Does anyone have a Tesla Powerwall (or another type of battery system)? - Page 1
Forum section: electronics / general

author: Halcyon
author_rank: Unknown
timestamp: June 21, 2017, 08:51:27 am
content: I've been strongly considering installing a battery system to supplement my 5 kW solar system on my home. During the week, most of my usage is in the evenings or at night. I'm on a net metering system. At the moment I'm getting 6.7c per kilowatt hour back from my energy supplier (soon to go up to 12c/kWh) but when the sun goes down, I'm buying it back for something like 23c/kWh. My household consumption averages about 20kWh per day. During autumn/winter, I generate about 6.7kWh per day in excess electricity which goes back into the grid.I've been getting a few quotes together for Panasonic, LG and Tesla Powerwall systems. So far, Tesla's offering looks quite good. They guarantee 13.5kWh of usable capacity (to 100% depth of discharge, which I'm guessing they are achieving by adding slightly more capacity to the system), the system is scalable (where as the Panasonic one isn't), they guarantee 70% capacity after 10 years with unlimited discharge/charge cycles (in a residential installation) and they offer the option of using it as a giant UPS for your house if the mains grid goes out.Does anyone have any thoughts, opinions or experiences they'd like to share?

author: kaz911
author_rank: Super Contributor
timestamp: June 21, 2017, 09:05:16 am
content: subscribingI'm interested in the opinions here as well.

author: Halcyon
author_rank: Unknown
timestamp: June 21, 2017, 09:26:02 am
content: Just in case anyone's interested, today I was quoted just under AUD$9000 for a 5.3kW Panasonic system which includes installation. This is the first quote I've got so far, I'll update this post as I get more information.A couple of the other guys at work are also in the same boat as me, we're all doing our homework and collaborating.Here is a little comparison table I've put together from what I've found out so far (obviously it doesn't go into any great detail and figures may vary):Tesla Powerwall 2Panasonic LJ-SK56AInitial Usable Capacity (kWh)13.55.3Max. Inverter Efficiency90%93%Output (kW; Peak/Cont.)7 / 5? / 2Warranty10 yrs; Unlimited cycles*10 yrs. @ 1 cycle per dayGuaranteed Energy Retention70% after 10 years60% after 10 yearsPower Back-up Option?YesYesScalable?Yes, up to 10 unitsNoDimensions (mm)1150mm x 755mm x 155mm1380mm x 966mm x 224mmWeight120kg136kgOperating Temperature Range-20°C - 50°C0°C - 40°CPrice (including install)**TBA~AUD$9000Since I'm in Australia, everything is 240VAC.* Unlimited cycle warranty only applies to solar self-consumption or backup supply. For all other applications, warranty covers up to 37.8 MWh of aggregate throughput.** Cost shown assumes you have a pre-existing and suitable PV system and inverter.Links to warranty documents:Panasonic LJ-SK56A,Tesla Powerwall 2

author: tszaboo
author_rank: Super Contributor
timestamp: June 21, 2017, 09:35:02 am
content: I believe the Powerwall 2 goes for something like 5000 USD + Tax + Zubehör. What I dont understand is: If you are on net metering, than why would this make sense? My parents (who live in a different country) are on net metering, so ever year, they read the consumption and production, they pay (or get back) the difference, and the pre-payment next year is based on that. Every year.How does this work in Australia?

author: VK5RC
author_rank: Unknown
timestamp: June 21, 2017, 09:35:49 am
content: Unfortunately nothing to add myself but interested ++Thanks.

author: Red Squirrel
author_rank: Super Contributor
timestamp: June 21, 2017, 09:37:07 am
content: I'd like to at some point. Though I'm a bit old school, I'd do a telecom setup with lead acid batteries. I feel they have less chance of exploding.Basically:Hydro feed -> Rectifiers -> batteries -> large redundant inverters -> main panelAdd solar to the mix too and only run rectifiers when voltage goes below say, 48.0 volts. Would float at 54 volts most of the time.All that would be really expensive though, so would need to figure out how fast it would pay for itself. The biggest cost on the power bill is not the usage, but the delivery and all the other fixed fees.How do the powerwalls work, do they have the power electronics built in to do what I described? The inverter would need to be big enough to run the whole house, unless you want to split up your panel and pick and choose circuits. Suppose that is a cheaper option as you can go with a smaller inverter, but it makes your electrical more complicated.

