LSI Calculator vs Erebus Solar
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
LSI Calculator
This app provides tools and educational resources to help users manage water systems, focusing on eco-friendly treatments for pools and spas. It aims to make water maintenance accessible to everyone, regardless of their experience level.
- Water science education
- Pool and spa water management
- Eco-friendly treatment guidance
- NSF/ANSI Certified product information
- Tools for water system management
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Next Generation Water Science makes water (and the people who maintain it) look great. Next Generation Water Science makes eco-friendly water treatments for pools, spas, industrial and agricultural water systems. All products are NSF/ANSI Certified for purity and safety. Through education and helpful tools like this mobile app, Next Generation Water Science has helped people of all aptitudes manage water better.
Erebus Solar
This app helps solar professionals measure on-site shade using their phone's sensors. It generates horizon files compatible with leading PV design software, aiding in accurate solar production estimates.
- AR sun path visualization
- Automatic sky capture
- Sky Editor for obstruction tracing
- Annual solar access analysis
- PDF shade report export
- Horizon file generation for design tools
- Project organization by site
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Measure shade on site with the hardware already in your pocket. Erebus Solar was designed by an electrical engineer and an architect with years of experience designing solar systems around the world. We were fed up with the horizon-finding hardware the industry still relies on: dedicated devices that haven't been meaningfully updated in decades, are slow to use and slow to find a GPS fix, and analog tools that need paper, a pencil and a latitude template that may not exist for your site. Erebus Solar is our answer. Your iPhone already has the camera, compass and sensors the job needs. WHY HORIZON FILES MATTER Far-field shading from trees, terrain and neighbouring buildings is one of the largest sources of error in a PV production estimate. A measured horizon profile, captured on site, lets your design software model that shading instead of guessing. Erebus Solar produces horizon files that leading PV design tools such as HelioScope and PVsyst read directly, and PV*SOL accepts the same convention. CAPTURE • AR sun path: today's arc, the solstice and equinox arcs and the live sun drawn over the real sky • Tap the real sun to calibrate the compass to true north • Automatic sky capture: sweep the envelope band and frames capture themselves, no buttons • Sky Editor: review the stitched sky and trace obstructions by hand, so the report reflects what you saw ANALYSE • Annual solar access and TSRF for each array area • Month-by-month charts and the sun-path chart with your obstructions • Aerial view with each area's boundary and the solar envelope over satellite imagery EXPORT • PDF shade report with your company name and logo • Horizon files for HelioScope, PVsyst and PV*SOL, generated from the same capture • Share straight from the phone ORGANISE • One project per site, located by address or GPS, with status from Created to Completed • Areas for each roof face or ground section • Everything stored on your iPhone: no account, no upload Erebus Solar's outputs are a design aid for qualified professionals. Results depend on the phone's sensors, compass calibration and sky conditions; check them against your own observations and your design tool's simulation before relying on them. Privacy Policy: https://erebussolar.app/privacy Terms of Use: https://erebussolar.app/terms
Screenshots
Verdict
The clearest difference is review sentiment: LSI Calculator at 100% against Erebus Solar's 0%. LSI Calculator also leads on rating (4.4 vs 3.7) and device support (3 vs 1). Erebus Solar's advantage is update cadence (every 2 weeks vs every 2 months). On price, ratings volume, ads and in-app purchases there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
LSI Calculator holds the better App Store score, 4.4 against 3.7. Both are backed by a comparable volume of ratings — 5 and 3 respectively. Written reviews point the same way: 100% of LSI Calculator's written reviews are positive against 0% of Erebus Solar's.
LSI Calculator ships an update every 2 months, Erebus Solar every 2 weeks. The most recent releases landed on October 5, 2026 and October 14, 2026 respectively.
| Parameter | LSI Calculator | Erebus Solar |
|---|---|---|
| Price | Free | Free |
| Rating | 4.4 (5 ratings) — better | 3.7 (3 ratings) |
| Positive reviews | 100.0% of reviews — better | 0.0% of reviews |
| Number of ratings | 5 — better | 3 |
| Update frequency | Every 2 months | Every 2 weeks — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Free | Free |
| Devices | iPhone, iPad, iPod — better | iPhone |
| Requires iOS | 11.0 — better | 17.0 |
| Further details — not scored | ||
| Size | 52 MB | 19 MB |
| Age rating | 12+ | 4+ |
| Developer | Pure Planet Science & Technology, Inc. | Todd Evans |
Customer experience
LSI Calculator
Erebus Solar
In-app purchases
LSI Calculator
No in-app purchases
Erebus Solar
No in-app purchases









