 8.3 of that has come from the grid so far, and we've sent 7.5 back so far to offset that usage. We have been 61% self-powered so far today and that number will increase as the day goes on, and what wasn't self-powered we get for free because of the surplus credit.
@horgen said:
Damn. Almost 10KW from those alone at peak is a lot.
Yeah, that's the ideal scenario which likely doesn't exist. So far the peak has been 7.5, but I haven't had the system running a full 24 hours on a sunny day yet. 8 of my panels face north, which cuts their efficiency. Tesla doesn't tell you how they calculate this stuff but I reverse engineered their math a bit based on multiple estimates. They estimate north facing panels as producing 70% of whatever number they use to calculate the output of south facing panels, so my revised max possible comes out to something more like 8.97kw. Today's been a bit cloudy but right now I'm pulling 7.5. 1.7 is going to the house and 5.8 is going to the grid for surplus credit.
It's still called a 9.75kw system because they measure it based on the literal absolute maximum the system can possibly generation, not what it's likely to generate. They reserve those numbers for their "guaranteed minimum output", where Tesla will actually pay you for KWs the system didn't generate if it underperformed in a given year.
41k roughly, which is not just the solar but includes the battery backup which was 10k of that or so. That sounds crazy but the way the economics of it are interesting. First of all, there's a federal rebate that gives you 30% back on what you spend, so the actual cost to me is under 29k. However, the way it works is I'm still liable for the full price up front or via financing, so my loan is for 41k over 10 years with a 3.99% APR. My monthly payment on the loan is about $300, but that's not based on the 41k loan amount, it's based on an assumed loan of 29k. The reason why is the loan company structures the payment based on the assumption that you'll pay back the 30% you get back in taxes to pay off your system. The loan reamortarizes after about 19 months, so if you spent the 30% rebate to pay down your principle then your monthly payment should stay at that level. If you didn't, your monthly payment goes back up to what it would be if you were paying off the full amount (in my case, around $450 a month). This might sound like a lot, but my electric bill is around $250-$350 each month, so instead of throwing money away on utilities I'm now spending money paying down a home improvement.
Also, between tax refund and bonus pay I plan on paying it off within a year or two at most.
41k roughly, which is not just the solar but includes the battery backup which was 10k of that or so. That sounds crazy but the way the economics of it are interesting. First of all, there's a federal rebate that gives you 30% back on what you spend, so the actual cost to me is under 29k. However, the way it works is I'm still liable for the full price up front or via financing, so my loan is for 41k over 10 years with a 3.99% APR. My monthly payment on the loan is about $300, but that's not based on the 41k loan amount, it's based on an assumed loan of 29k. The reason why is the loan company structures the payment based on the assumption that you'll pay back the 30% you get back in taxes to pay off your system. The loan reamortarizes after about 19 months, so if you spent the 30% rebate to pay down your principle then your monthly payment should stay at that level. If you didn't, your monthly payment goes back up to what it would be if you were paying off the full amount (in my case, around $450 a month). This might sound like a lot, but my electric bill is around $250-$350 each month, so instead of throwing money away on utilities I'm now spending money paying down a home improvement.
Also, between tax refund and bonus pay I plan on paying it off within a year or two at most.
Cool, seems it is worth the total cost and it might save you money in the long run, however the price of electricity is much cheaper in Iran, where I’m living right now – something near 0.03 $ per kWh-, so going off the grid still is not the right option for me
Cool, seems it is worth the total cost and it might save you money in the long run, however the price of electricity is much cheaper in Iran, where I’m living right now – something near 0.03 $ per kWh-, so going off the grid still is not the right option for me
Yeah, the ROI (Return on Investment) various considerably based on how much you pay for electricity. Where I live, I pay a flat rate of about 0.10 to 0.13 per kWh between winter and summer respectively. At that rate, it'll take over a decade to pay off the system so solar is less appealing here than places like California where the cost of electricity can be 2-3 times more than what I pay. California has peak demand and off-peak demand rates, where during the highest usage hours you get charged more (like 2pm to 8pm, for example) so you are encouraged to run your large appliances during off-peak hours. Cali's off-peak hours are often still more expensive than my regular flat rate, much less their on peak charges. If you live in a state like that, you can pay off a solar system like this in closer to 3-4 years.
