California Solar Requirments

Adamjamma

Senior Member
It was announced, world wide , with a few other countries wondering about requiring similar. Jamaica made an official response that they will watch the developments in California and see what occurs in regards to firefighter concerns, utility concerns over covering the amounts of power possible from the houses, and other things so they do not expect to follow suit for at least ten years, in order to make sure such a policy is safe.
 

wwhitney

Senior Member
Location
Berkeley, CA
Here's my understanding:

The California Energy Code provides a prescriptive compliance option for new construction. There is also a computational compliance option, in which you have to show using approved software that your building will perform as least as well as a similar building built to the minimal prescriptive standard. In practice, most people use the computational compliance approach, as the prescriptive option includes a few things that are trouble. [E.g. it is easier to use a higher efficiency water heater than it is to deal with the exterior foam insulation required for prescriptive wall performance.]

Heretofore, the prescriptive design hasn't required any PV, but I believe that you could choose to install solar and get some credit for it in under the computational approach. The change for the 2019 Energy Code, going into effect at the beginning of 2020, is that the prescriptive design will now include some PV. So you can still in theory use the computational approach and skip the PV, but the bar has been set lower and it may be difficult in practice to meet the new requirements without PV. I'm not clear on just how much PV is called for in the prescriptive design, so I'm not sure how big an impact it will be.

Cheers, Wayne
 

wwhitney

Senior Member
Location
Berkeley, CA
OK, I took a quick look at what I believe is the latest draft of the 2019 CEC. The prescriptive requirement for PV is very significant, in my climate zone the prescriptive size for a single family residence is given by:

Minimum DC Watts = 1120 W + 0.628 W * (conditioned square footage)

There are exceptions for insufficient unshaded roof area, a central PV system for a multiple unit development, etc. And with the computational compliance approach, you can still reduce the size of the PV by making improvements elsewhere in the energy budget.

Cheers, Wayne
 

gadfly56

Senior Member
Location
New Jersey
OK, I took a quick look at what I believe is the latest draft of the 2019 CEC. The prescriptive requirement for PV is very significant, in my climate zone the prescriptive size for a single family residence is given by:

Minimum DC Watts = 1120 W + 0.628 W * (conditioned square footage)

There are exceptions for insufficient unshaded roof area, a central PV system for a multiple unit development, etc. And with the computational compliance approach, you can still reduce the size of the PV by making improvements elsewhere in the energy budget.

Cheers, Wayne
It will be interesting to see what approach the tract housing people take. That is, if they decide to continue building tract housing at that point.:eek:hmy:
 

jaggedben

Senior Member
OK, I took a quick look at what I believe is the latest draft of the 2019 CEC. The prescriptive requirement for PV is very significant, in my climate zone the prescriptive size for a single family residence is given by:

Minimum DC Watts = 1120 W + 0.628 W * (conditioned square footage)

There are exceptions for insufficient unshaded roof area, a central PV system for a multiple unit development, etc. And with the computational compliance approach, you can still reduce the size of the PV by making improvements elsewhere in the energy budget.

Cheers, Wayne
First of all, thank you for this info. So far I've only gathered some notes for further research on this subject. Can you point to particular energy code sections to back this up?

Perhaps your 'very significant' comment lacks some context needed to understand what you mean, but for a 2000sqft home that would be a 2376W system which is the about the minimum size my company would sell. (8 @ 300W panels, for example) So at least in that sense it doesn't seem 'very significant'.
 

wwhitney

Senior Member
Location
Berkeley, CA
First of all, thank you for this info. So far I've only gathered some notes for further research on this subject. Can you point to particular energy code sections to back this up?
I believe this webpage has the latest draft (the adopted draft?) of the 2019 Energy Code, but I haven't studied the adoption process to be certain of that.

https://www.energy.ca.gov/title24/2019standards/rulemaking/documents/2018-05-09_hearing/2019_Revised_EnergyCode.php

Section 150.1(c) has the prescriptive residential requirements, see 150.1(c)(14) for the PV requirements.

Perhaps your 'very significant' comment lacks some context needed to understand what you mean, but for a 2000sqft home that would be a 2376W system which is the about the minimum size my company would sell. (8 @ 300W panels, for example) So at least in that sense it doesn't seem 'very significant'.
What I meant was that the requirement seems to me large enough that it would be very difficult to comply under the performance based option (the computational option) with absolutely no PV and just making up the difference elsewhere in the energy budget. Although I haven't played around with the 2019 compliance software yet to verify that.

So in that sense it is a "real" requirement for PV. This contrasts with the 2016 prescriptive requirement for wall assemblies to have a U-factor of not more than 0.051, which would mean using, e.g., 2x6 walls with R-19 fiberglass and R-5 continuous insulation (typically on the exterior). Exterior continuous insulation can complicate a number of other details, so I believe many builders just skipped the continuous insulation and made up the difference elsewhere in the energy budget.

Cheers, Wayne
 
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