Learn what NYC LL84 energy grades reflect, how ENERGY STAR scores translate into grades A through F, and how to improve your score.
BY NYC Energy Code Team
ON
24 September 2026
How Weather Normalization Affects Your LL84 Benchmarking Score
A building can use more energy this year than last year and still have better weather-adjusted performance.
That sounds counterintuitive, but it is one of the most important concepts to understand when reviewing NYC Local Law 84 (LL84) benchmarking data.
Weather normalization helps separate changes caused by the weather from changes caused by the building itself. A particularly hot summer can increase cooling energy, while an unusually cold winter can increase heating consumption. Without adjusting for those conditions, comparing two years of energy data can give a misleading picture of whether the building actually became more or less efficient.
NYC requires covered buildings to submit annual energy and water consumption through the EPA's ENERGY STAR Portfolio Manager. Portfolio Manager uses weather and other operating characteristics when calculating the ENERGY STAR score for eligible property types.
What Is Weather Normalization?
Weather normalization is a statistical adjustment that estimates how much energy a building would have used under more typical weather conditions.
Portfolio Manager's current methodology uses the relationship between a property's energy consumption and outdoor temperature to estimate weather-adjusted energy use. The weather-normalized result represents the energy the property would have consumed under 15-year average weather conditions.
The important point is that your actual utility consumption does not disappear.
Suppose your building used:
1,000,000 kWh during an unusually hot year
Portfolio Manager may estimate that, under normal weather conditions, the building would have used:
930,000 kWh
The 1,000,000 kWh remains the building's actual consumption. The 930,000 kWh is a weather-normalized analytical value.
That distinction becomes important when evaluating trends.
Why Weather Can Distort Building Performance
Imagine two otherwise similar years.
In Year 1, the summer is relatively mild.
In Year 2, the summer is unusually hot.
The building's cooling system may operate much longer in Year 2. Electricity consumption therefore increases even though the HVAC system, controls, building envelope, and operating practices have not changed.
A simple year-to-year comparison could make the building appear less efficient.
Weather normalization asks a different question:
“How would the building have performed if both years had experienced comparable weather?”
That makes it easier to identify changes that are more likely related to the building itself rather than temperature differences.
Does Weather Normalization Change Your LL84 Filing?
No.
This is an important distinction.
Under LL84, the owner still needs to provide the building's actual energy and water consumption information for the applicable reporting period. NYC requires covered buildings to benchmark their energy and water consumption in Portfolio Manager and share the property with the City.
Weather normalization is part of how Portfolio Manager analyzes the data. It does not mean the owner should replace actual utility readings with weather-adjusted numbers when entering the property's meters.
Think of it as:
Utility bills → actual consumption → Portfolio Manager → weather/operating analysis → benchmarking metrics
Your source data should remain accurate even when the resulting analytical metrics are normalized.
How Weather Normalization Affects the ENERGY STAR Score
This is where the concept becomes particularly relevant to a building's benchmarking performance.
For property types eligible for an ENERGY STAR score, EPA compares the building's energy performance with similar buildings nationwide. The score accounts for weather variations and key property-use characteristics, and the comparison is based on source energy.
A score of 50 represents median performance within the applicable national reference population. Higher scores indicate better relative performance.
So your score is not simply:
“How many kWh did my building use?”
It is closer to:
“How does this building's energy performance compare with similar buildings after accounting for relevant differences such as weather and operating characteristics?”
That distinction is why a building with a high raw energy consumption may still receive a better score than another building with lower raw consumption if the two properties have substantially different characteristics.
Weather-Normalized EUI vs. ENERGY STAR Score
These terms are often mixed together, but they are not identical.
1
Weather-Normalized EUI
Weather-normalized EUI shows energy use intensity after adjusting for weather.
Weather-normalized source EUI = weather-adjusted source energy ÷ building area
Portfolio Manager provides weather-normalized site and source energy metrics.