But that's just one aspect of the economics of this. There are a couple other points that make the math interesting:
The Solar Panel system is a home improvement, so even if you're "out of pocket" on some of the cost of the system because you haven't fully earned it back on energy savings it increases the equity of the home for when you sell it.
This ROI calculation assumes that energy rates will not increase over the 10-15 year period you are calculating your ROI against, which is almost definitely not true. Every rate increase you see for the rest of the time that you own the home decreases the timeline in which you'll see your ROI.
That said, .03 per kWh is -really- cheap. If that's all you're paying then something like this may not make any financial sense.
Damn. Almost 10KW from those alone at peak is a lot.
New record this week of generating about 60kWh in a day. Not too shabby.
This is what it looks like while you're charging a Tesla, though:
The car draws 10-12 kW while charging, and charging takes hours depending on how much you've depleted the battery. The battery's capacity is 75kWh on my car, and I've got one the smaller battery cars. Current models go up to 100, and the new Roadster coming out is going to have a 200kWh battery.
@Byshop: 60 in a day is quite good. Did you get any estimates on average and possible peak production?
They gave me a projected monthly/annual average across multiple estimates/designs. Based on slicing and dicing the numbers from multiple estimates, I was able to reverse engineer some of the logic that goes into how Tesla estimates these things. Here's a spreadsheet I built comparing the estimates I was given before I pulled the trigger on getting solar:
The estimated annual output of the system that I ended up getting (the 9.75kWh system) is 13,441 kWhs per year. Now exactly how Tesla gets to that number I have no idea, because they are likely using secret sauce to figure out power consumption based on data like average weather patterns (my exact system in something like Seattle might generate half as much juice in a year). What I am able to figure out is what they estimate the relative efficiency of the panels with my south facing panels (south facing is considered ideal placement for getting the most amount of sunlight throughout the day) versus my north facing panels (considered decent but not ideal). Tesla estimates the north panels as being 70% as efficient as the south facing panels.
13,441 kWhs annually averages out to roughly 37kWhs per day, but that's a flat average not factoring in seasons (a bunch of 60kWh days I get in the spring/summer might be averaged out by a bunch of 10-20kWh days I get in autumn/winter months, for example). I have no idea what my real world output's going to be because at this point I don't even have a week's worth of real data, much less a month or year's worth. It's possible (and maybe even likely) that Tesla underestimates your projected output. That seems weird, but part of Tesla's whole deal is they guarantee that number, and if your solar system generates less than their projected amount in a year they actually -pay- you out for the difference at a pretty decent rate (close to what I actually pay like 10 cents per kWh) so they are incentivised to not overestimate system output.
I'm trying to build some real data analytics around this so I can view trends over long term. Especially since there are actually different ways you can configure the battery to behave throughout the day (when it prioritizes charging versus discharging, whether you pull from solar or the grid during daytime hours, based on energy costs, etc). The Powerwall itself has an exposed API on the local network, so I've written a data collector that polls it one per minute and submits the results to a Log Analytics instance in Azure which I'm planning on parsing in PowerBI, but Log Analytics has some pretty cool built in query language and charting capabilities natively.
There are some gaps in the data like that big sudden valley on the left side because I'm having a little bit of trouble with the Powerwall's wifi adapter. It keeps dropping off my wifi network and I have to forcibly reconnect it from time to time, and when it's offline my data collection probe fails. Until I can fix that network issue I can't collect reliable data long-term, so that's what I'll be working on next. Reception in the garage is poor so that might be an issue (my car occasionally sees similar issues, although for the Tesla the car's API is hosted by Tesla and not on the car itself so it's less of an issue). I've already purchased another access point for my Ubiquiti ecosystem but I haven't figured out where I'm going to put it yet.
