THE VALUE OF INTERVAL METER DATA
in solar PV project analysis
ETB Resource Guide
August 2015
Table of Contents
What is interval meter data
3
Who makes it available
5
Why is it better for analyzing solar PV projects
7
How to use and interpret raw data
9
About Energy Toolbase
11
Author:
Published:
Adam Gerza
August 4, 2015
THE VALUE OF INTERVAL DATA | SOLAR PV PROJECT ANALYSIS
3
What
is interval meter data?
“Interval data” or “meter data” is a series of measurements of energy consumption, taken at predefined intervals throughout the day. Typically interval meter data comes in increments of 60-minute,
30-minute or 15-minute granularity. The term “Interval data” is used interchangeably with “meter
data”, “raw data”, “demand interval data” and also “Green Button Data”. They basically all mean the
same thing, and are all captured by a digital or smart meter.
Units of measurement:
The main units of measurement of interval meter data are: kilowatt hours (kWh) or kilowatts (kW). kWh
measures energy or consumption over a period of time. kW measures power or the amount of energy
used at a given moment, which is commonly referred to as demand. You can derive one based on the
other using the formula:
energy (kWh) = power (kW) x time (hr)
Example: if the time interval is 15 minutes, the unit of measurement is kW, the value is 20, then:
kWh = 20 x 0.25
or
kWh = 5
Granularity of intervals:
Shorter intervals means more data points, and higher resolution data. Here’s the number of data points
captured over 1-year, depending on the interval.
interval period:
# of data points
1 day
1 month
1 year
60-min:
24
720
8,760
30-min:
48
1,440
17,520
15-min:
96
2,880
35,040
5-min:
288
8,640
105,120
THE VALUE OF INTERVAL DATA | SOLAR PV PROJECT ANALYSIS
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Green Button:
Green Button data (GBD) is basically interval meter data outputted into a standardized data format that
can be easily accessed via the click of a “green button”. The Green Button standard was created with
the support of the White House, the US Department of Energy
(DOE), and the National Institute of Standards & Technology
(NIST) to provide electricity customers with easy access to their
energy usage data in a consumer-friendly format. When
electric utilities use an interoperable data standard it
eliminates the need for software applications to support a
bunch of different data formats.
The two primary file types that Green Button data is downloaded into are: CSV (comma-separated
value) and XML (extensible markup language). CSV formatted data is generally read in Excel. XML is a
machine readable format, generally imported directly into a software application.
CSV format
XML format
THE VALUE OF INTERVAL DATA | SOLAR PV PROJECT ANALYSIS
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Who
makes interval data available?
With the rapid growth of: smart meters, advanced metering infrastructure (AMI) and real-time
communication networks, the number of electric utility customers who have access to interval meter
data has grown dramatically. According to the Green Button Data website “more than 60 million
households and businesses can use Green Button to access their energy usage data from their electric
utility.”
For many large C&I (commercial & industrial) customers, this data has been captured and logged for
decades. But now this data is becoming more accessible and ubiquitous, with the adoption of open data
standards like Green Button.
3 ways to get interval data from the utility:
1. Download via utility website
2. Get written authorization from customer, then request it from a utility service rep
3. Via a third party service like UtilityAPI
Download via utility website
Some utilities make raw interval data
available for download directly through
their customer web portal, which is
effectively the Green Button option.
For instance, in California all three investor owned utilities: Pacific Gas & Electric, Southern California
Edison and San Diego Gas & Electric – allow for direct download of Green Button data through their
websites. The logos below are URL hyperlinks to step-by-step instructions for downloading GBD data:
THE VALUE OF INTERVAL DATA | SOLAR PV PROJECT ANALYSIS
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Get authorization from customer
When the utility does not make GBD available for download via their website, it often times can be
retrieved from a utility representative. This route does require the host customers’ consent. A number
of utilities have template authorization forms to request billing and interval data file on behalf of a
customer. Here’s a URL hyperlink to a generic ‘Authorization to Receive Customer Information’ form.
Utilities have different internal systems in place for processing these requests. In some cases they have
the data AND make it available, in other cases they may have the data BUT choose not to make it
available, while some utilities may not have access to the raw data themselves. For utilities that do not
yet make Green Button data available for download via their website, it certainly can’t hurt trying this
route.
Via a third party service
Different types of third party services exist to access and retrieve interval data. They can be classified
into two general categories: services that get or fetch the data from the utility, or services that
independently meter and log the interval data, independent of the utility.
UtilityAPI is a popular software service that facilities
easy retrieval of interval data and utility billing data
from utility websites. Using the service, a solar
developer can send a link to the customer whose data
they want to access. The customer would securely
enter their utility login credentials and authorize that the data be sent directly to the requesting party.
