If you’re on SoCal Edison - switching to Time of Use plans really helps the electric bill I’m told (from people who have electric cars that I know). I’m on TOU plans myself but I don’t have electric cars yet. Not sure if LADWP has such a thing (I see you’re in LA).
If you have a PowerWall/battery storage then there are other fun options on TOU tariffs: charge your batter overnight and save on expensive daytime energy
Using a PowerWall to charge a Tesla seems a bit questionable for me, right now anyways. First of all, a PowerWall is 13.5kw, a fraction of a Tesla’s battery capacity. It’s continuous discharge rate is 5kw, half of the normal house charger (7.6-9.6kw depending on the model)... while the V3 supercharger is 250kw. The discharge is additive, therefore if you have 2 PowerWalls you cloud theoretically charge at 10kw. Otherwise I suppose you could supplement with grid power.
To charge a Tesla with battery power efficiently and with reasonable range, Tesla would have you buy 2 PowerWalls (though you would only be able to do a partial charge). With a PowerWall costing $6700 + $1,100 for additional hardware + at least $2000 for installation (potentially thousands more) you’re looking at ~$16,000 conservatively for 2.
It seems like an awfully expensive investment and considering the lifespan of the system being 10-15 (though there will be degradation obviously in the later years). Additionally, most people would be charging their vehicles at night when demand and electricity rates are lowest as it is... thus you’d only be reducing efficiency and wasting money. If in the future everyone has EV’s they charge at night, I suppose that could change.
Here in Mass the average electricity cost is ~$0.21 per kWh and the average American drives 1250 miles/month (15k miles/year). A Tesla Model S 75D is rated at 250 miles/charge and therefore costs ~$15.75 to charge up and would require 5 charges/month, therefore the cost to charge would be $78.75/month.
If I installed 2 Power walls at a conservative total cost of $16,000, the monthly cost would be $133/month over an estimated 10 year lifespan (I’ve read Tesla has offered 3% financing with $0 down for 10 years = $155/month). It’s important to note that 2x13.5kwh PowerWalls would at best charge 1/3 of a 75kwh Tesla at time before needing its own recharge, though at 15k miles/year or ~40miles/day this usually wouldn’t be a problem if you charge every day/night.
Home power storage for a car really only really makes sense if you have to charge during the day or have solar panels. Assuming 40 miles of driving equates to ~15kwh/day, to be on the safe side using Teslas specs suggest you’d need 7.5kW of their solar panels which in MA costs ~$14,000 with tax credits or ~$21,000 without (30% Federal tax credit expires at the end of 2019). You also have the option of leasing the same solar panel from Tesla for $100/month (plus $1500 removal fee).
If you paid $155/month for the 2 PowerWalls and leased the panels for $100/month that’s a cost of $250/month just charge your Tesla with stores solar... that’s a lot more than the $80/month just to charge your car with grid electricity- and this is considering an average electric cost nearly double the national average and not considering off-peak pricing which can be substantially less.
It only starts making more sense if you outright buy the solar panels ($40-60/month over 30 years) and live in area with expensive grid energy, however you also have to factor in battery replacement costs likely needed every ~10 years (presumably costs per kWh will continue decrease, though it’s believe much of the cost reduction have already been realized, barring substantial technological breakthroughs). On the other hand, it’s reasonable to assume grid power prices will likely continue to increase with increased demand (esp as EV adoption expands) and cheaper energy sources like fossil fuels + presumably nuclear are phased out. There is also the consideration of the opportunity cost of investing now vs later if solar + battery prices decrease.
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It seems you really have to be doing things on a large scale to have the economics work out... for most consumers it’s kind of a novelty or a very expensive alternative to a backup generator.
My dad is a partner in an investment firm that owns part of a company that makes grid battery energy storage systems, in fact a direct competitor to Tesla’s “PowerPack” (basically a much bigger commercial grid version of PowerWall). A lot of power companies and municipalities are getting into the buy low, sell high battery storage (as well as grid power regulation). Potentially in the future power companies using renewable energy and battery systems will achieve the concept discussed above except on the level of the grid instead of individual homes.
His company looked into home solutions however the market isn’t really there because the economics on a consumer level often don’t add up to be financially effective. Basically it might work if you personally have a very large solar array and a lot of money to invest upfront. Another problem is not all power companies will buy back power, or pay ridiculous low rates, and in some cases require new infrastructure to be built to accommodate accepting the power that is simply affordable to consumers. Many companies have tried the home storage market and failed. Tesla doesn’t sell many PowerWalls as it is and the product largely exists because Tesla is already making batteries and wants to sell as many as possible.
What I do think would be incredible for Tesla would be to allow their vehicles to be used as a home battery backup for power outages. Considering the craziness going on California’s power infrastructure, it would be very practical if people could use their Tesla essentially as a PowerWall backup system. The car could automatically shut off power once it reached a threshold determined by the distance to the nearest supercharger or preset by the owner.