author: Halcyon
author_rank: Unknown
timestamp: June 21, 2017, 09:44:11 am
content: Quote from: Red Squirrel on June 21, 2017, 09:37:07 amMy very brief understanding is that the original Powerwall 1 didn't have a built-in inverter, you needed to already have one which was compatible with the Tesla gear or you needed to purchase one. The Powerwall 2 has a built-in inverter and charge management circuitry which will interface with your existing solar inverter and switchboard.

author: Halcyon
author_rank: Unknown
timestamp: June 21, 2017, 09:53:17 am
content: Quote from: NANDBlog on June 21, 2017, 09:35:02 amOur meters in Australia are read (and billed) every 90 days and we don't pre-pay our power consumption*. It makes sense because a large amount of the energy I generate during the day is "wasted" back into the grid, then when people get home of an afternoon/evening (when the solar is generating almost nothing), lights/air conditioning/electronics etc... go on and I'm paying the electricity company for the power we consume.If I can store the excess I don't use during the day when usage is minimal (consumed mostly by computers and the fridge), I can use what's stored in batteries at no cost at night.* There are some retailers which allow customers to pay a smaller amount each month based on an average of previous usage. It's designed to prevent "bill shock" for those who can't budget.

author: Jeroen3
author_rank: Super Contributor
timestamp: June 21, 2017, 10:02:26 am
content: So, a Tesla Powerwall provides 40 MWh of storage over it's full life, approximately. It will cost you, ~15k, including solar, that is ~35 to 40 cents per KWh? Quickly at the back of the napkin.Maybe even worse, on cloudy days it might not get a full charge.Looking at this it is very expensive energy.And, for the backup power function you'd need a mains breaker, correct?

author: tszaboo
author_rank: Super Contributor
timestamp: June 21, 2017, 10:05:14 am
content: If you have net metering, and it is 90 days, than I dont think it makes economically sense to install batteries. You basically just produce the energy during the day, and use it at night. Yes, in the summer (winter???) you generate more, but you would need to store that for more than 90 days. The network is the battery.

author: Halcyon
author_rank: Unknown
timestamp: June 21, 2017, 10:08:38 am
content: Quote from: Jeroen3 on June 21, 2017, 10:02:26 amBased on the original Powerwall 1 (which had approximately half the capacity), the system would pay for itself within the 10 year warranty period. This was based on a 4KW PV system + Powerwall available in January 2016 for under AUD$15,000 and the average solar generation in Sydney AU on a 4KW system is about 15.6kWh per day (averaged across an entire year). Most parts of Australia have higher generation (the highest being Alice Springs at about 20kWh per day).Quote from: Jeroen3 on June 21, 2017, 10:02:26 amNo idea how this works.

author: Halcyon
author_rank: Unknown
timestamp: June 21, 2017, 10:10:41 am
content: Quote from: NANDBlog on June 21, 2017, 10:05:14 am'The problem is, the network pays me (currently) 6.7 cents per kWh I export, then when I get home, I'm paying 24.3 cents per kWh to get it back. As of July this year, power prices are increasing among most retailers.Looking at my past power bill, I exported 599 kWh to the grid which earned me a $36.54 credit to my bill over 90 days.The network is a pretty expensive "battery" in my opinion.

author: tszaboo
author_rank: Super Contributor
timestamp: June 21, 2017, 10:20:22 am
content: Then it is not net metering. In net metering, first they calculate the difference between the production and consumption for the period, and you only get payed for the excess production (usually with reduced feed in tariffs), or pay for the excess consumption (normal price).So I'm going to assume that you have Power purchase agreement, not net metering.Anyway, a back of envelope calculation: You have 15 cent difference in pricing. You make some 600KWh excess in a quarter. That is 360 dollars in a year, so ROI is about 25 years.

author: Halcyon
author_rank: Unknown
timestamp: June 21, 2017, 10:27:17 am
content: Quote from: NANDBlog on June 21, 2017, 10:20:22 amWe're talking about the same system. I'm not sure how you're getting confused?The only other option is gross metering which is where everything you generate on your solar PV gets pumped back to the grid and you're paid a solar feed-in tariff for it. Years ago where I live, the feed-in tariff something like 40-60c/kWh. This is where gross metering made sense because you were exporting the power into the grid for more than you buy it back for (people with large enough systems actually had their electricity accounts in credit). They put an end to that pretty quickly after everyone started installing solar.The default option now is net metering (and has been for quite a while), you'd be bonkers to keep an old gross meter these days.Storage makes perfect sense if your feed-in tariff is significantly less than your import price. Yes you have to factor in the cost of the system over a period of time, but even with the old technology, if was quite easy to come out on top.

