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Tesla Solar Panels & 2-3 Powerwall 2

Tesla Solar Panels & 2-3 Powerwall 2

Frist off, we live in Las Vegas with very hot summers and a lot of sun. So we are buying a brand new home and moving in hopefully in about 2 weeks. It is a 3867 sq ft. 2 story home with energy efficient appliances, etc. In addition we will be installing Ecobee thermostats, and other energy efficient devices to try to bring energy consumption down. We currently are in a 2306 sq ft. single story home (11 ft ceiling howeve in main area) that was built in 2000. Our energy consumption at our current home was averaging 30-35 kWh in the winter months and about 140 kwh/day in the summer months. We pay $.11/kwh for power with NV energy and then roughly $25 in basic service charges. So in the winter we average around $120-150/mo bill and the summer was approaching $500/mo.

With that being said, we want to get solar installed ASAP once we get in the new home. I know they like to use our last 12 months usage to determine size of the system, but as I said, we want to get it installed now. Since we are coming from a smaller home (but less efficient) and going to a bigger home, can we use the usage from our current single story home for the last 12 months?

Based on our current usage at this house, I think we need at least a 12kWh system to even get close to powering our home off the grid as much as possible. Do you think we can achieve 100% off grid even in the summer? How expensive is a 12 kWh system with Tesla to install? And then we want to get at least 2, if not 3 power walls installed to help keep us off the grid. I read somewhere that to calculate what we need, you take the area you live in (which that number is 2100), multiply that by .78 (loss of power through the lines, etc.), and then multiply that by the size of system. So if that is true, we are looking at 19656kwh produced annually with a 12kWh system. That will be enough for the winter months but not the summer months by my calculations. But I find it hard to believe that a 12kWh system can't power the home with the amount of sun and heat we get here in Las Vegas.

Oh, and we currently own a Toyota Prius Prime (6kWh battery) which we charge daily. We will probably be switching to the peak/off use power charge plan from NV energy once the solar is installed, so that the peak times we use nothing from the grid and then off peak we use some grid if we have to (which is only like $.04/kwh then). We have our reservation in for a Tesla Model 3 which will replace our Prius Prime whenever we get that (probably spring 2019), so it needs to be able to charge that as well.

Any suggestions, help, etc? would be appreciated. Like I said, we move in roughly 2 weeks and then want to get the process started in designing this and installing. We'd like to go with Tesla for the panels, Powerwalls, and installation. I'm guessing we are looking at roughly $50,000 for a 12kwh system with 1-2 powerwalls, but maybe Im off. Also, what financing do they offer? Thanks!

coolgj | 11 February 2018

You posted the same question on the other Tesla forum.

No one can tell you with out metrics. Have a solar install come out to the site and use one of your neighbor houses to give you a good idea of what you will need but it still will be only an estimate until you move In and start using electricity.

Also heat is actually bad for power production for the panels and inverters. You will actually produce less when it gets too hot. The panels and inverters will go into Thermal derailing. So sun good... To hot bad...

gballant4570 | 18 March 2018

Those summer months will likely require 15kw+ system to completely supply your need from what I am figuring for my needs, based on energy use. That statement is not based on experience, but on the research I'm doing trying to figure the size of the solar system I'll need. I am an electric hog, and figure I would like to get a 20kw system, especially when I start charging my car. I won't be getting as good sun exposure as you will, in MD....

gballant4570 | 18 March 2018

And you'll need 3 Powerwalls along with the solar.

gballant4570 | 18 March 2018

It'll be around 50k after the tax incentives, from what I'm seeing