2
ENERGY STAR Score
The ENERGY STAR score is a 1–100 comparative performance score for eligible property types.
It uses statistical modeling to compare the property's energy performance with similar buildings while accounting for weather and relevant operating characteristics.
So:
- Weather-normalized EUI = performance metric
- ENERGY STAR score = comparative ranking
Both can be useful, but they answer different questions.
A Simple Example
Imagine an office building has the following results:
| Metric | Year 1 | Year 2 |
|---|---|---|
| Actual electricity use | 900,000 kWh | 1,020,000 kWh |
| Weather-normalized energy | 930,000 kWh | 950,000 kWh |
| ENERGY STAR Score | 72 | 75 |
At first glance, Year 2 looks worse because actual electricity consumption increased by 120,000 kWh.
But Year 2 may have experienced substantially hotter weather.
After weather adjustment, the estimated energy difference is much smaller. The ENERGY STAR score also increased.
That does not automatically prove that the building became more efficient. Other changes in operating characteristics, data inputs, or the building's performance relative to the national reference population can affect the score.
But it illustrates why raw consumption alone is not enough to evaluate benchmarking performance.
Heating and Cooling Are Particularly Sensitive
Weather normalization matters most when outdoor temperature has a strong relationship with building energy consumption.
For many commercial properties, that means heating and cooling.
A winter with unusually low temperatures can increase:
Boiler/furnace operation → heating energy → total energy consumption
A summer with unusually high temperatures can increase:
Cooling load → chiller/AC operation → electricity consumption
A weather-normalized metric attempts to account for those temperature-driven effects so that changes in underlying performance can be evaluated more fairly.
Why This Matters for NYC Building Owners
NYC's benchmarking program is designed to make building energy performance measurable and comparable. The City uses ENERGY STAR Portfolio Manager as the required benchmarking platform for LL84.
That means owners reviewing their annual results should not simply ask:
“Did our energy use go up or down?”
They should also ask:
- “Did the weather change?”
- “Did occupancy or operating hours change?”
- “Did the property-use information change?”
- “What happened to our weather-normalized metrics?”
- “What happened to the ENERGY STAR score?”
That combination provides a much more useful performance picture.
Weather Normalization Is Not the Same as an Energy Audit
Weather normalization can tell you that performance changed after accounting for weather.
It generally cannot tell you why.
Suppose a building's weather-normalized energy use is rising.
That could be associated with:
- Poor HVAC controls
- Longer operating schedules
- Equipment deterioration
- Increased occupancy
- Changes in tenant operations
- Building-envelope problems
The benchmark identifies a signal. An energy audit, retro-commissioning investigation, or detailed engineering analysis can help identify the underlying causes.
This is why benchmarking is often most useful as the starting point for investigation, rather than the final diagnosis.
Why Accurate Building Information Still Matters
Weather is only one factor in the ENERGY STAR score methodology.
EPA states that the score also accounts for changes in key property-use details and other characteristics that influence energy consumption.
That means incorrect information about the property can affect the analysis.
For example, owners should pay attention to:
Gross floor area + property type + operating characteristics + occupancy/use data + complete energy records
NYC's current LL84 guidance specifically tells owners to check energy data for completeness and verify building characteristics and property-use information in Portfolio Manager.
Can a Hot Year Actually Improve Your Score?
It is possible for actual energy use to increase during a hot year without the building necessarily becoming less efficient relative to its peers.
That is precisely why weather adjustment exists.
However, it would be incorrect to assume:
“Weather was bad, so the ENERGY STAR score doesn't matter.”
The score still incorporates the building's energy performance after statistical adjustments. A significantly higher or lower score can reflect more than weather alone.
The right interpretation is therefore:
- Actual use tells you what happened.
- Weather-normalized metrics help explain the weather effect.
- The ENERGY STAR score shows relative performance after the methodology's adjustments.
What About Buildings Without an ENERGY STAR Score?
