Other Factors to Consider

There are numerous variables that determine the viability of a solar energy project. Many of these variables were baked-into the year-one case studies1 presented on this website. Other factors involved—such as efficiency losses and system‑upkeep costs—act on a longer timescale and were left out of the analysis. It is important to keep in mind that the year-one case studies are not complete long-term feasibility studies. If you are using our case studies as a baseline to consider your own solar project, here are a few additional variables to keep in mind.

Household Energy Usage

HVAC2 is the primary driver of a household’s electricity consumption. Within our case studies, we utilized a model with an electric central heating system rather than a gas furnace. Your own location’s climate—and whether or not your house is heated with a gas furnace—will impact your energy consumption profile and your system requirements.

Energy consumption may vary due to items such as air conditioning units or windows becoming less energy efficient over time. When these items are replaced, they require less energy. This reduction in energy consumption effectively increases the offset of the solar array.

System Upkeep Costs and Efficiency Losses

Solar panels are often rated on their spec sheets to lose roughly 2.0% of their efficiency in their first year of operation, and roughly 0.5% each year after that. When a roof with solar panels is replaced, removing the solar panels only to reinstall them again can cost thousands. This impacts the internal rate of return (IRR) significantly and is the reason why the preferred option is to install solar panels on a new roof. Although it is not necessary to begin a solar project with a new metal roof, many consider this to be the ideal situation, since metal roofs often outlast the projected timeframe of solar projects by several years.

Roof Pitch

The amount of solar energy generated at a particular time and location can be calculated accurately with a formula, and one of the key variables in this formula is roof pitch. Fortunately, many people happen to have a roof that is well suited for solar energy production. (Our year-one case studies are based on a 6/12 roof pitch.) At more northern latitudes, south-facing roofs with steeper roof pitches maximize solar energy production, while closer to the equator, lower roof pitches perform better. If your roof orientation or pitch is unsuitable, a ground-mounted system might be a viable option. Installation costs for ground-mounted arrays are often comparable to—or slightly higher than—roof-mounted systems, depending on details such as permitting requirements and the distance from the array to your electricity panel.

Additional Notes on Case Studies, Weather Data, etc.

In the year-one case studies presented on our website (and YouTube channel), we used actual meteorological year (AMY) data from 2023 to produce the energy consumption and production profiles. This is consistent with the usage of historical wholesale energy prices for that same year for the real time energy pricing analysis. (Weather affects energy consumption. In turn, the aggregate of everyone’s energy consumption affects wholesale energy prices, which are also linked to numerous other factors.) Although the case studies exemplify important trends, the results of one year alone should not be used to extrapolate future data for an entire feasibility study.

ReOpt and PVWatts are fantastic resources to make your own estimations, especially if you have a completely unshaded roof. Neither of these resources requires you to provide your home address or receive a sales call. (Scenarian is not affiliated with ReOpt, PVWatts, or the U.S. Department of Energy.)

If your roof is partially shaded, a detailed shading study with a more advanced solar calculator might be useful. Click here to request a consultation with Scenarian. If you are interested in acting as the contractor for your own solar project, we can provide you with the technical documents often required for permitting.

  1. Net Metering, Real Time Array Optimization, Solar and Energy Storage with Real Time Energy Pricing, and Time of Use with Solar & Energy Storage ↩︎
  2. You may also have noticed that HVAC systems run intermittently, and the energy consumption profile used for our case studies appears to be fairly smooth; this is an artifact of the modeling software that was used to produce the dataset. One might wonder if this distorts the results of the analysis. However, breaking out the HVAC energy consumption and allocating it to more realistic time intervals has a minimal effect on the overall financial outcome. This is because the highs and lows average-out over time. Over the course of the entire year, the effect on the average energy bill amounts to less than one dollar. ↩︎