{"id":4736,"date":"2015-05-21T14:49:08","date_gmt":"2015-05-21T05:19:08","guid":{"rendered":"http:\/\/www.solarquotes.com.au\/blog\/?p=4736"},"modified":"2023-04-10T08:01:47","modified_gmt":"2023-04-09T21:31:47","slug":"the-cheap-cheerful-way-to-add-a-powerwall-to-your-exisiting-solar-system","status":"publish","type":"post","link":"https:\/\/www.solarquotes.com.au\/blog\/the-cheap-cheerful-way-to-add-a-powerwall-to-your-exisiting-solar-system\/","title":{"rendered":"The cheap & cheerful way to add a Tesla Powerwall to your exisiting solar system?"},"content":{"rendered":"
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What might be the cheapest way to install a Tesla Powerwall + solar?<\/p><\/div>\n

Note:<\/strong> The Tesla Powerwall 1 was released after this post and required a separate Battery Inverter and the existing solar inverter. The Powerwall 1 has since been superseded by the Powerwall 2, which has an integrated Battery Inverter – and AC couples to a solar inverter.<\/p>\n

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[Note: This blog post is an educated guess on how the Tesla Powerwall might work based on stuff Elon Musk has\u00a0publicly\u00a0said and the press section of their website<\/a>. So bear that in mind if making any decisions based on this post. Tesla have released sketchy and often contradictory technical details about the Powerwall, so it is impossible to be sure how the thing will work or integrate into an existing system. I’ve tried asking Tesla US and Tesla Australia for clarification, but with no luck.]<\/em><\/p>\n

Since Tesla announced their low cost home battery, many solar installers have been looking for the cheapest way to integrate one\u00a0into your home’s electrical system.<\/p>\n

This has led to the emergence of a whole new category of residential\u00a0solar system, that\u00a0had never really been considered here in Australia before the Tesla announcement – the not-very-catchy “Hybrid Solar Without Backup” system.<\/p>\n

This is a system which, to save thousands of dollars on the install, removes the ability for the batteries to power your home if the grid goes down. The batteries are only used to store solar energy. They cannot be used in an outage.<\/p>\n

Why remove the backup function?<\/h3>\n

Because (at the moment) it is very expensive to implement this functionality. You need a special battery inverter that can work in ‘island mode’. Such inverters start at about $3,000. On top of that, you may need to modify the house wiring so that high powered appliances like ovens and air conditioners can’t be used in ‘island mode’ (as they could either overload the battery or empty it very quickly). \u00a0Things\u00a0can start to get very expensive.<\/p>\n

So\u00a0if you are happy to forgo protection from grid-outages, just how cheaply could you add a battery such as the Powerwall to your existing solar system?<\/p>\n

Adding a Tesla Powerwall: The cheap & cheerful way<\/h3>\n

Requirements:<\/strong>\u00a0Your\u00a0inverter is compatible with the Tesla Battery Management System (BMS) and has a spare DC input.<\/p>\n

If you have a spare input on your inverter then Tesla have said that you should\u00a0be able to plug the Powerwall’s output directly into your inverter. No extra inverter needed.
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\nUpdate:<\/strong> there are mutterings that the Tesla DC-DC converter is so smart that it does not need a spare input and it can go between the panels and the inverter. I don’t understand how this would work without messing up the MPPT optimisation on the panels. I asked Elon Musk to clarify how this would work via Twitter, but he did not reply \ud83d\ude41<\/em><\/p>\n

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@elonmusk<\/a> Can the Powerwall share a single inverter input with a solar array (without screwing the inverter’s MPPT optimisation) ?<\/p>\n

\u2014 Finn Peacock (@Solar_Quotes) June 15, 2015<\/a><\/p><\/blockquote>\n