Energy tracking is the most important thing

Energy Solutions Ltd

Tracking energy consumption is the most important analytic component of energy management.

The main reason for this is that often faults causing excess consumption happen quickly, and if the excess consumption can be discerned, then the problems can be identified and remedied to stop thee excess consumption.

All HVAC systems eventually have problems

Energy Solutions Ltd

The graph above shows the result of an air conditioning system trying to dehumidify unsuccessfully, and getting stuck in a “cooling runaway” 100% on, cooling but not dehumidifying. This took months to remedy, as it was a combination of a hardware fault and a software fault and difficult to trace. The problem cost an extra $150/day at its peak.

Similar control and operational problems that cost $100/day to $1,000/day regularly occur in large facilities. If these can be noticed and fixed in days, rather than months or years, the savings are clearly significant.

Problems of this magnitude are eventually visible even with simple tracking of energy costs, but this needs to be done regularly (generally at least monthly) to ensure that they are picked up.

For this simple tracking, just comparing the consumption/costs from the same month, previous year gives a reasonable value for comparison. Many companies will deliver this level of energy tracking.

Free downloadable reference documents are listed on the “Good Links” page.

Tracking temperature dependent baselines

Energy Solutions Ltd

In situations where the loads are weather dependent (heating and cooling), obviously the weather experienced during each billing period will have an impact. So, Energy Solutions uses a more sophisticated analysis with a temperature-dependent baseline to compare to, and eliminate this source of error.

The graph to the right shows the gas consumption of an indoor swimming pool complex with the baseline the light brown line and actual daily consumption the dark points. Both consumption and baseline vary a lot with temperature, but the actual was consistently lower than the baseline until the start of January 2017, when a control sensor fault caused the freeze protection to the solar heating to activate.

This caused daily gas consumption to more than double, costing an extra $200/day. Because the jump in gas consumption was noticed, it was fixed expediently.

This graph shows the successful implementation of a HVAC controls project, reducing whole-building electrical loads by over 10%.

Reporting energy cost reductions to stakeholders

Energy Solutions Ltd

In addition to the diagnosis of excess energy consumption, as described above, another main reason for energy tracking is for reporting to stakeholders, including management. With more emphasis on carbon emissions, many stakeholders want relevant information on consumption and emissions in an accessible format.

Management reporting like this is a separate process than the analytics, which are used to diagnose potential improvements.

Energy Solutions Ltd

Verification of energy savings

Finally, when energy-reduction projects are implemented, it is valuable to confirm that they have worked as intended, and that the energy consumption has actually improved as much as intended after the project was completed. (Again there is both a management reporting and a diagnostic/commissioning role for this process.)

This process is known as Verification (of energy savings), follows principles of statistical quality control, and is governed by a well-known international standard (the IPMVP, or International [energy] Performance Measurement and Verification Protocol).

Because of the necessity of doing this correctly (especially when payments are linked to energy savings, as in Performance Contracting), an international organisation has developed to support this, practitioners are certified by both local and international organisations (CEPNZ and AEE), and training courses and certification are regularly presented around the world.

In New Zealand, the certifying organisation is CEPNZ (Carbon and Energy Professionals New Zealand, The certification is linked to the international certification from the Association of Energy Engineers (AEE) and the standard is supported by the Efficiency Valuation Organisation

The process of verification consists of analysing distributions of energy consumption to determine a baseline (in our case, usually as a function of daily temperature), as an equation with a defined uncertainty within a given confidence level.

Robert Bishop has been accredited as a Certified Energy Measurement and Verification Professional (Level 2) by CEP and the (U.S.) Association of Energy Engineers.

Energy Solutions performs energy monitoring and Verification of energy performance for its own projects and also as an independent third-party assessments.

Attributable Carbon Emissions – are we doing it wrong?

Energy Solutions Ltd

The reduction in carbon (and other greenhouse gas) emissions resulting from energy efficiency projects is usually calculated by multiplying the reduction in energy consumption by an “emissions coefficient”, that represents the amount of CO2 equivalent released per unit of energy generated.

I believe that the “official” value used in New Zealand understates the carbon benefits from efficiency projects, and also understates the carbon costs from increasing electric demand.

The electricity emissions coefficient used in New Zealand varies year by year, and is regularly updated by the Ministry for the Environment. Typical emissions coefficients are about 0.19 kg CO2e per kWh of gas consumed (burned), and 0.12 kg CO2e per kWh of electricity generated.

These represent the average emissions for each source of energy. For electricity, this averages out the amount generated by hydro, wind and solar (with zero emissions) and other sources with higher emissions. The highest is coal, which emits about 0.60 kg CO2e per kWh generated.

Although the amount of CO2 emitted from burning gas (1) is relatively constant (the chemical composition of reticulated gas in New Zealand varies only slightly), the emissions attributable to electricity generation (2) are more complicated, and using the averaged coefficient published by MfE significantly undercounts the effect of energy efficiency improvements.

This is due to the nature of the New Zealand electricity generation system, whereby generation plant is dispatched based on a price bid by the owner of the generation plant. Usually hydro and wind, the zero-emission sources, are bid at the lowest price, so they are always dispatched, whereas fossil-fuel plant comes at the highest price.

The result is that all of the hydro and wind available are used. The variation in the amount of electricity generated is mostly in the amount of coal and gas burned to make up the difference between what the hydro can supply, and what the total demand is. Thus, by reducing the excess demand, electric energy efficiency almost always displaces electricity generated by burning fossil fuels, while having almost no effect on the amount of hydro and wind generation.

In 2006, the New Zealand electricity industry adopted an electric coefficient of 0.6, representing thermal plant usually running at the margin.


Using a higher emission coefficient, of 0.6 kg/kWh, better represents the value of energy saving projects and also the costs of increases in electricity demand.