This streamlines the data fetch and retrieval process for both parties.
There are an increasing number of products and service providers capable of capturing interval
consumption data, independent of the utility. While this route does require the installation of
hardware, like data loggers and communication gateways, it offers advantages over utility interval data
capture. One key advantage is the ability to capture the highest resolution data possible by determining
the interval period. For example, the eGauge Systems device allows for one second data capture, which
is 900 times higher resolution than 15-minute interval data. Another advantage is the ability to measure
circuit level loads, or the consumption from a specific appliance like an HVAC unit.
THE VALUE OF INTERVAL DATA | SOLAR PV PROJECT ANALYSIS
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Why
is interval data better for analyzing solar projects?
Interval meter data is better because it’s higher resolution. It contains significantly more data points
than the alternative, which is monthly summary data taken from utility bills. Having higher data fidelity
allows for a more detailed level of analysis.
# of data points in 1 month:
1
744
2,976
monthly utility bills
60-min interval data
15-min interval data
Advantages of working with interval data vs. monthly summary data when
analyzing and proposing solar PV projects:
Find the best utility rate option: utilities are increasingly offering multiple rate schedule options to
customers, many of which are time-of-use (TOU) based. Interval data makes it possible to precisely
quantify the dollar savings of the proposed project on each available option.
Practical use case: we pulled interval data on a random sample of 30 existing residential solar
system owners in California. We analyzed if these homeowners would save more money
staying on the (default) tiered rate, or opting onto the (voluntary) time-of-use based rate.
•
•
•
•
70% were better off on the TOU rate schedule
5% were better off on the tiered/block rate schedule
25% no net dollar difference, because the homeowner had a ‘full-offset’ system
on average, the TOU rate saved the customer an additional 36% annually
Simulate kW demand reductions from PV: interval data depicts the load profile of a customer, which
illustrates when demand charges occur. Having the raw data file allows a developer to ethically
estimate the reduction of demand charges in both kilowatts and dollars.
THE VALUE OF INTERVAL DATA | SOLAR PV PROJECT ANALYSIS
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Practical use case: demand charges make up 45% of the utility bill for a manufacturing facility.
The owner solicits two solar proposals. Using only monthly summary data, one proposal
makes arbitrary assumptions for the reduction of demand charges, which the customer feels is
naïve at best, and deceitful at worst. The winning developer requested the interval data file,
and simulated the reduction of demand charges in a transparent fashion.
System Optimization: on time-of-use based rate schedules, interval data is a prerequisite to determine
the optimal system size for dollar savings. The required inputs into the model are: interval meter data,
the solar system design specifications, and any utility rate switching options.
Practical use case: a sophisticated solar developer knows that time-of-use energy credits
cannot be carried forward at the end of a 12-month net metering cycle. Referencing their
customers’ interval data file, the developer uses software to simulate different system sizes,
ensuring they don’t leave money on the table by sizing a system that’s too big.
Future net metering frameworks: in a traditional net metering framework where kWh exports to the
grid are compensated at the full retail rate, calculating the dollar savings of a solar project is easy. But in
any framework (i.e. value of solar tariff) where exports are compensated at a value less than the fullretail rate, interval data is required to precisely determine the dollar savings of the project.
Practical use case: a homeowner in Hawaii is considering going solar. The project developer
needs to design and optimize a solar system that minimizes exports to the grid, which are
compensated at a wholesale rate. Interval meter data is necessary to evaluate the dollar
savings and project economics.
Combining energy storage with solar PV: two of the most common value streams of customer-side-ofthe-meter energy storage projects are: peak demand shaving and time-of-use arbitrage. It’s impossible
to model either of these scenarios and determine to what extent energy storage makes sense for a
specific customer without raw meter data.
Practical use case: a commercial customer who already has solar wants to evaluate the
payback economics of adding an energy storage system, and eliminating the peak demand
charges that their solar system is not reducing.
Calculate realized dollar savings: to accurately quantify energy savings in dollars (i.e. the value of solar)
for an operational solar system, interval data is required in tandem with solar production data.
Practical use case: a commercial customer entered into a PPA agreement four years ago. The
customer definitively knows how much their system has been producing, and how much they
are paying their PPA provider. But they have no clear idea of their actual realized dollar
savings, because their rates have changed and their consumption patterns have changed.
THE VALUE OF INTERVAL DATA | SOLAR PV PROJECT ANALYSIS
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How
to use & interpret interval data?
The previous sections of this guide demonstrate that: (1) interval data is more ubiquitous and easy to
access than ever, and (2) having the data provides a number of valuable benefits. The question then
becomes,
Q: How do you use & interpret raw data to unlock the benefits?
