I placed an order last week for a 4kwh system because 8 kwh is too large for us, at the time 4 is not enough. I got the email to upload pictures of my panel and meter, but the design email came through before I uploaded the pictures - weird. I have not accepted the design because I would like upsize my system to a 5 or 6. Do I do this now? Or, with who? My site inspection is tomorrow.
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Order In - When to change size?
- Thread starter whydontwe
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I would let them know you want to upsize right now and see if they want to cancel the inspection. My guess is they will not. The inspection will determine what you have now. They can complete the design with your upsized system and use the data from the existing.
Also, good idea to upsize. The rates are only going up as time goes on. Having more solar means you offset more and don't buy as much power from DWP. Bad for DWP, good for you.
Thanks, and will do right now. I am in SCE territory. I am going back and forth on the Powerall. We use about 1,000 kwh per month on average. Sometimes less and some months more. I think I need 6 kwh system.
The person doing the site inspection generally check your roof condition and panel capacity. I thought I could tell him system size and PW location but he just said I need to discuss it with my advisor. I think you want at least one PW so when you have outage your solar will still work for day time and get you through peak time when the sun is not shining. NEM in CA is not 1 for 1 so you need to figure that one yourself. Do yourself a favor and size your system with PVWatts, specifically place the panels on section of your roof to get a better estimate. Project Sunroof gave me a smaller system because it assumes I would use the west facing roof but I have several big pine trees on the west side so it is better to have east facing for me though ending up with a bigger system because of loss of an hour or so usable sunlight. PVWatts let you place your panels where it is practical to get a more realistic system estimate.
Yup, I just called my Project Advisor and she said the site inspection doesn't impact the changing the system size. She put in a new design review for 100% offset then I can down from there.
While you are sizing your system, I recommend that (as mentioned by others in this thread) you keep in mind that net metering in CA is not a 1:1 thing.
In plain terms, that means that, in general, you put in 1kWh of energy to the grid via net metering at off peak rates, and you pull 1kWh of energy from the grid at peak rates, you need to put in more than you take out to balance it out.
If off peak is 15 cents and peak is 45 cents (just to use round, made up numbers) for every kWh you pull from the grid during that 45 cent time, you will need to put in 3 of them to balance it out.
So, its not generally "enough" to think "I only need 90% of my usage" if the goal is to have a zero true up bill. Only you know what you consume between peak rates of 4-9 or whatever they end up getting changed to, but if I were you, I would recommend not sizing for what you think you will consume or consumed in the past. I would size for at least 110% of my past usage.
For one thing, people almost always use "more power" when they get solar. They set the thermostat lower in summer and higher in winter, they dont pay as much attention to conservation because "I have solar now", so they use more power and are surprised at the end of the true up period.
For another, because of the above net metering, you really want to consider when you used your power, not just how much, and not try to pin down the size to "90% of past usage looks good". Its not easy (or cheap) to add on later, while its relatively cheap to add on now.
In plain terms, that means that, in general, you put in 1kWh of energy to the grid via net metering at off peak rates, and you pull 1kWh of energy from the grid at peak rates, you need to put in more than you take out to balance it out.
If off peak is 15 cents and peak is 45 cents (just to use round, made up numbers) for every kWh you pull from the grid during that 45 cent time, you will need to put in 3 of them to balance it out.
So, its not generally "enough" to think "I only need 90% of my usage" if the goal is to have a zero true up bill. Only you know what you consume between peak rates of 4-9 or whatever they end up getting changed to, but if I were you, I would recommend not sizing for what you think you will consume or consumed in the past. I would size for at least 110% of my past usage.
For one thing, people almost always use "more power" when they get solar. They set the thermostat lower in summer and higher in winter, they dont pay as much attention to conservation because "I have solar now", so they use more power and are surprised at the end of the true up period.