author: tszaboo
author_rank: Super Contributor
timestamp: June 21, 2017, 10:40:33 am
content: I'm sorry, but you are using the term "net metering" wrong. Maybe even the DSO uses it wrong. In net metering, if you export 10 KWh during the day, and buy back 10KWh during the night, you pay 0.

author: Halcyon
author_rank: Unknown
timestamp: June 21, 2017, 10:47:05 am
content: Quote from: NANDBlog on June 21, 2017, 10:40:33 amI don't think so. Here's some maths using my current rates:Export 10 kWh = 67c creditImport 10 kWh = $2.40 chargeImport - Export = $1.76 out of pocket.As you said earlier, you have to take into account the lower feed-in tariff. In this example, the proceeds from my export don't equal or outweigh my total outlay. This is by definition what the word "net" means.

author: tszaboo
author_rank: Super Contributor
timestamp: June 21, 2017, 10:51:45 am
content: You said net metering. If you pay for selling 10KWH and buying it back, then you dont have net metering. its called Power Purchase Agreements.https://en.wikipedia.org/wiki/Net_metering#ComparisonPlease read this, and understand it. You are just using the term "net metering" wrong. What you have is not net metering.

author: Halcyon
author_rank: Unknown
timestamp: June 21, 2017, 10:55:59 am
content: Quote from: NANDBlog on June 21, 2017, 10:51:45 amI'm not going to go back and forth with this. What I have in place is net metering, this is what it's known as in the industry and it's pretty universal. Rather than relying on Wikipedia, you can refer to any number of government and industry websites. The only other option is gross metering (which I don't have). You can go ahead and call it "silly sausage PV scheme" if you like, it doesn't change what it is. Anyway, moving on... this was not the point of this thread.

author: tszaboo
author_rank: Super Contributor
timestamp: June 21, 2017, 11:09:42 am
content: Quote from: Halcyon on June 21, 2017, 10:55:59 amThere is:Feed-in tariffNet meteringPower purchase agreementAll relates to how the electricity meter is connected. Net metering has one, bidirectional meter, with one number on it, which can be negative. You have two meters. Its not net metering. Anyway, it is obvious you dont plan to correct your wording. I know, it is confusing. So yeah, moving on. you saw my estimation with the 25 year ROI?

author: Halcyon
author_rank: Unknown
timestamp: June 21, 2017, 11:14:47 am
content: Quote from: NANDBlog on June 21, 2017, 11:09:42 amFor what it's worth I have a single meter, then again, I haven't checked it in about a month, a second one could have mysteriously appeared? Who knows?

author: Monittosan
author_rank: Regular Contributor
timestamp: June 21, 2017, 11:16:05 am
content: Any reason why you're not building your own powerwall?

author: Halcyon
author_rank: Unknown
timestamp: June 21, 2017, 11:20:22 am
content: Quote from: Monittosan on June 21, 2017, 11:16:05 amThis field of electronics isn't my area of expertise. Plus I'm not licenced to touch/work on anything at 240v.

author: tszaboo
author_rank: Super Contributor
timestamp: June 21, 2017, 11:39:52 am
content: Quote from: Halcyon on June 21, 2017, 11:14:47 amJust a simple question. If you have one meter, you produce 10 KWh during the day turns in one direction, and use it at night, turns in the other direction, it will show 0 the next day, right? So you would pay 0. But you claim, that you have a more elaborate payment scheme. I guess you have more than 1 meters then? Maybe it is not even called net metering.

author: Jeroen3
author_rank: Super Contributor
timestamp: June 21, 2017, 12:23:45 pm
content: "Net metering" with a reversing counter is only temporary. If they notice you have solar, they will issue you a new meter, with two counters.Based on "the old meter is out of calibration".Wikipediahas an excellent page on this,including image.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 21, 2017, 03:01:15 pm
content: One of my projects is a small version of the Powerwall, about 1kWh and designed to be portable with the capability to full charge in 1-2 hours. It uses a pair of Nissan Leaf battery modules along with a hacked server PSU. Would probably use an ESP32 as the network controller, currently prototyping with a Raspberry Pi 3 but that uses too much power for the standby state.Those who have some sort of battery system or even just an automation setup should take a look at Ohmconnect, which pays you to use less energy at specific times.