A: (good) software
Whether it’s a homemade Excel spreadsheet or the most sophisticated software platform on the
market, here’s the basic set of functions the software must perform:
Import
Data
Utility rate
analysis
Model &
optimize
Output
proposal
Import:
The first step is importing the raw data into the software application and then normalizing that data into
a standard format. Interval data comes in different file types, like CSV, XML or PDF. Within each type
there are numerous ways the data can be structured. For example, in Excel the data could be arranged
in a single-column or multi-column format. The software tool must be able to import different file
types, and different file formats, as well as standardize different units of measurements and granularity
of intervals.
Utility rate analysis:
The next step is to translate the raw meter reads into dollar values. Interval data files do not contain
billing information and do not specify which utility rate schedule a particular meter is on. Therefore
once the data has been imported the user must define the utility rate schedule, in order for the
software to reconstruct the bill.
THE VALUE OF INTERVAL DATA | SOLAR PV PROJECT ANALYSIS
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For straightforward utility rate schedules like a “flat rate” recreating the utility bill is easy. For more
complicated schedules, like a “critical peak pricing rate, with time-of-use & demand charges” the bill
reconciliation process becomes considerably more complex. Adding to the complexity is the fact that
many rate schedules have sub-attributes, like the ‘baseline territory’ or ‘service voltage type’, which
determine how the bill is calculated. To properly account for all the various rate schedules and subattributes, the software application will likely reference a utility rates database.
Model & Optimize:
It’s best to think about this step in terms of the inputs (going in) and outputs (coming out) of the
software or model.
Inputs:
•
•
•
•
•
•
Interval meter data: granularity of intervals, units of measurement
General customer info: tax status, tax rates, utility escalation rate assumption, etc.
Utility rates: sub-attributes, rate tariff effective date, eligible rate switch options
Incentives: rebates, tax credits, depreciation, REC’s
Solar system specs: costing, equipment (panels/inverters/racking), design specs (tilt angle,
azimuth, shade), solar production calculator (PVsyst, PVSim, HelioScope, PV Watts, etc.)
Financing: transaction type (cash purchase, loan, lease, PPA, etc.), terms of the transaction
(interest rate, escalation rates, term, fees, etc.)
Outputs:
•
•
Avoided cost: dollar savings from solar on eligible utility rate options
Project economic metrics: pay-back period, return on investment (ROI), internal rate of
return (IRR), net present value (NPV), lifetime cost of energy (LCOE)
Given that all of the inputs and assumptions going into the model will dictate the outputs coming out,
it’s important for the software to be transparent. The less the software functions like a black box the
better. In terms of optimization, capable software should be able to optimize for any output, based on
the defined project inputs. For example, based on a customers’ unique usage profile, what solar system
size and design specifications will result in the optimal 20-year internal rate of return.
Proposal output:
To realize the full value of interval data, the analysis must be presented clearly to the customer. Fancy
modeling and optimization are only worthwhile if the results can be effectively communicated. Often
times the key takeaways that interval data illuminates will be abstract. For example, quantifying that it
makes sense for a customer to opt onto a voluntary TOU rate schedule, or determining the maximum
solar system size for a specific customer to ensure they don’t lose annual time-of-use energy credits.
Great proposals will communicate complex items like these clearly to the customer.
THE VALUE OF INTERVAL DATA | SOLAR PV PROJECT ANALYSIS
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About
Energy Toolbase
Energy Toolbase is an industry leading software platform for analyzing and proposing the economics of
solar and energy storage projects. Our SaaS product is used by hundreds of the leading developers
nationwide to accurately, objectively and transparently perform their utility rate analysis.
We think the future of solar project development will be all about interval data
and combined technology systems. We designed and built the Energy Toolbase
platform for that future, which in many ways is already here.
-- John Gurski, Founder & CEO
Product features: working with interval data
•
•
•
•
•
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Data import – best-in-class importation of interval data from any file format.
Utility rates engine – precise energy savings calculations in dollars. Our in-house utility rate
database spans over 30 states and 130 utility territories.
System optimization – determine the optimal sized system for dollar savings. Our simulation
engine references: interval data, solar design specs, and utility rate switch options.
Simulate demand reductions from PV – transparently quantify the reduction of demand
charges in kilowatts and dollars.
Energy Storage – objectively analyze the economics of energy storage projects with or without
PV.
Professional proposals – present analysis in a clear and logical fashion that speaks directly to
your customer. Customizable, interactive and visually stunning.
Sign-up for a free trial or demo at:
www.energytoolbase.com