For another, because of the above net metering, you really want to consider when you used your power, not just how much, and not try to pin down the size to "90% of past usage looks good". Its not easy (or cheap) to add on later, while its relatively cheap to add on now.
As others have said, the peak-rate and off-peak has price different. In general, 20-25% price different in my area in Norcal. You're solar produce most of the power during off-peak. Therefore you need to produce 20-25% in off-peak to offset the peak-rate usage. I would recommend at least getting 125% off your last year usage.
If you're telling me, you use 1000 kWh per month. It means you need 12000 kWh per year. You would need 15MWh production system.
Using PVWatts to get an estimate ball-park number. It's very important of where you placed the panel. Use google solar roof site to get an idea the location.
At the end, I couldn't justify the price of the power-wall with reasonable ROI. Tesla only gives 10 years warranty on the battery. It's almost impossible to get positive ROI in that time frame. I only could able to see the benefit during blackout, which depends on how much you're willing to pay for that insurance.
I'm holding off the PW until time-of-use become more aggressive in pricing, or when Tesla start using the new battery type. Then the warranty can extend to 20+ years. Or if rolling blackout become a significant problem. If that's purely from the electricity money saving point of view, PW doesn't make sense for me.
For the site inspection, Tesla only doing electrical panel, grounding inspection. The most important thing is inspection of the roof condition, like your shingle condition, and whether your rafter can support the additional load. That's not doable using picture, that's why they're doing site inspection.
For the placement of the panel, and the panel location. The site inspector doesn't care about it. The design will give you something. In my experience, the designer in Tesla only trying to stuff the panel onto the roof. They don't care much about the efficiency for the production, or any shading problem. That's where you will come in to give your opinion.
Never depends on Tesla designer to give you the best option. They're a fast-food chain, don't expects they will give you a custom burger. Therefore, you need to ask for it.
This is helpful, thanks.
I had to ask the Project Advisor to get the re-design going. I was never asked for an upsell to a larger system, but you would think that Tesla would try to do that, not sure??
I have never been subject to PSPS, fingers crossed. I live closer to the coast than the mountain areas. Like you, the payback on the PW is too long and I purely looking at all of this to save money on my energy bills.
I had to ask the Project Advisor to get the re-design going. I was never asked for an upsell to a larger system, but you would think that Tesla would try to do that, not sure??
I have never been subject to PSPS, fingers crossed. I live closer to the coast than the mountain areas. Like you, the payback on the PW is too long and I purely looking at all of this to save money on my energy bills.
Tesla doesn't give you an advise on the sizing of your system, or what is the best placement of the panel. They're a fast-food chain store for solar. They assume everyone placed the order want a solar. Their job is putting solar onto your roof, and passed inspection.
The only reason why they make sure your roof is in good shape is because they don't want to find out during installation, and cancel the work.
I would recommend your roof has 20 more years of life left. I have seem people asking Tesla to remove the panel, and put it back for new roof. The cost can be $5000. Then your ROI would be completely off.
I went with the most panels I could qualify for, and fit on my roof, and put largest inverter they had one. Everyone I talked
to once they got solar they could be cooler in the summer, and if like me with heat pumps, warmer in the winter. To add stuff
later is much more costly. With my battery install, I am over sizing everything since if I want to add more solar or batteries later, I am all ready for it. If not, the extra cost was minor.
Nice. Our inspection took about 4 hours and was very thorough. This was a partially because it was a SolarRoof, but also because they want to ensure that there is nothing defective that is going to cost a ton of time or money to remedy. Things like roof structure, faulty wiring, panels, etc. Once assured that everything looks more or less OK they will be able to incorporate those additional panels you want.
You should be able to ask the inspector for a look at the issues they found and how they think this will impact the project.
Please keep everyone appraised of your project's progress.
Also, I would recommend you to go with 150-175% of your usage. My math is 25% for peak and non-peak difference. 25-50% for EV or future usage. It's more costly to add later. Even Tesla will not add panel to the existing system, they will only put in a separate system. It means even you have more capacity in your inverter, they will put in a second inverter, a second breaker.