author: Halcyon
author_rank: Unknown
timestamp: June 22, 2017, 12:22:58 am
content: Quote from: NANDBlog on June 21, 2017, 11:39:52 amWe haven't used meters that "turn" for many years. Everything is electronic and readouts are via LCD display, Ethernet, RS232 and/ir IR. Everything is done in one single meter, including time-of-day billing (peak/off peak rates) if that's the type of plan you're on. These are also known as "smart meters".There is nothing elaborate about it, homes with PV here are connected to the grid and import/export is measured using a net metering scheme. That is, whatever you don't consume is exported back into the grid as excess. That is called "net metering". The payment in which we receive back from the energy retailer is known as a "solar feed-in tariff".There are no if's, but's or maybe's about it. Even if you look up the definition of the word "net" in a financial/accounting sense, you'd come to the same conclusion. The tariffmaybe equal to the import price (in some countries), but in the case of Australia, it's far less. You can still have a solar feed in tariff on a gross metering scheme, however these days, it makes no sense to do that. Don't confuse metering with tariffs or payment arrangements, they are two different things. At one stage, I wasn't getting a feed-in tariff at all because of a paperwork screw up, that didn't change the fact that I was still on a net metering system.Nothing personal, but I'm going to side with the electrical distributer, government and manufacturers on this one and trust that they are using the correct terminology.For your benefit, I've attached a photo of my meter/distribution box (sorry about the lighting).

author: Someone
author_rank: Super Contributor
timestamp: June 22, 2017, 02:05:55 am
content: Quote from: Halcyon on June 21, 2017, 10:08:38 amYou'll need to show your working for that, it doesnt sound like it could profit alone. Even with the poor tariff structure you have at the moment:Quote from: Halcyon on June 21, 2017, 10:47:05 amThe 50%/50% split is a reasonable assumption for the storage, so you'd need to have a 10 year system cost less than 1.76*356*10 = $6400Don't see the profit yet! You already said better tariffs are available to make it less attractive. Also the Panasonic quote at half the storage size is already costing more than this. You'll be betting on electricity prices (and the grids energy arbitrage ratio) increasing more rapidly than other investments. With all the blustering from the government about the energy sector I wouldn't be investing on such assumptions.

author: Monittosan
author_rank: Regular Contributor
timestamp: June 22, 2017, 02:56:42 am
content: Quote from: Halcyon on June 21, 2017, 11:20:22 amUpgrading to an inverter that supports a battery (hybrid compared to grid tied or purely off grid)and making your own lithium battery from used cells mite be another option if you have the time.Extra low voltage under 120volt DC doesn't require a licence to work on.

author: Brumby
author_rank: Unknown
timestamp: June 22, 2017, 03:13:06 am
content: Just to clarify one very obvious difference in how two people are using the term "net metering".One is using it on a "point in time" basis and the other is using it in reference to an extended period. Interestingly,both of these usages refer to a value determined by the net flow of electricity- it's just the time scales that differ ... and that difference is significant when it comes to the electricity bill.For the "point in time" approach, when the net flow of energy is out to the grid, this is credited to the household at one rate - and when the net flow of energy is coming in from the grid, it is charged at another rate. There is price differentiation between exporting to and importing from, the grid that changes with each and every change of the flow of electricity. This requires either a Smart meter or two meters to be installed.For the "extended period" approach, there is no interest in the instantaneous direction of energy flow, just a simple arithmetic difference between the kWH that flows out to the grid and the kWH that are drawn from it. Here, the price differentiation is only visited once - at the end of the billing period. This only requires a single meter - and if it is an old fashioned electromechanical induction meter, there is no need to even change it. This has got to be the cheapest implementation at the utility end of the exercise. All they need to do is allow for readings to go backwards in their billing system - in case the solar installation is a net energy exporter over the billing period.The difference in overall electricity pricing can be quite significant, as this post describes:Quote from: Halcyon on June 21, 2017, 10:47:05 am

author: Brumby
author_rank: Unknown
timestamp: June 22, 2017, 03:20:25 am
content: Quote from: Monittosan on June 22, 2017, 02:56:42 amMy understanding - and I admit I might be lacking here - is that if you have any device hard-wired to the mains, you must be properly licenced. I take this as not only including an inverter - but anything hard-wired to the inverter, such as a battery bank. The only way around this is to have your own system, electrically isolated from and independent of grid-connected mains.