Not every property type in Portfolio Manager is eligible for a 1–100 ENERGY STAR score. EPA identifies specific property types for which the scoring methodology is available.
For properties without a score, weather-normalized EUI and other Portfolio Manager metrics can still be valuable for tracking performance over time.
This is particularly important because owners should not confuse benchmarking data with energy grading. A building can submit LL84 benchmarking data even when its property type does not receive an ENERGY STAR score.
NYC's energy-grading framework uses ENERGY STAR scores for applicable scored properties.
How to Read Your Benchmarking Results More Intelligently
Instead of looking at one number, review the relationship between several metrics.
A useful sequence is:
Actual Energy Use → Weather-Normalized Energy → Weather-Normalized EUI → ENERGY STAR Score, where applicable → Building systems and operating conditions
This approach helps distinguish weather effects from potential building-performance problems.
Common Mistakes
1
Comparing Raw Energy Use Between Years
A hotter or colder year can make raw consumption comparisons misleading.
2
Assuming Weather Normalization Guarantees a Better Score
Weather normalization is one part of the ENERGY STAR methodology. The score also considers relevant operating characteristics and compares performance with a national reference population.
3
Entering Weather-Adjusted Numbers Instead of Utility Data
Benchmarking should be based on the property's actual energy consumption data. Portfolio Manager performs the relevant analytical adjustments.
4
Treating the ENERGY STAR Score as an Engineering Diagnosis
The score can reveal relative performance but cannot identify a failing pump, poorly calibrated sensor, leaky envelope, or other specific problem.
A Better LL84 Benchmarking Review
After completing the annual LL84 submission, compare the current year with previous years.
Look at:
Actual consumption → weather-normalized consumption → EUI → ENERGY STAR score → operational changes
Then ask what changed in the building.
A sudden shift may be associated with a new tenant, different operating hours, an HVAC change, unusual weather, missing utility data, or an actual efficiency problem.
This type of review turns LL84 benchmarking from a filing obligation into a building-performance management tool.
Conclusion
Weather normalization helps put your LL84 benchmarking data into context.
A hot summer or unusually cold winter can change a building's actual energy consumption even when the building's underlying efficiency has not changed. Portfolio Manager addresses this by producing weather-normalized metrics and incorporating weather into the ENERGY STAR score methodology for eligible property types.
For NYC building owners, the most useful approach is to look at more than the raw utility numbers. Compare actual energy use, weather-normalized EUI, and the ENERGY STAR score, while also checking whether occupancy, operating hours, property information, or major building systems changed.
And remember the key distinction: LL84 requires accurate actual energy data to be benchmarked; weather normalization is an analytical adjustment performed within Portfolio Manager.
Used correctly, weather normalization makes year-to-year benchmarking more meaningful and gives owners a better starting point for identifying genuine energy-performance opportunities.
Frequently Asked Questions
No. Owners should submit accurate energy consumption data for the applicable reporting period. Portfolio Manager uses that data to calculate weather-normalized metrics and the ENERGY STAR score where applicable.
It is an estimate of the energy a property would have used under average weather conditions rather than the exact weather experienced during the reporting period. Portfolio Manager currently bases this metric on 15-year average weather conditions.
Yes. EPA states that the ENERGY STAR score methodology accounts for weather variations as well as relevant property-use characteristics.
A building's raw energy use can increase because of weather or other operating conditions. The ENERGY STAR score compares performance after accounting for relevant factors in its methodology, so a higher raw consumption does not automatically mean a lower score.
No. Weather-normalized EUI is an energy-intensity metric, while the ENERGY STAR score is a 1–100 comparative performance measure for eligible property types.
No. It helps account for weather when evaluating performance, but it does not diagnose specific equipment or operational problems. A detailed energy audit or engineering investigation may be needed to determine the cause.
No. ENERGY STAR scores are available only for eligible property types under EPA's scoring methodology. Other properties can still have benchmarking and weather-normalized energy metrics in Portfolio Manager.