How we make this list: we compare pricing pages, product documentation and public user reviews. Rankite is independent; if a vendor ever pays for a featured spot, that listing is clearly labeled Partner.
Key takeaways
- ENERGY STAR Portfolio Manager is the free starting point for benchmarking any commercial building, and many regulations require it.
- RETScreen Expert is the best free option for detailed project analysis, with strong financial modeling built in.
- Ekotrope dominates the HERS rating market for new homes, with 1 in 4 new US homes modeled in it.
- Snugg Pro is the only DOE-approved platform for IRA home efficiency rebate audits, which matters if you work with those programs.
Quick comparison
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The contenders in detail
Starting priceFree
Free planYes
Portfolio Manager is the EPA's free online tool for tracking energy and water use across buildings. You enter utility data and building characteristics, and it calculates an ENERGY STAR score from 1 to 100. Many cities now require benchmarking through this exact platform, which makes it mandatory rather than optional for covered buildings.
The strength is standardization. Everyone uses the same metrics, so scores are comparable. The weakness is effort. Manual data entry for a large portfolio takes real time, and the tool benchmarks rather than models, so it will not tell you which retrofit to do first.
What we like- Completely free
- Required by many benchmarking ordinances
- Large peer comparison database
Watch out for- Data entry is manual and tedious
- Limited modeling depth
Starting priceFree
Free planYes
RETScreen Expert comes from Natural Resources Canada and covers energy efficiency, renewable energy, and cogeneration project analysis. It includes financial modeling with payback, NPV, and emissions calculations. For a free tool, the depth is remarkable.
The catch is the platform. It runs on Windows and the interface shows its age. But if you need to evaluate whether a solar array or boiler upgrade pencils out, and you have no budget for software, this is where you start.
What we like- Full feasibility and financial analysis free
- 36 languages
- Strong clean energy models
Watch out for- Windows only
- Interface feels dated
Starting priceSee website
Free planFree trial (14 days)
Snugg Pro is built for home performance contractors who need to turn audits into sold upgrades. It generates professional homeowner reports with savings estimates, costs, and rebate information. It is the first platform approved by the US DOE for IRA Home Efficiency Rebate program audits, which is a decisive advantage if you work in that space.
The limitation is scope. This is a residential tool, period. Commercial auditors should look elsewhere. Pricing is quote-based, so you will need to talk to sales, though a 14-day trial lets you evaluate it first.
What we like- DOE-approved for IRA rebate audits
- Fast homeowner reports
- BPI-2400 compliant
Watch out for- Residential only
- Pricing is not public
Starting priceSee website
Free planNo
REM/Rate has been rating homes for decades and remains a workhorse for HERS providers. It calculates heating, cooling, hot water, lighting, and appliance loads, and handles ENERGY STAR, DOE Zero Energy Ready, and code compliance analysis. The component libraries are extensive.
The honest weakness is the user experience. Compared to cloud-based competitors like Ekotrope, REM/Rate feels like desktop software from another era, because it is. It is Windows only. Raters who value familiarity over modern workflow still choose it, but new raters increasingly go elsewhere.
What we like- Long-established HERS rating tool
- Detailed component libraries
- Code compliance built in
Watch out for- Windows only
- Interface lags modern competitors
Starting priceSee website
Free planNo
Ekotrope RATER is the market leader in HERS rating software, used for nearly 80 percent of all HERS ratings according to the company. It is cloud-based, so teams collaborate in real time without passing files around. Calculations that take a minute in other tools complete in about a second here.
The tradeoff is that this is professional software with professional pricing. There is no public price list, and the feature set assumes you rate homes regularly. If you do a handful of ratings a year, the cost and complexity may not justify the switch from a simpler tool.
What we like- Used for 1 in 4 new US homes
- Cloud-based with real-time collaboration
- Very fast calculations
Watch out for- Pricing is quote-based
- Overkill for occasional raters
Starting priceSee website
Free planFree trial (30 days)
EnergyCAP centralizes utility bills, meter data, and emissions into one platform. It audits bills for errors, benchmarks buildings, and tracks cost avoidance from efficiency projects. Organizations managing dozens or hundreds of buildings use it as their system of record for energy data.
This is not a tool you set up in an afternoon. Implementation involves data imports, rate structures, and workflow configuration. Pricing is not published, which tells you it is aimed at mid-size and large organizations. A 30-day trial of the Express version gives smaller teams a way to evaluate it.
What we like- 40+ years in energy management
- Strong bill auditing
- Carbon tracking included
Watch out for- Enterprise pricing not public
- Implementation takes time
Starting priceFree
Free planYes
eQUEST is a free building energy simulation tool based on the DOE-2 engine. It performs detailed hourly simulations of building energy use, which is the level of rigor needed for serious retrofit analysis or new construction modeling. Universities teach it, and many engineers learned simulation on it.
The learning curve is the barrier. This is not a guided audit wizard; it is a simulation engine that expects you to understand building physics. The interface is dated. But for free, there is nothing else that does hourly whole-building simulation at this depth.
What we like- Free DOE-backed simulation
- Detailed hourly analysis
- Widely taught in universities
Watch out for- Steep learning curve
- Dated interface
Starting priceFree
Free planYes
OpenStudio is the open-source platform for building energy modeling, developed with the National Renewable Energy Laboratory. It provides a graphical interface and software development kit on top of the EnergyPlus simulation engine. Researchers and advanced practitioners use it for custom analysis that commercial tools cannot do.