author: Gregg
author_rank: Super Contributor
timestamp: June 22, 2017, 04:29:30 am
content: Here is a 24 volt string of C&D brand 1212 Amp Hour at 8 hour rate on a friend’s off grid system. I did all of the major wiring to the inverter and Pelton wheel. The Pelton wheel is connected to a brushless automotive style alternator that outputs 17 amps at 27 volts 24-7.A big resistor dumps the excess as heat to keep the powerhouse dry. The battery room is separated from the powerhouse with a fire wall. A 3500 watt inverter supplies all the AC power.

author: Red Squirrel
author_rank: Super Contributor
timestamp: June 22, 2017, 06:35:44 am
content: Quote from: Gregg on June 22, 2017, 04:29:30 amNice! Those telecom batteries are quite impressve. We have 4 strings here of 3800ah ones. For those curious each one of those is 2 volts. In telecom we use 48v so we'll have several strings of those, 24 per string and they float at 54v. You can make a metal tool disappear if you make it touch two terminals. (I would not recommend that)Has anyone tried running a washing machine or central A/C system off an inverter? If I wanted to put my whole house on battery I imagine those two loads would be the most challenging to power because of the startup draw.

author: Jeroen3
author_rank: Super Contributor
timestamp: June 22, 2017, 07:04:01 am
content: Modern washing machines use motor drives. They don't have a lot of inrush anymore.Central A/C I don't know, but the indoor units in the office also use drives.

author: tszaboo
author_rank: Super Contributor
timestamp: June 22, 2017, 12:23:56 pm
content: Quote from: Brumby on June 22, 2017, 03:13:06 amYes, exactly. The one I'm describing, the net metering is for extended time. When it is instantaneous, it is always "Power Purchase Agreement". I looked up "gross metering" since it is an unknown term, and only Australian websites come up? Anyway, I'm going to accept that it means something else on the other side of the planet, and I cannot force a country to say potato instead of potato.But then please accept, that net metering means something else for anyone outside Australia. Sorry, I got little personal, since I work for a company, installing smart metering for solar panels and green energy in general, and handling database for it, and such.

author: rstofer
author_rank: Super Contributor
timestamp: June 22, 2017, 03:16:10 pm
content: For PG&E (California), Net Metering means net at the end of a 12 month period. Throughout the period, the utility bills for a metering charge only (about $5/mo) and, at the end of the term, the net of generation and consumption is settled up.My 8.5 kW array was more than adequate to provide my annual consumption and that creates a problem since I buy the solar energy on a Power Purchase Agreement of $0.15/kWh. But PG&E only settles up at about $0.04 (IIRC) so I don't want to be a net supplier. In fact, the Public Utility Commission rules state that I can't be a net supplier.Still, it was nice to avoid the $0.36/kWh Tier 3 charges (consumption well above Lifeline). Having a battery car made it an even sweeter deal because I was driving for $0.03/mile.Alas, we moved and our roof isn't conducive to installing solar again. Bummer...At some point, the utilities are going to force Time Of Use billing and On Peak will go well into the evening. In this case, batteries might make sense. If you can just slide through until Off Peak things will be much cheaper. Or, get a system large enough to be able to stay off the grid entirely.The utilities hate solar and, in Hawaii, there is a 4 year wait to get permission to install solar (that has changed but probably not improved, see linked article below). This in a place that is all sunshine! The problem is the Tier rates. The lowest (Lifeline) tier is intended for the economically challenged and is subsidized by the higher tiers. It isn't until the upper tiers that the utility makes enough money to maintain their system and, by definition, solar eats away from the top tier down. It becomes increasing difficult to afford maintenance as people move out of these higher tiers.It's awkward:http://www.pbs.org/newshour/bb/switched-rooftop-solar-move-hawaii-long/

author: metrologist
author_rank: Super Contributor
timestamp: June 22, 2017, 03:45:22 pm
content: I was looking for where I read that solar battery technology still costs ~$0.15/kWh for the batteries alone. There are inefficiencies in the charge/discharge cycle, and in both the solar charge controller and inverter. In practice I think one never realizes the full potential of the battery due to less than ideal operation and mfg issues. Add on installation and maintenance costs and I think off-grid systems are a net loss or break even at best.I started experimenting with a small panel and have discovered that I cannot win anyway I try. I am now considering running DC devices directly from the panel to create air circulation and heat.