Honestly 41K does not seem that bad for a major home improvement @Byshop, especially given the fact that this will save you significant money each year. But I am thinking in California home prices so...
My folks redid their kitchen and that cost them 25k, and it was a pretty good job.
Concerning home sale, does a solar system add value to your home? For example, that 25k investment my folks made added about 60k of eventual worth to their sale value down the road. I think if I bought a home and planned to live in it for some time, my priorities would go 1.) kitchen improvement, 2.) bathroom improvement, 3.) solar energy system, 4.) and then yard.
Honestly 41K does not seem that bad for a major home improvement @Byshop, especially given the fact that this will save you significant money each year. But I am thinking in California home prices so...
My folks redid their kitchen and that cost them 25k, and it was a pretty good job.
Concerning home sale, does a solar system add value to your home? For example, that 25k investment my folks made added about 60k of eventual worth to their sale value down the road. I think if I bought a home and planned to live in it for some time, my priorities would go 1.) kitchen improvement, 2.) bathroom improvement, 3.) solar energy system, 4.) and then yard.
Anyway, congratulations and good work!
Yes and no. 40k isn't a crazy amount to spend on a home that's worth 250k or more, but this one is different because unlike other modifications which might increase your equity, this one does that as well as actually generating money since excess sent to the grid is banked as credit against consumption.
@Byshop: Great job! Absolutely fantastic! You are doing your bit!!!
Thanks. My motives aren't entirely altruistic as I'm looking forward to a cheaper power bill but yeah. Based on data over the last 7 days (only five and a half of which were after the system was turned on) I've reduced my net energy consumption from the grid from 353 kWh (the actual amount my house has consumed over 7 days, which is pretty high) to 87 kWh, so a reduction of around 75%. This hasn't even been a consistently sunny week. I'll have a better idea in another couple days of what a full week of solar is like.
In my country solar panels are barely subsidized depending on the municipality you are in, so they are expensivvve. Also you have to pay taxes for delivering electricity to the grid. Which means that it takes probably like 10-15 years of using solar panels before it zeroes out. In Germany they have a much more generous system with less taxes. Solar panels are becoming popular there at a much higher pace. (As of 2019 I think 46 gigawatts of solar power in Germany. Which is enormous for such a small population relative to China(174 GW)/USA(64 GW).)
@Byshop: I have a 5KW system about 5 1/2 years old, the most the panels have collected in one day is 37KWH. In the past the Tesla wall was not value for money - what made it worthwhile to switch? Also, what size battery did you get?
In my country solar panels are barely subsidized depending on the municipality you are in, so they are expensivvve. Also you have to pay taxes for delivering electricity to the grid. Which means that it takes probably like 10-15 years of using solar panels before it zeroes out. In Germany they have a much more generous system with less taxes. Solar panels are becoming popular there at a much higher pace. (As of 2019 I think 46 gigawatts of solar power in Germany. Which is enormous for such a small population relative to China(174 GW)/USA(64 GW).)
Wow, yeah. Paying taxes on the juice you give to the grid is pretty lame. That would be incentive to get a bunch of batteries and stay off grid as much as possible.
@THUMPTABLE said:
@Byshop: I have a 5KW system about 5 1/2 years old, the most the panels have collected in one day is 37KWH.
In the past the Tesla wall was not value for money - what made it worthwhile to switch?
Also, what size battery did you get?
The rating that Tesla gives on their panels is that they'll generate about 70-80% of their rated capacity in ideal conditions. Your peak is more than half of mine on a system that's less than half the size so that seems pretty good.
A single Powerwall 2 is 13.5kWh. Two would have been enough to power my house for a day of low usage assuming no solar comes in. With solar I'd be completely off grid except on days with very little sun. Powerwall by itself probably isn't worth it but as an addendum to a solar install it's not bad. Plus it gets the 30% discount from federal taxes.
Log in to comment