As a suburbanite who wants continuous power but not the noise and maintenance hassles of a generator, the Tesla home battery is something I’m excited about. The New York Times article on the announcement, however, omits one of two numbers that people would want to know: battery capacity. (The Tesla Web site says that it holds 10 kWh, which means it holds about 10X as much as a full-size car battery; a bunch of other media outlets managed to include this figure in their articles.) The Times article also omits to mention that the battery puts out DC voltage and that the price quoted does not include the inverter that would be required to turn the DC into AC.
Separately, why is this exciting if the capacity is about 10X that of a lead-acid car battery and the $3,500 price is roughly double the cost of 10 high-quality lead-acid car batteries? Will it last longer than deep-cycle lead-acid batteries? Is the amp-hour rating on a lead-acid battery, even a marine deep-cycle version, not realistic for “waiting for the sun” storage because if you keep drawing it all the way down you’ll need to buy a new one soon?
Personally I am kind of excited about this because it means that there will be a mass-market brand behind home battery backup.
Related:
- My November 2011 posting about using rooftop solar instead of a backup generator
- Airbus E-Fan (why leave the batteries on the ground?)
2¢ — If I were going to install a backup power system, I’d go with a natural gas (or propane) generator, http://goo.gl/vzP3iF. More than adequate to fully power a modern home for as long as the outage lasts. The weekly surveillance runs can be put on a timer. And the noise can be significantly reduced with a sound insulated doghouse or landscaping. Our server room was powered by a 60kw natural gas generator. Worked as designed, every time. 10kw-hr is not a lot. Our freak 2011 Halloween snow storm took out power for a week, in some places more than 2 weeks.
Tesla will probably sell a lot of Powerwalls as long as they don’t develop a history of shorting and burst into flames. Are they water proof? How hot do they get during a charge? What is cost of charge/discharge inverter?
If I lose power for more than a day I batten down the hatches to conserve heat and go to a hotel. Frozen pipes are my biggest concern. House will stay >32°F for 4/5 days depending on outside temp and wind.
I’m interested in the Honda EU series ultra-quiet generators; Yamaha has ones with a similar (low) noise level.
Not only do you have to look at the total capacity but at maximum wattage. This is 2.0 kW continuous, 3.3 kW peak. First of all, this means that you may only get 5 hours of backup, not enough to even make it thru one night. You really don’t need backup for 5 hours – in that amount of time your freezer won’t thaw and you won’t freeze. You really need backup in case of the catastrophic storm where you lose power for a day or two or more. In a bad storm, it can take up to a week and sometimes more to get power back.
Second, what do you want to back up? Is it just your computer and your phone chargers and some minimal lighting? This thing might work for that, but so would a good sized computer UPS plus a couple of LED lanterns. But do you want to run your refrigerators and freezers and your HVAC system? This is not even close to sufficient for that. There is not enough juice there even to start the compressor on your HVAC system or the blower on the gas furnace in winter.
For the same $3,500 you could have this 17 kw generator
http://www.amazon.com/Generac-5873-Air-Cooled-Generator-Compliant/dp/B003IT76DO/ref=sr_1_3?ie=UTF8&qid=1430497022&sr=8-3&keywords=backup+generator
which would allow you to run pretty much everything in your house as if there was no outage.
BTW, Tesla’s price is for the battery pack only and does not include the inverter, transfer switches, installation, etc.
Or else, when you lose power, you can drain your pipes (if it is winter – just shut the main inlet valve and open the taps in your basement laundry sink), check into a hotel and claim on your homeowners insurance for the contents of your fridge and your houseplants.
I already have a Tesla branded box in my garage as battery backup for four of the circuits in the house. (The refrigerator is on there, but I think I said I wouldn’t open it very often if the power was out.) I get everything I need, although no laundry.
I have solar that will charge it during the day. I am small footprint and everything is pretty low-draw. SolarCity said that I would be good indefinitely in the event of a power outage.
BTW, if you buy a Tesla (or other) electric vehicle, shouldn’t they provide you a way to tap into the vehicle batteries that you already own and are sitting in your garage? And if you own a Volt, you not only own the batteries but a generator already. And not some crappy air-cooled unit but a lovely quiet water cooled 4 cyl generator. And the vehicles all have charging ports – how hard would it be to make these 2 way devices?
