Performing M&V When You Have Solar

by ‐ Tags: alternative energy, tracking and benchmarking, green living

If you’ve installed solar panels as part of a building upgrade, congratulations!  But as you're patting yourself on the back, you may also be wondering "How do I show the savings from that retrofit?"  Without solar, it’s a pretty straightforward look at pre- and post-retrofit usage. But solar throws a wrench into that.  You likely now have a net meter and a utility bill with new line items that don’t make a lot of sense - kWh received, kWh delivered, net metering credit, etc. What's it all mean and can you gain any valuable insight from all these numbers?

Running Measurement and Verification When You Have Solar

When discussing measurement and verification (M&V) for solar, there is some good news. There are only two numbers you need to find to understand how much electricity is being used on-site and see how much that usage has decreased since improving your building.  

Those two numbers are net usage and corresponding solar production.  Once you have those numbers, you just add them together to calculate the amount of electricity used on-site.  After that you’re golden.  Just do your standard M&V using the amount of electricity used on-site and you’ll know how your retrofit is performing.  What’s that?  M&V isn't your cup of tea?  Don’t worry, we’ve got your back.

Even if you’re not running M&V, you’ll at least now have the numbers you need to see how the energy usage in your building has changed post-retrofit. Once you know how to arrive at the amount of electricity your building is using on-site, you’ll be able to make an accurate comparison between your usage post-upgrade and the usage before.   

The Nitty-Gritty of Net Usage and Solar Production

You may be thinking that I’ve glossed over some important details, such as where to find your net usage and solar production.  Production is usually the easier one.  Almost all solar companies provide access to an online solar dashboard that lets you see how many watts your PV produces each day. This daily granularity lets you determine exactly how much you produce during the billing period noted on your utility bill.  Worst case, there’s often a USB port on the inverter and you can manually download your production data.

Determining net usage is definitely trickier.  Some utilities do a great job clearly showing this in billing statements while others produce a rather useless mess still undecipherable even after you spend significant time with customer service reps to explain what each line means.  See below for some of the better utility bill examples.

Example 1

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To understand the current month’s net usage, ignore any carryovers from previous months.  This means that you can’t always go straight to the net kWh line and call it a day.  For this utility, we only want to look at the first two lines of information to find the net usage.

Example 2

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This utility bill is a little less clear than the first example.  Who exactly is the electricity being delivered to? And who is receiving it?  You? Or the utility company?  With a little investigating it becomes clear and it’s possible to determine the net usage.

Example 3

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The general format of this is similar to example 1, just with slightly different language.  Again, you want to ignore any carryover credits from previous months when calculating this month’s net usage.

Example 4

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This utility, despite having a rather information-dense bill to sort through, makes things simple and clearly shows your net usage.  

Each utility company has its own way of formatting bills for solar, but hopefully these examples point you in the right direction.  We understand that most people don’t want to get this involved with their utility bills since they can be so complicated.  If you have solar tracked in Wego, we’ll make sure to pull in the correct values from your utility bill as well as your production data so you can see the information that’s relevant to you without going cross-eyed looking at obscure line items on bills.   

 

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