This is a tool for people who are comfortable with technical software. There is no sales team, no onboarding call, and the documentation assumes knowledge. But if you want a free, transparent, extensible modeling platform, OpenStudio is the answer.
What we like- Free and open source
- Backed by NREL
- Strong scripting and API
Watch out for- Requires technical skill
- Less hand-holding than commercial tools
What to look for in audit software
Start by defining what kind of audit you perform. Residential raters need HERS compliance and homeowner-friendly reports, which points to Ekotrope, REM/Rate, or Snugg Pro. Commercial auditors need benchmarking and bill analysis, which points to Portfolio Manager and EnergyCAP. Engineers doing detailed simulation need eQUEST or OpenStudio.
Check compliance requirements before anything else. If you rate homes for ENERGY STAR certification or HERS, your software must be RESNET accredited. If you work with IRA rebate programs, Snugg Pro's DOE approval matters. If your city mandates benchmarking, you will use Portfolio Manager regardless of what else you buy.
Evaluate the data workflow honestly. The best modeling engine in the world is useless if getting data into it takes longer than the analysis. Cloud-based tools with mobile data collection save hours on every audit. Desktop tools with manual entry cost you that time back.
Consider who else touches the output. If homeowners need to understand the report, prioritize clear visuals and plain language. If engineers or program administrators are the audience, prioritize data depth and export options. The right tool matches the reader, not just the analyst.
Finally, test the free options first. Portfolio Manager, RETScreen, eQUEST, and OpenStudio cost nothing. Many auditors find that a combination of free tools covers their needs, and you should only pay when you have identified a specific gap that free software cannot fill.
Do not overlook training and support when you compare. A tool with excellent documentation, active user forums, and responsive support will save you more time than a slightly better modeling engine with no help available. Check whether the vendor offers onboarding, and ask other auditors in your network what the support experience is actually like before you sign a contract.
How we chose
We evaluated eight energy audit tools using official product pages, documentation, and DOE and EPA resources. We prioritized tools that are actively maintained and relevant in 2026, covering residential rating, commercial benchmarking, utility management, and building simulation. We drew on public reviews from G2, Capterra, and industry forums to check real-world usability, and we verified compliance claims against RESNET and DOE published lists. No hands-on testing was performed.
Single-family homes and the HERS ecosystem revolve around Ekotrope, REM/Rate, and Snugg Pro. Choose based on volume and workflow preference. High-volume raters benefit most from Ekotrope's speed and collaboration. Contractors selling upgrades benefit most from Snugg Pro's reports. Traditionalists stick with REM/Rate.
Commercial buildings start with Portfolio Manager for benchmarking, then add depth as needed. EnergyCAP suits organizations managing many buildings and utility accounts. RETScreen suits project-level feasibility analysis for retrofits or renewables.
New construction and deep retrofits need simulation. eQUEST and OpenStudio provide the hourly modeling that simpler tools cannot. These require the most skill but deliver the most insight. Many firms pair a simulation tool with a simpler audit platform, using each where it fits best.
Frequently asked questions
What is the best free energy audit software?
ENERGY STAR Portfolio Manager is the best free option for commercial benchmarking, and RETScreen Expert is the best free option for detailed project analysis. eQUEST and OpenStudio provide free building simulation. The right free tool depends on whether you audit homes or commercial buildings.
Do I need certified software for a HERS rating?
Yes. HERS ratings must be performed with RESNET-accredited software. Ekotrope RATER and REM/Rate are both accredited options. Using non-accredited software means the rating will not be recognized, so verify accreditation before you commit to a platform.
What software do I need for IRA rebate audits?
Snugg Pro is the first platform approved by the US DOE for IRA Home Efficiency Rebate program audits. Requirements vary by state program, so check with your state energy office, but Snugg Pro's approval makes it the safest choice for this work.
Can I do an energy audit with just a spreadsheet?
You can track utility data in a spreadsheet, and many auditors start there. But dedicated software adds weather normalization, peer benchmarking, and standardized calculations that spreadsheets cannot easily replicate. For professional work, especially where certification or rebates are involved, proper software is expected.
How much does energy audit software cost?
Free tools cover benchmarking and basic analysis. Professional HERS rating software and enterprise platforms use quote-based pricing that varies by volume and features. Expect to contact sales for exact numbers on commercial tools, and budget for training alongside the license.
Sources we checked (8)
- https://www.energystar.gov
- https://www.retscreen.net
- https://snuggpro.com
- https://www.remrate.com
- https://www.ekotrope.com
- https://www.energycap.com
- https://www.doe2.com
- https://www.openstudio.net
Is your product missing or out of date?
We review this list regularly. Vendors can request a listing, send updated pricing or ask about featured placement.
Shihab Mia · Founder, Rankite
Shihab has spent more than a decade helping SaaS and e-commerce brands grow through search. He writes Rankite's software buying guides from pricing pages, documentation and public user reviews. More about Shihab.
ENERGY STAR Portfolio Manager
RETScreen Expert
Snugg Pro
REM/Rate
Ekotrope
EnergyCAP
eQUEST
OpenStudio