The bus fare is free if you have a pre-booked ticket to Perlan. The bus has 19 seats.
You can buy an Observation Deck ticket on the bus for ISK 890. It includes:

→ Access to the 360° Observation Deck
→ A discount of ISK 890 on any exhibition ticket at Perlan
→ Bus fare on the day of your visit (both ways)

The shuttle bus departs from three locations:

Harpa                   Hótel Natura               Perlan
10:00 am               10:15 am              10:30 am > to Harpa
11:00 am                11:15 am               11:30 am
12:00 pm                     -                        12:45 pm
01:00 pm               01:15 pm               01:30 pm
02:00 pm               02:15 pm               02:30 pm
03:00 pm               03:15 pm               03:30 pm
04:00 pm               04:15 pm               04:30 pm
05:00 pm               05:15 pm                05:30 pm
06:00 pm > to Perlan, last stop