# Si vs InterFast

The clearest difference is review sentiment: InterFast at 100% against Si's 0%. InterFast also leads on update cadence (every 2 weeks vs every 6 months). Si's advantage is iOS requirement (12.4 vs 15). On price, ads, in-app purchases and monetization model there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

Si ships an update every 6 months, InterFast every 2 weeks. Both last shipped on November 3, 2026.

## The numbers

| Metric | Si | InterFast |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[3.0 (1 ratings)](https://appshunter.io/ios/app/si-hvacr-measurement-mobileapp/id1475739979/reviews)** | — |
| Number of ratings | **1** | — |
| Positive reviews | 0.0% of reviews | **100.0% of reviews** |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 6 months | **Every 2 weeks** |
| Monetization | Free | Free |
| Size | 55 MB | 61 MB |
| Requires iOS | **12.4** | 15 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [SAUERMANN INDUSTRIE](https://appshunter.io/developer/1169513729) | [Interfast](https://appshunter.io/developer/1536410981) |

## What reviewers say

### Si

[App page](https://appshunter.io/ios/app/si-hvacr-measurement-mobileapp/id1475739979)

This application connects to specific Sauermann instruments to display real-time measurement data on your smartphone. It allows you to manage, save, and export measurement datasets in various formats, including PDF, CSV, and XML.

**Highlights:** Real-time measurement display, Data management, Report generation, Export to PDF, CSV, XML, Bluetooth connectivity, Measurement of temperature, humidity, pressure, air velocity

**In-app purchases:** none


### InterFast

[App page](https://appshunter.io/ios/app/interfast/id1536410979)

This all-in-one construction app simplifies business management with tools for quotes, invoices, and client portals. It offers features for project planning, site management, and financial tracking, including bank connections.

**Highlights:** Quotes, Invoices, Credit Notes, Price Library, Treasury & Bank Connection, Scheduling, Site & Intervention Management, Client Management & Portal

**Features:** Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Si free?

Si is free to download, with no in-app purchases.

### Is InterFast free?

InterFast is free to download, with no in-app purchases.

### Do Si or InterFast have ads?

Neither Si nor InterFast shows ads.

### Which is updated more often, Si or InterFast?

Si ships an update every 6 months, and InterFast every 2 weeks. Most recently, Si was updated on November 3, 2026 and InterFast on November 3, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*