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Will Data Save Home Performance?

Posted by Charley Cormany, EFCA Executive Director

Having a good way to measure efficiency is valuable to the home performance industry for many reasons. Easy to obtain, low cost, accurate savings data can be used to better educate consumers, close sales and help crews use their time more effectively when installing upgrades. Accurate data enables rebate programs to maximize every dollar spent on incentives. Good data can help legislators understand the real value of energy efficiency in order to pass regulations to support it. As accountants have said for years, in order to manage something, you have to be able to measure it. Perhaps that’s where the phrase “watch your pennies and the dollars will take care of themselves” comes from.

Until recently though, measuring energy efficiency has been easier said than done. Fortunately, there are a number of new innovations in that are changing the efficiency measurement game, creating many new opportunities for the industry.


When it comes to measurement, the solar guys have it easy. Solar panels are connected to an inverter that changes the current from DC, created by the panels, to AC which is used in our homes. In most cases the inverter also has the ability to measure the output of the solar array. Therefore, it’s very easy to see how much you are saving with solar P.V. as you can track output and compare it to usage.

Measuring energy efficiency, however, is a different story. Unlike solar, energy efficiency (EE) upgrades typically involve installing several different measures that work in concert to provide savings. To physically measure the individual effects of your efforts, you would need to have a meter for every measure, and then somehow combine all of that information in order to provide a summary of your savings. As you might imagine, that is not really possible.


To get the most accurate information about EE savings you can use data loggers–essentially small measuring devices–to monitor a variety of parameters related to your project. Data loggers can measure a wide range of conditions in a home, such as air temperature, humidity, airflow, fan watt draw, etc. You can use this information to provide a comparison of the conditions before and after the retrofit. This is a very scientific and accurate way to quantify the effectiveness of home performance upgrades. It’s also time consuming and expensive. In most cases, this type of detailed analysis is only performed by folks with PhDs and research and development budgets.

However, little by little, this kind of accurate savings information is making its way into the home performance market. Today there are several “smart” thermostats that can accept inputs from a variety of sources such as data loggers, outdoor temperature sensors, and even weather information from the Internet. This second generation of smart thermostats can then adjust your heating and cooling system to maximize savings and comfort. Some manufacturers are including real time data monitoring and controls into their higher-end heating and cooling systems. These integrated systems can be very sophisticated and monitor things like A/C refrigerant charge and airflow on HVAC systems. Using information from built-in sensors, these integrated smart systems adjust airflow and heat output of the system to meet actual demands, which equates to higher comfort at a lower cost. The downside is that they are expensive and not readily available.


The other common way to measure savings is by analyzing utility bills. With a bit of training, an energy efficiency auditor can use utility bill data to identify usage patterns and opportunities. This works best if the auditor has at least one year’s worth of data.

The first step in this kind of analysis is to identify the lowest continuous energy use, known as base load. Once you have the base load information, you can compare it to daily usage and look for patterns, such as increases from air conditioning or lighting loads. Identifying peaks in energy use can help define reduction strategies specific to your home. For example, if your summer bills are high, a more efficient air conditioning system or a new pool pump might be a good solution for you.

Another benefit of utility bill data is the ability to check results after you have installed upgrades. If you have historical spending information, you can compare bills before and after the retrofit. This becomes the metric for how much you are saving. Utility bill information can be a powerful part of understanding a home’s overall energy use.

One of the challenges to this approach is that utility bill data isn’t always easy to come by. Utilities safeguard ratepayer information, as it can be very revealing. For example, after an energy audit I amazed a client by asking if the family had been on vacation during the month of September. Indeed they had been, but how did I know? No nighttime peak for lighting and very little usage all month–it’s not rocket science if you have access to energy bills. You can imagine how this information could be used against you if it fell into the wrong hands.


Advanced Metering Infrastructure (AMI) is an integration of smart devices and communication networks that allows for two-way communication between the utilities and the metered device.

The most basic application of this technology is remote meter reading, but AMI can also be put to much more sophisticated uses. For example, with customers’ permission, AMI can be used to remotely turn down air conditioners during periods of high demand, reducing the load on the grid. This type of program is known as demand response (DR). Participants receive a notification—typically through text or email–when a demand response event is taking place. The utility then controls the customer’s equipment to reduce its energy use. This allows the utility to reduce the load on the grid and avoid starting up dirty and expensive “peaker” power plants to meet spikes in demand.

There are other new applications of AMI data such as ZigBee-based energy monitors. ZigBee is a wireless communications protocol similar to WiFi. Software can use ZigBee signals to monitor electricity use in a building without needing a physical connection. Some ZigBee monitors can “profile” electrical devices and identify which one is operating at a specific moment in time.

This can be very useful when trying to track down problems in real time and identify large load concerns. Take, for example, the case of a well pump that gets stuck in the “on” position, increasing a customer’s electricity bill by hundreds of dollars a month. Until recently, the only way to identify a problem like that was to physically go to the location and identify the load, circuit by circuit (true story). With AMI data and ZigBee profiling, you could do a search for the load profile and identify the problem without setting foot on the premises.

AMI data and smart meters will finally allow the energy efficiency industry to actively and accurately measure energy savings and AMI is creating a path for third parties to have access to accurate, low-cost data. Think about the potential for a minute. What if a contractor could upgrade two similar houses and test which measures are most effective? Is R-38 in the attic good enough or is R-60 necessary? With AMI data, you could compare the results without data loggers or even visiting the home. The applications are only limited by your imagination (and some regulations).


By combining AMI data with new approaches to calculating efficiency, it’s now possible to move away from relying on energy models and to start basing policy on actual observed savings.

For example, PG&E has adopted an open source software platform known as the OpenEEmeter to calculate meter-based savings. This platform allows private companies, utilities, and regulators to calculate the energy savings from a large group of EE projects using a consistent set of methods. This allows them to use real data for comparisons instead of models.

Think about the potential when it comes to designing and implementing incentive programs. No more guessing or relying on complicated energy modeling software. You won’t have to wait until the program is over to get results, combing through months of data only to find out your savings were less than expected.

PG&E and other utilities are now using the ability to measure efficiency based on data, not predictions, to create incentive-based, pay-for-performance (P4P) markets. Tools like the OpenEEmeter and others will facilitate bringing aggregated energy savings to the procurement market.


If the industry as a whole can provide proof that the energy savings it has long claimed to provide are real, it will be a game changer. Private investors who have been interested in energy efficiency but hesitant to jump in without more tangible data will have the confidence to move forward. Rebate programs will be able to focus on things that have been shown to save energy instead of relying on modeling software predictions. Contractors will be able to analyze their projects and tailor their efforts towards the most effective measures.


Imagine for a moment you are a utility. State mandates require that you purchase a certain amount of energy from clean sources, giving solar and wind additional value.

For years, energy efficiency has been left out of this conversation, mostly due to the difficulty of predicting actual savings. But now that we can accurately quantify efficiency, it will be possible to bundle (aggregate) energy savings and sell them as portfolios on the open market, where they can be procured in the same way solar, wind, and other renewable sources are.


With these new tools, we are starting to be able to accurately calculate energy savings from retrofits and other energy-saving efforts. Finally, we will be able to quantify what many of us have known for years. Energy efficiency works, the savings are real, and using less energy is still the lowest cost option of any renewable energy strategy.

Charles Cormany
Executive Director
Efficiency First California

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