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Optimising system size from 30min interval consumption data, available area, etc


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Hello everyone,

I'd like to talk about optimising solar pv system sizes for commercial scale projects.

When there is 30min interval consumption data, and information on constraints such as; available area and export limits - planning the right balance between system size and financial payback/ROI can be a slow and iterative process. The way I see optimising solar pv system sizes for commercial scale projects is by making simulation, after simulation, after simulation of different system sizes in an effort to arrive at the golden system size.

I was wondering if there are any methods via PVSol, or external to PVSol, that can speed up the process of arriving at the golden system size?

I guess this begs to ask what makes a golden system size? In this case, the projects are commercial financially-single-minded projects, I would suggest optimal payback/ROI would be the measure...

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  • 9 months later...
  • 11 months later...

Updates to this would be appreciated.


As mentioned, multiple simulations are required to find the sweet spot between system size and financial payback/ROI.  Is there an easy way to do this in PVSOL, or if not easy, what is the recommended steps to ensure success.


Maybe there is a better way external to PVSOL?


Thanks for your help with this.

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Is this something that is likeley to be answered anytime soon?  I ask because we are nearing the end of our trial..


We have got to grips with the software we think, but knowing how to fundimentally size solar PV arrays along with their batteries using PV SOL is still witchcraft.


If it helps you (I'm sure it would help others too using PV SOL), I'm happy to detail a current job we are modelling here so the process can be documented.  NOT how to use the software, but how to get the right 'balance between system size and financial payback/ROI'.


Looking forward to hearing from you soon.

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Hi Martin,


Thanks for the reply.  To be honest we don't.  We give a best guess but are normally lead by the client who comes to us to fill their roof with solar panels or to compete costwise with a similar design and cost they already have.


We are looking to actively change this for our clients to ensure their best ROI, and not to just line our pockets with the biggest array we can install.


We have a sizeable opportunity that is lead by investors, to size, install and maintain commercial solar PV systems along with battery storage where required.  We want our advice to be the best it can be in regards to ROI and have a sound arguement if our recommendations are questioned.


How best to proceed to ensure Valentin's expertise and 25 years in the market helps us to perfect the ROI process for our clients?



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Hi RaW,

thank you for the reply. I am sorry, but I don't understand that sentence:

14 minutes ago, RaW said:

Would me detailing an up and coming job here so we can discuss it in more detail help to iron out a best ROI process?

Do you mean you would present an upcoming job here so that we can discuss the best solution for the customer here? That would be great, I guess!

Also, I doubt that pure ROI can be a suitable target for an optimization process. The ROI will always be high if your investment is relatively small, for a small PV installation that produces so little energy that everything can directly be used to cover the loads. Say you have a consumption on site of 25000 kWh and you install a 1kWp PV system for around 1300 €, your ROI will be extraordinary (in percent), but the cash balance in € will be negligible.

Kind regards,


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Hi Martin,

I'll get some information together and post it here for some feedback and discussion..

I fully understand your point in regards to a tiny system on a large load.  I'm talking more about finding the drop off point where increasing the array size doesn't make sense costwise (even longterm) and finding the sweet spot for investment cost over energy cost savings.

I'll detail an example energy usage scenario here soon and fill the available roof space with soalr PV panels and hopefully raise some feedback.

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So, here is the most basic of data to get the ball rolling.  This is the type of enquiry we are getting more and more of. 

Although there are questions that we ask to expand upon their request (planned growth of business, funded or CapEx, etc.) if we can go through the process to find the sweet spot with the information we have, that would be great.


Commercial property in the Midlands - UK:

 - Energy usage attached (3 phase, NOT half hourly, showing day/night usage)

 - Roof space for maximum 544 panels, shade free


Client is asking for designs and costs for the appropriate array size that will give him the best energy savings balanced with the cost of installation.

They would like:

 - 1 x design of solar PV array

 - 1 x design solar PV array and battery


Currently, for current stock and availabilty reasons we are modelling using:

DMEGC Solar panels - DM410M10-B54HBB

Solax T-BAT-SYS-HV-5.8T58 Batteries

Solax X3-Hybrid-G4 Inverters

Presume £700 per kW install costs





Edited by RaW
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To reignite the discussion, how best to proceed to advise the client on the best ROI for them using the information we have only?

Based on the information given, what is the sweet spot for them (between 0 - 544 panels) investment-wise (@£700 per kW)?

Where would this sweetspot be if we were to introduce batteries into the equation?

I know, as a company, you have over 25 years experience in this field modelling solar PV arrays for commercial clients, so thank you in advance for your insight into the above.

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