Section 72. Notice and hearing; order fixing price of gas or electricity or requiring improvement

Before proceeding under a complaint presented as
  provided in section seventy-one, the commission shall  cause  notice  of
  such complaint, and the purpose thereof, to be served upon the person or
  corporation  affected  thereby. Such person or corporation shall have an
  opportunity to be heard in respect to the matters  complained  of  at  a
  time  and  place to be specified in such notice. An investigation may be
  instituted by the commission of its own motion as to any matter of which
  complaint may be made,  as  provided  in  section  seventy-one  of  this
  chapter,  or  to  enable  it  to  ascertain  the  facts requisite to the
  exercise of any power conferred upon it. After a hearing and after  such
  an  investigation  as  shall  have  been  made  by the commission or its
  officers, agents, examiners or inspectors, the commission may, by order,
  fix just and reasonable prices, rates and charges for gas or electricity
  to be charged by such corporation or  person,  for  the  service  to  be
  furnished  notwithstanding  that  a  higher  or  lower  price  has  been
  theretofore prescribed by general or special statute,  contract,  grant,
  franchise  condition,  consent  or  other  agreement, and may order such
  improvement in the manufacture, conveying, transportation,  distribution
  or  supply  of  gas,  in  the  manufacture,  transmission  or  supply of
  electricity, or in the methods employed by such person  or  corporation,
  as  will  in  its  judgment  be  adequate, just and reasonable. Any such
  change in price shall be upon such terms, conditions  or  safeguards  as
  the  commission  may  prescribe.  If  it  shall be made to appear to the
  satisfaction of the commission  that  the  public  interest  requires  a
  change  in the price of gas or electricity charged by any such person or
  corporation, or that  such  change  is  necessary  for  the  purpose  of
  providing adequate and efficient service, or for the preservation of the
  property,  the  commission, upon such terms, conditions or safeguards as
  it deems proper,  may  authorize  an  immediate,  reasonable,  temporary
  increase  or decrease in such price pending a final determination of the
  price to be thereafter charged by such person or corporation. The terms,
  conditions or safeguards  prescribed  may  include  provisions  for  the
  purposes  for  which  the  additional  revenue  derived  from  any  such
  temporary increase may be expended and for the impounding thereof  until
  the  same shall be applied to the purposes so specified. The price fixed
  by the commission under  this  section  or  under  subdivision  five  of
  section  sixty-six  shall  be  the  maximum  price to be charged by such
  person, corporation or municipality  for  gas  or  electricity  for  the
  service  to  be  furnished  within  the territory and for a period to be
  fixed by the commission in the order, not exceeding three  years  except
  in  the  case  of  a  sliding scale, and thereafter until the commission
  shall, upon its own motion or upon the  complaint  of  any  corporation,
  person  or  municipality interested, fix a higher or lower maximum price
  of gas or electricity to be thereafter charged. In determining the price
  to be charged for gas or electricity the  commission  may  consider  all
  facts which in its judgment have any bearing upon a proper determination
  of  the  question although not set forth in the complaint and not within
  the allegations contained therein, with due regard among other things to
  a reasonable average return upon capital actually expended  and  to  the
  necessity   of  making  reservations  out  of  income  for  surplus  and
  contingencies. At any hearing involving a rate, the burden of  proof  to
  show  that  the  change  in  rate  or  price  if proposed by the person,
  corporation or municipality operating such utility, or that the existing
  rate or price, if on motion of the commission or in  a  complaint  filed
  with  the commission it is proposed to reduce the rate or price, is just
  and reasonable shall be upon the  person,  corporation  or  municipality
  operating  such  utility; and the commission may give to the hearing and

  decision of such questions preference over all other  questions  pending
  before  it  and decide the same as speedily as possible. Nothing in this
  chapter contained shall be deemed to prohibit the commission from fixing
  a  sliding scale upward rate for natural gas, beginning at a fixed price
  per unit for a small consumption and then increasing the price per  unit
  as the consumption is increased.