Person-Hours vs. Time-It-Takes in Solar Estimating - PVBid
Aug 25

Person-Hours vs. Time-It-Takes in Solar Estimating

How much time does it take?  Often the question an estimator finds themselves pondering.  There is a whole world wrapped into that question.  So today, we are going to unpack that.  I actually pointed to this topic a little in my last solar estimating conversation about Cost Codes.  That set of articles is worth a read.

So, how much time does it take to install a post?  A simple thing to determine: go out on a roof while a crew is installing those posts and time the installation.  But wait, is there more?  Questions come up, mostly around how you are tracking your information.  

  • When you are using this “post install” time, are you using it per post in your bids?  
  • Does the number need to include the time to move between post installs?
  • How are you accounting for setup time?  
  • All of this is to say, you need to dial in exactly what number you need.  

These are all questions that are easy to resolve too.  I’d tackle this solar estimating question by timing how long it takes my team to install all the posts on a roof and then divide that out by the number of posts.

And now we step into one of those gotcha’s.  Did you multiply it by the number of people involved in that install?  Because that’s the subtle difference between time-it-takes and person-hours.  It might take 5 minutes to install a post, but if it takes two people, then the person-minutes is 10.  If I have four people installing on one roof and each pair are installing in parallel, then the timing should be multiplied by 4.

The other gotcha, which is only kind of a catch, revolves around individual install times vs team install times.  I’ve found in about half the things that are installed a single person vs. a team take about the same number of person-hours.  Why is that?  Well, you have to account for the times when one person is working and the other person can’t.  Those moments when only one drill can be driving the one lag that needs to be installed.  

person-hoursThen there are those tasks when a team can install so much faster than an individual.  The old tilt-up kits are a great example.  One person holding the racking in place (because it likes to fall down) while the other installs the module goes so much faster than one person trying to make it all happen.

I like to log everything in person-hours and then divide by the crew size.  The result gives me crew-hours which is useful for my solar estimating practices.  I can also divide total person-hours by the crew-hours-per-day to get total number of days.  You can extrapolate a lot out of general person-hours.  And labor makes up such a huge portion of the work for solar installations that tracking it in this kind of way can give you remarkable accuracy.  

Unless you have figured out a way that is more useful.  Have you?  Leave a comment below if you have.  Let me know what you think.

And come visit me at Solar Power International!  That’s September 12th through 15th.  We have a booth in Startup Alley, hosted by the SunShot initiative and populated by SunShot awardees.

About The Author

With over a decade of experience, Connor English has watched and experienced the solar industry change and shift in dramatic ways. He has worked on PV systems from the ground up - selling, designing, building, engineering, and costing. With exposure to 100+ different company estimating methodologies, Connor has become a recognized expert in solar estimating.

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