I believe that is do with the warranty problem. Adding panel into the existing system could make it very hard to separate the warranty.
I heard SolarRoof inspection is much more involve. They need to inspects all the vent, exhaust on your roof. If you have skylight, they need to check it as well. Also, they need to look at the gutter, and roof structure backing. (Some roof doesn't have plywood). It's like re-roofing.
Honestly, one thing which I have a lot of concern for solar roof is the cost of unrelated repair. Like your skylight, roof vent, and anything you need to touch the roof.
Because it's not a common roof, only Tesla know how to do it without voiding the warranty. It mean the cost can be unjustifiable.
What's your thought?
A solar roof is definitely a re-roof. It is going all the way down to the decking boards and building up from there. So if you have skip sheathing instead of solid OSB or strand decking boards you need to factor in the cost of that. But, at least in my city, any re-roof required OSB or strand decking boards, no more skip sheathing with gaps.
Part of our inspection was time to look at roof supports structure and decking. You would have to do a good portion of this for a standard solar panel installation to ensure the roof was in good enough shape and had an appropriate structure on which to screw in the panel mounts, run wiring, etc.
The remainder of the inspection time was spent checking out the wiring and how to route from the roof to the inverters, the best position for the inverters, and how to interconnect to the grid. Which are all things you need to get nailed down on any solar installation. The guy opened the various panel, did some load calculations, and even opened the main box while it was powered up. He had on this mask that looked like one you use in Arc welding and a leather protector that covered his neck, shoulders, and down to the middle of his chest.
Cost-wise it was about the same price as putting on a new tile roof, which we needed, and then solar on top of that. It was actually $1K less than the estimate we got from one of the very large multi-state companies for a tile roof plus solar. But, we are happy we went with Tesla. Especially since that company just went bankrupt, so the 25-year warranty they offered may be worthless.
The installation was done by crew members from both Tesla and a local roofing contractor. These local contractors are trained and certified by Tesla to conduct any future repairs.
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If I was this OP, I would be ordering the 8kW size if it fit on my roof, Production on that would likely be between 11-13 kW yearly depending. For me personally, it would be super annoying to do the effort of buying solar, and only cover 70-80% of my usage, meaning I would have a decent sized true up bill at the end of the year.
Having "too much solar" is a bit like having a car thats "too fast" or a TV thats "too large". The number of people who complain about a car being too fast, or a TV being too large is much (much much) smaller than people who complain about the opposite (car too slow, TV too small).
The Utility will only let you get 110-120% of your last year production anyway, and you likely need to say you are making a change to your electrical use to get them to allow it, but to me, its worth it.... especially if "there are no plans to move".
I would really consider that 8kW system if it fits.
I totally agree. You should get 8kW system if given your annual usage is 12kWh. Most of the utility would limit the system to 110-120%. I talked to Tesla about this. They told me, their interconnect department have communicate this before to the utility company. (I didn't ask further what that mean). The EA told me, they have seem people goes to 200% without any problem. FYI.
I do believe Tesla have done a lot of communicate to the City and Utility company before hand. Therefore, they could do something other solar installer cannot.
Tell the utility you want to add two electric cars and each car is about 4000 kWh so you can justify increased sizing ..
Usually they only allow 110-120% upsize as mentioned in tbe previous post.
I had a 16.32 kW order they reduced to 14.28 kW and I had to accept as the Utility won't approve.
I came to know about that I could contest by saying I am increasing the usage.
I will see how I got my future car into the plan will only have one electric car never both electric .
Usually they only allow 110-120% upsize as mentioned in tbe previous post.
I had a 16.32 kW order they reduced to 14.28 kW and I had to accept as the Utility won't approve.
I came to know about that I could contest by saying I am increasing the usage.
I will see how I got my future car into the plan will only have one electric car never both electric .
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