I have a SolarCity panel on my roof (allegedly 3kW, but it seldom breaks past 2kW in not-so-sunny San Francisco). Tesla ran a pilot with SolarCity, and this unit should really be understood as a way to “bank” unused solar electricity in the day for use at night instead of selling it back to the utility at whatever piddling feed-in tariff they concede you. The savings are (full retail tariff – feed-in tariff) x electricity used from the battery.
I don’t know the exact values for my installation (it came with the house I bought less than a year ago), but given my electricity + gas bill is around $200/month, and assuming an optimistic 20% savings on the electric part, it would probably take at least a decade to pay for itself.
Lead acid batteries shouldn’t be discharged below about 70 to 80% or damage will occur to them. I believe that is not the case for the Tesla batteries.
In a car, the weight savings of lithium batteries are worth the extra cost. Batteries sitting in place at your house, not so much. It’ll be interesting to see how Tesla justifies this.
I remember reading about Priuses being used as generators during the Sand storm. You need one with a plug-in.
You need a 25KW genset to operate a typical fully-occupied 4 BR suburban house without power conservation measures (full lighting, AC-heat, washer/dryer, water heating and kitchen service.) A battery might allow a smaller powerplant to service outages or to delay firing up the generator during shorter outages.
Has GM considered marketing its Volt automotive powerplant as a stationary power technology ?
CHenry – since the Tesla system is only 3Kw, it barely makes a dent in what is needed if your really think 24Kw is needed. Most people are willing to forego things like drying clothes during a power outage, so you might get by with 10 to 20kW if you are willing to cut down to essentials, esp. if you have gas fired appliances.
For the numerate, a lifecycle analysis of Tesla’s powerwall system, from an environmentalists’ perspective. It concludes that the powerwall, unlike traditional PV and battery systems, might just barely be net carbon-neutral, instead of a net carbon-producer.
Please ignore my earlier post, it contained a non-working link.
I’m living on a boat, so I spend the sunnier half of the year off-the-grid, with a PV + genset + lead batteries mix.
If you want to maximize the number of MWh going through your deep cycle lead batteries over their lifespan, you shouldn’t empty them beyond 50%, so 10kWh of Li-ion is to be compared with 20kWh lead. 20kWh worth of high-end lead batteries would cost close to €10K.
The biggest difference is in the number of cycles. To take my personal example, my 10kWh lead battery bank will do 1000 cycles at 50% discharge, hence buffer a cumulated 5MWh, for €1300 VAT. It can go up to 6MWh with shallower discharges, but that’s still €0.20/kWh for storage, not counting production. This number is pessimistic, as a battery is considered wasted when it lost 20% of its capacity, but Tesla seems to be an order of magnitude cheaper.
(There are longer lasting lead batteries, which would yield a somewhat better amortized price; I’ve bet when buying that technical progress would make my batteries obsolete before they’re wasted, and Tesla seems to vindicate that bet)
What’s interesting is that with PV + battery + a cheap genset (that would run a couple of hours a year in emergencies or under extreme weather conditions), you can go off-the-grid for a couple thousands. That’s some pressure put on grid operators. Also, the utility-size PowerPack is probably much more disruptive, as it allows grid operators to store energy, whereas most of their job was to circumvent our inability to do so.
Also, when you start counting your kWh, you realize that there are many low hanging fruits in energy savings, and you can halve you electricity bill without significant comfort drawbacks. It’s just that you don’t bother at grid prices (here the flat rate is at 0.12€/kWh).
What I wonder is, have we got enough raw material on Earth, lithium and others, to build the couple billions PowerPacks that could handle the world’s power needs?
The Tesla battery system is innovative in ways that are useful for a vehicle…that is, something where you really don’t want to haul the equivalent in lead-acid batteries around with you all the time. Your house, however, probably has an acceleration curve that already really sucks, and so the extra weight of old-fashioned batteries that do the same power job cheaper wouldn’t be much of a problem.