{"id":7215,"date":"2026-03-21T15:07:20","date_gmt":"2026-03-21T15:07:20","guid":{"rendered":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/?page_id=7215"},"modified":"2026-03-22T12:14:32","modified_gmt":"2026-03-22T12:14:32","slug":"predbat","status":"publish","type":"page","link":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/?page_id=7215","title":{"rendered":"Predbat"},"content":{"rendered":"\n<p>There are a couple of limitations with the &#8216;native&#8217; behaviour of the Tesla PowerWall 3 inverter-and-battery system in my specific circumstances (dynamic electricity pricing and grid export limitations):<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The &#8216;smart charging&#8217; behaviour of the Intelligent Octopus Go EV charging tariff means that sometimes it schedules an EV charge slot outside the standard daily off-peak tariff time slot (23:30 &#8211; 05:30).\n<ul class=\"wp-block-list\">\n<li>When this happens, the import tariff applied to the monthly electricity bill is actually the off-peak tariff &#8211; despite it falling in a &#8216;peak&#8217; time slot.<\/li>\n\n\n\n<li>The PowerWall doesn&#8217;t know this, assumes any grid import will be at the &#8216;peak&#8217; rate, and tries to charge the EV from the PowerWall.<\/li>\n\n\n\n<li>The answer is to spot when Octopus have scheduled a peak-time charging slot and put the PowerWall into &#8216;Standby&#8217; mode for that half-hour (or potentially charge the PowerWall battery from the grid).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>On sunny days in Summer (when there&#8217;s no heating required so the electrical load is much lower than in Winter) it&#8217;s not sufficient to simply export to the grid when the solar PV is generating &#8211; the export limit imposed by the grid operator (5.5kW) means that the PowerWall battery receives a significant charge too, leaving it &#8216;too charged&#8217; by the next morning and resulting in curtailment of solar generation when consecutive days are quite sunny.\n<ul class=\"wp-block-list\">\n<li>The answer here is to:\n<ul class=\"wp-block-list\">\n<li>Predict how sunny it is going to be tomorrow &#8211; and how much electricity will be consumed on-site before and during tomorrow<\/li>\n\n\n\n<li>Force-export to the grid during the evening, to reduce the SoC of the PowerWall battery so it has enough &#8216;headroom&#8217; to accept all of tomorrows&#8217;s excess solar generation (and then export <em>that<\/em> tomorrow evening).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<p>The <a href=\"https:\/\/springfall2008.github.io\/batpred\/\" target=\"_blank\" rel=\"noreferrer noopener\">Predbat<\/a> add-on for Home Assistant does a lot of the work around Home Energy Management.<\/p>\n\n\n\n<p>The instructions for installing Predbat are fairly good, but a few surprises included:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>By default, the File Editor App limits access to the contents of the <code>config<\/code> directory &#8211; which stops it seeing the configuration files for add-ons like Predbat. The File Editor configuration needs to be adjusted, with &#8220;Enforce Basepath&#8221; set to False.<\/li>\n\n\n\n<li><\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>There are a couple of limitations with the &#8216;native&#8217; behaviour of the Tesla PowerWall 3 inverter-and-battery system in my specific circumstances (dynamic electricity pricing and grid export limitations): The Predbat add-on for Home Assistant does a lot of the work &hellip; <a href=\"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/?page_id=7215\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"parent":5370,"menu_order":2,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-7215","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=\/wp\/v2\/pages\/7215","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=7215"}],"version-history":[{"count":3,"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=\/wp\/v2\/pages\/7215\/revisions"}],"predecessor-version":[{"id":7225,"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=\/wp\/v2\/pages\/7215\/revisions\/7225"}],"up":[{"embeddable":true,"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=\/wp\/v2\/pages\/5370"}],"wp:attachment":[{"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=7215"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}