back to article Elon Musk pours more Kool-Aid into Powerwall

Elon Musk has responded to criticism of the specs of its Powerwall home battery, and says when it start shipping the system's output power will be doubled, without changing the price. Vegan seat covers weren't the only hot button Elon wanted to clear up at the company's annual shareholder meeting. “We actually took some of …

  1. spcb

    I wonder how many home users with existing solar power will have an inverter that can cope with 7kW peak? Not many in my area where the average installation is around 2-3kW.

    1. Ben Bonsall

      10kW inverters are common in the narrow boating community, well, among live aboards anyway... (often as a pair of 5kV with a manager and phase syncer)

      But then most of the continuous use stuff is 12 or 24v anyway, so the only big loads are oven, hob (if gas-free,) washer/dryer, microwave.

      Still, if you want a solar house, or a battery backup for storing economy 7, then time to convert as much as you can to 24v anyway. Do these things have a 24v take off, or only 240v?

      1. Proton Wrangler

        Output voltage

        Neither of those: the in - and out- are high voltage DC (~350V ?), presumably just at the battery string voltage. You have to have an inverter to get AC of any flavor.

        Most solar inverters will work with that current from the batteries, but combining it with solar PV is more difficult because the panel string voltage varies by nearly 50% depending on irradiance.

        SolarEdge is the company that has products best suited to integrating PowerWall, and they say a software upgrade for the inverter will make their products installed in the last 2 years compatible.

        pv-tech.org is an industry website that's pleasingly devoid of hype.

        http://storage.pv-tech.org/news/solaredge-customers-to-get-tesla-powerwall-batteries-within-six-months

    2. Weapon

      Personally I see no point in a 2-3kw installation. The best cost of return is probably about 7kw-12kw range. Based on statistics, in 2011 the average solar panel system was 5.7kw. There are no recent stats but based on what I have seen people are aiming for about 6.5kw - 8kw.

      1. AMBxx Silver badge
        Boffin

        Be interesting to read some use cases

        We live in rural Yorkshire. Our power has been known to go off, so we have a generator. Noisy, short running and thirsty, doesn't deliver good enough AC to run a PC, but good for keeping the freezer, freezer and central heating pump running. Gas hob for boiling the kettle.

        With one of these, we wouldn't be able to use the oven, but given the rarity of power outs, we could just use the hob.

        I can see a place for them - emergency backup power doubling as a store for solar power to reduce 'normal' consumption.

        Problem being, there are much cheaper ways of doing it using doing it with existing technology. Maybe he should focus on repackaging a cheaper alternative?

        1. Anonymous Coward
          Anonymous Coward

          Re: Be interesting to read some use cases

          "I can see a place for them - emergency backup power doubling as a store for solar power to reduce 'normal' consumption."

          It might reduce the owner's normal consumption, but that's just a way of milking more subsidy. In national terms using on site batteries would only reduce national consumption if you've got excess renewable capacity that has already displaced all marginal thermal plant.

          That, sadly, is DECC's misplaced ambition, and it will shove UK power costs back up to the eye watering levels that triggered all the political grandstanding in 2013-14.

      2. Joel 1

        @Weapon

        I'm assuming you are not UK based. In the UK, there are a number of factors which can make a smaller install preferable.

        The first issue is roof size - can you fit >4KWp on your roof? The majority of UK installations (by number) are <4KWp. Most houses won't fit >4KWp.

        Secondly, you can install up to 4KWp without having to ask the power company for approval - beyond 4KWp the power distribution company has to consider if the grid is appropriately sized to take the power (assuming you are grid-tied).

        Thirdly, the FIT in the UK reduces the rates for installations >4KWp. So for many people, 4KWp is the sweet spot for installation, assuming your roof can take it.

        Also consider that the best return is when you are substituting for your own electricity use. Most households have base loads below 1KWp <http://www.mpoweruk.com/electricity_demand.htm>, so it is only when you throw on the kettle, or electric oven etc that you get to use all your own power, even with a smaller system. And it would be rare to run a kettle all day...

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