author: rstofer
author_rank: Super Contributor
timestamp: June 22, 2017, 06:19:45 pm
content: When the vast majority of your energy is bought at $0.35+/kWh, batteries may help. Given a sufficient sized array. In the end, all batteries do is allow a time shift between generation and consumption.There is also the possibility of building a cabin where electricity simply isn't available. A real off-grid application.

author: Gregg
author_rank: Super Contributor
timestamp: June 22, 2017, 06:31:23 pm
content: Quote from: Red Squirrel on June 22, 2017, 06:35:44 amMy friend does have a 20 year old washing machine that works fine with his inverter that isn't true sine wave as well as a refrigerator. Cold beer is #1 priority so when the refrigerator is full of food the spring that feeds the Pelton wheel is 40 degrees F and becomes the beer cooler. Hair dryers are strictly forbidden but the coffee maker is not.The flooded batteries are actually UPS batteries and were replaced under warranty because the post seals leak. My friend doesn't understand batteries so I do the maintenance for him. The battery terminals need to be cleaned every 3 to 4 months, but the price for the batteries was right.

author: metrologist
author_rank: Super Contributor
timestamp: June 22, 2017, 07:40:59 pm
content: Quote from: rstofer on June 22, 2017, 06:19:45 pmIn my area, there is tiered pricing:$0.20 to 10kWh/day$0.28 to 40kWh/day$0.40 over 40kWh/dayI think the pricing model provides incentive to use less energy, and I keep my average use to around 80% of baseline. I’m having a hard time justifying solar at all, especially given your earlier comments. I expect the power companies to change things to cut the legs off this option, if tariffs don’t do it…For the OP, this is how I would look at it, just taking a rough stab at it…Usage: 20kWh/dayCost: 23c/kWhProduction: 6.7kWh/dayReturn: 6.7c/kWh (soon to go up to 12c/kWh?)Net use is then 13.3kWh/day at a daily cost of $3.059.The pricing on the Tesla battery system I saw was $11k and I think to determine the value we need to take the difference of what electricity costs vs return, or 16.3c/kWh.Production is only 6.7kWh/day and if we assume 100% efficiency all around, then that presents a value of $1.0921/day. It would take over 27 years to make up the cost of the battery (but that battery is larger than can be fully charged). The cheaper battery system was listed at $9k and would take over 22 years to make up, and it is a little smaller than what could be charged.

author: tszaboo
author_rank: Super Contributor
timestamp: June 22, 2017, 08:28:51 pm
content: Quote from: Someone on June 22, 2017, 02:05:55 amI dont think it actually makes sense to be an early adapter for this kind of system, if you loose money (degradation of battery) with each charge. If electricity prices go up, you can install a battery system later. Prices are likely to drop, and reliability and number of charges are likely to go up in a future system. Imagine, they finally start mass producing aluminium-ion batteries, and prices are halved.

author: hendorog
author_rank: Super Contributor
timestamp: June 22, 2017, 08:44:48 pm
content: Tesla powerwall is too large, and therefore too expensive for what I need:I use spot price power which is expensive at peak times and cheap off-peak. It can be very expensive at peak time.Therefore need a small battery to cover the peak time usage only.The other issue with the Powerwall seems to be the additional costs pushing the price up.The local energy company Vector quoted about NZD 17K including all costs. Tesla's website says 10K, but excludes install, shipping, inspection and their tax calculation is obviously wrong (and they call it VAT instead of GST). Teslas 10K is already 1500 more than the equivalent USD price.

author: Halcyon
author_rank: Unknown
timestamp: June 22, 2017, 10:10:13 pm
content: From my figures, I've worked out that the Tesla Powerwall 2 (including cost of installation) will cost (over 10 years and taking into account 3% capacity decrease each year) about 23.18c/kWh which is roughly around the price of energy from the grid.The Panasonic LJ-SK56A is even more expensive to run at 52.71c/kWh.With those figures in mind, unless the price of battery technology drops, it doesn't seem all that worth while. I think investing money in more energy efficient appliances and air conditioning units with inverters will yield larger savings.

author: hendorog
author_rank: Super Contributor
timestamp: June 22, 2017, 11:15:25 pm
content: Maybe mentioned or already considered but you can use the free solar power by dumping it into things - instead of feeding it into the grid:e.g.Cool/heat the house - so it gets to the desired temp faster when you get home and you have less solar.Run the fridge/deep freezeHeat the spaHeat the pooletcMuch lower capital cost than batteries and so payback is faster.