(1) Unless and until the commission shall have certified that the same is required by public convenience and necessity, no public heating utility shall acquire, construct (or materially change through reconstruction), install, or place in utility operation:

1. (a) Any facilities for providing service in a municipality in which the utility has not heretofore rendered service.
2. (b) Any facilities for providing service outside the area or areas submitted in response to s. PSC 140.015.
3. (c) Any heating plant or principal heat-absorbing, fuel-burning, or pumping unit.
4. (d) Any change in the method of transmitting heat to the customers, such as change from hot water to steam.
5. (e) Any building or addition to an existing building the cost of which exceeds $5,000 or 3% of the system’s gross heating operating revenue for the previous calendar year, whichever is the greater.
6. (f) Any mains or distribution or transmission facilities in the area where the utility has theretofore been operating which is estimated to involve a gross capital expenditure in excess of $500 or 3% of the system’s gross heating operating revenue for the previous calendar year, whichever is the greater.

(2) Unless and until the commission shall have certified that the same is required by public convenience and necessity, no utility other than a heating utility shall construct (or materially change through reconstruction), install, or place in operation:

1. (a) Any facilities to provide heat to new customers or facilities the end or by-product of which are to be used temporarily or permanently to provide heat to new or existing customers.
2. (b) Any added facilities or building estimated to cost more than $500 necessary to serve heat to existing customers.
3. (c) Any change in method of supplying such services.