  Upgraded electronics, improved water system dynamics, better calibration and
analysis techniques allowed Super-Kamiokande-IV to clearly observe very
low-energy 8B solar neutrino interactions, with recoil electron kinetic
energies as low as 3.49 MeV. Super-Kamiokande-IV data-taking began in September
of 2008; this paper includes data until February 2014, a total livetime of 1664
days. The measured solar neutrino flux is (2.308+-0.020(stat.) +
0.039-0.040(syst.)) x 106/(cm2sec) assuming no oscillations. The observed
recoil electron energy spectrum is consistent with no distortions due to
neutrino oscillations. An extended maximum likelihood fit to the amplitude of
the expected solar zenith angle variation of the neutrino-electron elastic
scattering rate in SK-IV results in a day/night asymmetry of
(-3.6+-1.6(stat.)+-0.6(syst.))%. The SK-IV solar neutrino data determine the
solar mixing angle as sin2 theta_12 = 0.327+0.026-0.031, all SK solar data
(SK-I, SK-II, SK III and SKIV) measures this angle to be sin2 theta_12 =
0.334+0.027-0.023, the determined mass-squared splitting is Delta m2_21 =
4.8+1.5-0.8 x10-5 eV2.
