Parity follows the principles behind IPMVP
Parity uses industry standard measurement and verification to calculate savings, following the International Performance Measurement and Verification Protocol (IPMVP).
IPMVP “Option B”
IPMVP “Option B” is used to measure electricity savings “This option is based on short-term, periodic, or continuous measurements of baseline and post-retrofit energy use (or proxies of energy use) taken at the component or system level. Savings are determined from analysis of baseline and reporting-period energy use or proxies of energy use”. The justification for this approach is that Parity only controls a portion of the building’s total use related to Heating, Ventilation and Air Conditioning (HVAC). This approach is more accurate with measurements taken at the individual equipment level, and any external noise is left out of the equation (lighting, plug loads, elevators, and any other process that Parity does not control). Weather normalization is applied where applicable (e.g.cooling tower)
IPMVP “Option C”
IPMVP “Option C” is used for measuring gas savings “This option is based on continuous measurement of energy use (such as utility billing data) at the whole facility or sub-facility level during the baseline and post-retrofit periods. Savings are determined from analysis of baseline and reporting-period energy data. Regression analysis is conducted to correlate energy use with independent variables such as weather and occupancy”. This is deemed as the most accurate approach since Parity controls both Domestic Hot Water and Heating in the building which covers the whole usage of gas in the building. This approach also takes weather impacts into account. Weather normalization is used to make an accurate comparison between the energy the building is currently consuming with Parity installed to what it would have consumed under the same weather conditions, without Parity.
Weather has a significant impact on the consumption behaviour of multi residential high rise buildings. A sizable portion of the total use is attributed to heating and cooling the building (including the air). A like-for-like comparison must be done by either normalizing the data, or comparing months where the weather is almost identical. E.g. Compare a post retrofit month that has 240 Cooling Degree Days (CDD) with a pre retrofit (pre Parity) month that has the same number (or close enough) of CDDs.
Energy Price Changes
Parity uses a fixed energy cost from the time of the contract and reports on savings relative to this baseline, without relying on inflation to achieve the savings. If the building consumed less energy but energy costs increased, the savings may be partially masked. Just as with weather, energy costs must be normalized to the original baseline to compare.
Excluded Electrical Loads
Parity controls HVAC related equipment in the building, while the monthly bill includes the whole building’s use including lighting, garage fans, elevators, plug loads…etc. It may be difficult to reconcile consumption savings from the electrical bills if the occupancy of the building increased or if the lighting load changed.