Nothing in this part shall be construed to prohibit any public utility from profiting, to the extent permitted by the commission, from any economies, efficiencies, or improvements which it may make, and from distributing by way of dividends, or otherwise disposing of, such profits. The commission may make or permit such arrangement with any public utility as it deems wise for the purpose of encouraging economies, efficiencies, or improvements and securing the public utility making them such portion of the profits thereof as the commission determines.