<story><title>California Votes to Require Rooftop Solar Power on New Homes</title><url>https://www.bloomberg.com/news/articles/2018-05-09/california-votes-to-require-rooftop-solar-power-on-new-homes</url></story><parent_chain><item><author>alkonaut</author><text>Requiring specific technical solutions is rarely a good idea. For example mandating that all new cars have catalytic converters is a common but not very good requirement. The requirement should be formulated as a goal&amp;#x2F;limit, not a solution.&lt;p&gt;Having one solution required means you can’t innovate to find a cheaper or better solution to the same problem.&lt;p&gt;The answer in this context would be to require a total net power draw for the home. Adding a production unit just gives more room in the calculation and not having one might mean more expensive insulation or smaller windows are needed instead.</text></item></parent_chain><comment><author>litany</author><text>That is how title 24 has operated for years. They have two methods for compliance, prescriptive and engineered. The prescriptive method is they specify minimum Efficiency values for things like insulation, doors, windows, HVAC, water heater, etc and takes climate zone into consideration. The engineered gives you an annual energy budget and you just have to meet that in the model. So for instance you can have a house that doesn’t have insulation but with enough solar on the roof you can make up for it. The idea is prescriptive is to make it easier on owner builders and engineered is so that professional builders can optimize with market forces in consideration and designers can make trade offs like spending more money on efficiency in order to allow larger openings (doors and windows) as a percentage of total area.&lt;p&gt;This solar requirement has been a long time coming. I haven’t looked at the new standard, it’s called Title 24 2019 because it’s still under development but they might just pushing the energy budget low enough that solar is effectively required. Otherwise it may be required for prescriptive title 24 compliance. The article talks about square footage and 2kW minimum systems which to me sounds like the prescriptive  requirement.&lt;p&gt;Personally I’ve never been able to use prescriptive for design reasons but some contractors for sure do, and they don’t understand the concept of modeling.&lt;p&gt;So yeah, you can innovate all you want and CA set it up that way for years now.</text></comment>
<story><title>California Votes to Require Rooftop Solar Power on New Homes</title><url>https://www.bloomberg.com/news/articles/2018-05-09/california-votes-to-require-rooftop-solar-power-on-new-homes</url></story><parent_chain><item><author>alkonaut</author><text>Requiring specific technical solutions is rarely a good idea. For example mandating that all new cars have catalytic converters is a common but not very good requirement. The requirement should be formulated as a goal&amp;#x2F;limit, not a solution.&lt;p&gt;Having one solution required means you can’t innovate to find a cheaper or better solution to the same problem.&lt;p&gt;The answer in this context would be to require a total net power draw for the home. Adding a production unit just gives more room in the calculation and not having one might mean more expensive insulation or smaller windows are needed instead.</text></item></parent_chain><comment><author>forapurpose</author><text>&amp;gt; Requiring specific technical solutions is rarely a good idea. ... The requirement should be formulated as a goal&amp;#x2F;limit, not a solution.&lt;p&gt;While I instinctively agree, does anyone know of any research in this area?&lt;p&gt;I can speculate about possible downsides to legislating a performance specification rather than a solution: Giving people every possible option could result in people gaming the system, it could hamper investment because it creates uncertainty about what the future solution will be, or it could simply reduce transparency because the specification may be written to favor one solution anyway. That&amp;#x27;s just speculation, however; we need data and expertise.</text></comment>