What Is Hikari Denwa?
Hikari Denwa is a general term for IP phone services that use fiber optic lines. NTT East/West's "Hikari Denwa" is the most widely adopted, while KDDI's "au Hikari Phone Service" and SoftBank's "White Hikari Phone" offer similar services. Unlike traditional analog (copper) lines, Hikari Denwa digitizes voice data and transmits it over fiber optics, delivering higher call quality at a lower monthly cost. See also our VoIP basics guide.
In January 2024, NTT completed the migration of its analog fixed-line network (PSTN) to an IP-based network. While traditional analog lines now use IP technology behind the scenes, switching to Hikari Denwa lets you enjoy even greater cost savings. If you plan to continue using a landline, now is an excellent time to consider the switch.
Benefits of Hikari Denwa
Significant Monthly Cost Savings
The biggest advantage of Hikari Denwa is its low monthly fee. NTT's analog residential line costs 1,870 yen/month (tax included), while Hikari Denwa's basic plan is just 550 yen/month (tax included) - a saving of about 15,840 yen per year. However, Hikari Denwa requires a fiber optic internet subscription (e.g., Flets Hikari), so you need to compare total costs including internet fees.
- Basic fee - Analog 1,870 yen/month to Hikari Denwa 550 yen/month (saving 1,320 yen/month)
- Landline-to-landline calls - Analog varies by distance at 8.8-88 yen/3 min to Hikari Denwa flat rate of 8.8 yen/3 min nationwide
- Landline-to-mobile calls - Analog 17.6 yen/60 sec to Hikari Denwa 17.6 yen/60 sec (equivalent)
The flat nationwide rate is especially beneficial for long-distance callers. An analog call from Tokyo to Osaka costs 88 yen/3 min, but with Hikari Denwa it is just 8.8 yen/3 min - one-tenth the price.
Higher Call Quality
Hikari Denwa uses digital transmission, resulting in less noise and clearer audio compared to analog lines. Advances in VoIP technology have also greatly reduced the latency and packet loss issues that plagued earlier IP phones. However, call quality may degrade if your fiber bandwidth is congested or your router's performance is insufficient.
Rich Optional Services
Hikari Denwa offers options like Caller ID Display, Number Request, and Nuisance Call Rejection at lower prices than analog lines. The services covered in our landline nuisance call protection guide are available at reduced cost on Hikari Denwa.
Drawbacks and Considerations
Unusable During Power Outages
The biggest drawback of Hikari Denwa is that it does not work during power outages. Analog lines receive power from the telephone exchange and remain operational during blackouts, but Hikari Denwa requires your home router (ONU) to be powered. If you rely on your landline for emergencies, consider installing a UPS (uninterruptible power supply) or keeping a mobile phone as backup. A home UPS can keep your phone operational for a limited time during outages.
Fiber Optic Subscription Required
Hikari Denwa requires a fiber optic internet subscription such as Flets Hikari or a "Hikari Collaboration" service (Docomo Hikari, SoftBank Hikari, etc.). If you already have fiber for internet, the additional cost is minimal. If not, you will need to pay for line installation and a monthly internet fee. For phone-only use, SoftBank's "Ouchi no Denwa" (LTE-based, 1,078 yen/month) is also an option.
Some Numbers May Be Unreachable
Hikari Denwa may not be able to reach certain special numbers (some Navi Dial numbers, certain toll-free numbers). However, emergency numbers (110, 119) work without issue. See also the difference between toll-free and Navi Dial numbers.
Phone Number Portability
Portability Conditions
Whether you can keep your current phone number when migrating to Hikari Denwa depends on the type of number and the destination service. Understanding number portability will help you plan your migration.
- NTT subscriber numbers - Can be ported to NTT's Hikari Denwa within the same NTT exchange area
- Non-NTT numbers - Numbers obtained from KDDI or SoftBank may not be portable to NTT's Hikari Denwa
- When moving house - Portability may be possible within the same municipality, but numbers change when moving to an area with a different area code
Check portability in advance by calling NTT (116) or your carrier's customer support. If your number changes, you will need to notify contacts and update registrations with various services.
Suspending Your Number During Migration
You can also "suspend" your NTT subscriber number and migrate to Hikari Denwa. During suspension, no monthly fees are charged, and the number is retained for up to 10 years. If you might return to an analog line in the future, choose suspension over cancellation. Note that while using the same number on Hikari Denwa, the suspended number cannot be used separately.
Migration Steps
Steps for Migrating to NTT Hikari Denwa
The typical process for migrating from an analog line to NTT's Hikari Denwa is as follows:
- Step 1: Check your fiber connection - Confirm you have a Flets Hikari or Hikari Collaboration subscription. If not, start by applying for fiber
- Step 2: Apply for Hikari Denwa - Apply through NTT's website, by phone (0120-116-116), or at an NTT office
- Step 3: Confirm number portability - Check whether your current number can be ported. If not, a new number will be assigned
- Step 4: Schedule installation - NTT will contact you to arrange a date, typically 1-2 weeks out
- Step 5: Installation - On-site work (router setup and configuration) and exchange-side work are performed. On-site work takes about 1 hour
- Step 6: Connect your phone - Plug your phone into the router's (ONU) phone port. Your existing phone can be used as-is
- Step 7: Test - Make and receive test calls to confirm everything works
Installation fees range from 1,100 to 4,950 yen (tax included) for new setups. If you already have Flets Hikari, only exchange-side work is needed, keeping costs lower.
Pre-Migration Checklist
- Have you confirmed with NTT whether your current number can be ported?
- Have you checked your fiber optic subscription status?
- Do you have an alternative means of communication (mobile phone) for power outages?
- If you use a FAX, have you confirmed it will work with Hikari Denwa?
- Have you checked whether your security system or emergency alert device uses the phone line?
- Have you confirmed the migration procedure for optional services like Caller ID Display?
Pay special attention to home security systems and emergency alert devices. If these rely on an analog line, they may not function properly after migrating to Hikari Denwa. Check with your security provider in advance. A Hikari Denwa guidebook can help you understand the full picture before migrating.
Summary
Migrating to Hikari Denwa is a practical choice that delivers both lower monthly costs and better call quality. The benefits are especially significant for those who make frequent long-distance calls or already have a fiber optic connection. However, be aware of the power outage limitation and number portability conditions. Review the checklist above and contact NTT customer support with any questions before proceeding.