An EnerGuide rating can improve substantially while the home’s modeled energy consumption barely changes. In one paired evaluation, the rating fell from 127 to 97 GJ/year. The follow-up record included an 8 kW solar PV system. Rated consumption went from 127 to 129 GJ/year.
The difference is in the renewable-energy contribution. It rose from zero to 32 GJ/year, more than offsetting the 2 GJ increase in modeled consumption. This case shows why the headline rating is only the start of the conversation.
The numbers behind the rating
| Reported quantity | Baseline | Follow-up | Change |
|---|---|---|---|
| Rated annual energy consumption | 127 GJ/year | 129 GJ/year | +2 GJ/year |
| Renewable-energy contribution | 0 GJ/year | 32 GJ/year | +32 GJ/year |
| Net EnerGuide rating | 127 GJ/year | 97 GJ/year | −30 GJ/year |
| PV capacity recorded in the model | 0 kW | 8 kW | +8 kW |
The arithmetic is straightforward: 127 − 0 = 127 at the baseline, and 129 − 32 = 97 at the follow-up. The net rating improved by 30 GJ/year, or about 24%, using the rounded report values.
That 24% is a change in the net modeled rating. It would be inaccurate to tell the homeowner that the house now needs 24% less energy to operate. In these records, consumption before the renewable contribution is slightly higher.
What changed in the house model
The two records describe the same dwelling. Heated floor area was unchanged, building volume was effectively unchanged, and the comparison found no differences in the wall, roof, window, door or floor construction inputs reviewed. Both files used HOT2000 version 11.13b43, the same EnerGuide ruleset and the same weather location.
The substantial new entry was solar PV: the follow-up house model recorded 8 kW of capacity. Its Homeowner Information Sheet credited 32 GJ/year of renewable energy. Those are entries in the evaluation records; installation and commissioning documents were not part of this review.
Why the airtightness result deserves a closer look
HOT2000 reports airtightness of 2.212 and 2.2881 air changes per hour at 50 pascals, with seven test points in each file. The equivalent leakage area at 10 Pa rose from 614.7 to 661.3 cm², an increase of about 7.6%. This expresses the test-derived leakage as an equivalent opening area; it does not locate a particular gap.
The model’s air-leakage and natural-ventilation heat-loss output rose from 22.9 to 25.0 GJ/year. Modeled space heating increased by about 1.6 GJ/year, accounting for most of the rounded 2 GJ increase in total consumption. The direction is consistent with a higher modeled infiltration load. Some cooling inputs also differ; a controlled re-run would be needed to separate the effects of individual input changes.
For an advisor, that is a reason to examine airtightness alongside the improved net rating. When work crosses or disturbs the air barrier, service penetrations and joints deserve attention so the barrier remains continuous. NRCan’s air-leakage guidance explains the importance of sealing those connections. The records alone do not identify a leak location or establish that the solar installation caused the change.
What this means for a homeowner
Read the rating alongside two questions: how much energy is the home modeled to consume, and how much renewable energy is credited against that consumption? Here, the second number explains the improvement. The distinction matters when comparing a solar proposal with insulation, air sealing or a heating-system change.
The results can inform that discussion without answering every question about the investment. Actual solar output needs production records. A bill comparison needs grid imports, exports, energy prices and charges over a defined period. Neither can be read directly from the 30 GJ rating change.
This follows how EnerGuide is intended to be used. Natural Resources Canada describes the rating as estimated net annual energy under standard operating conditions, and cautions that household utility use should not be expected to match it.
The useful result in this case: the net rating fell by 30 GJ/year while modeled consumption was almost unchanged. Reporting consumption and renewable contribution beside the rating makes that result clear.
About this comparison
This is a selected single-home example, based on two 2026 EnerGuide evaluation files and their corresponding Homeowner Information Sheets. The records were matched using dwelling information and the follow-up’s link to the prior evaluation. The evaluation dates were checked for chronological order.
The main energy values above are the rounded consumption, renewable contribution and net rating displayed on the homeowner sheets. The HOT2000 files were used to check the recorded PV capacity, software basis, building inputs and test data. Changes are calculated as follow-up minus baseline.
It is a comparison of recorded modeled performance, not a controlled solar-only experiment or a measured-savings study. It describes this pair of records, not the typical result for other homes. Property identifiers and the underlying private files are omitted.
