Generally speaking, A home inspection is a visual inspection of a home. An inspector is not able to look under or between floors or inside walls. While this is a standard limitation to an inspection, there are other sometimes other limitations that are imposed by circumstances. These circumstances might lead to a less than ideal situation. For example, it is not uncommon to find homes where the utilities are shutoff. This is frequently the situation at homes that are vacant. The seller might have had the home on the market for some time and decided to save money by disconnecting the utilities or, in cold weather, the decision could have been made to winterize the plumbing and have the main water turned off.
The likely scenario, and how it impacts the buyer, is that that person wants to buy the home and the inspection is scheduled to visit prior to the systems being turned back on. This is problematic and it is best if the realtors involved evaluate this situation and try to get utilities turned back on prior to the inspection. Needless to say if, when the inspector arrives, there is no electricity, no fuel (gas, propane, heating oil) and or no water, the inspection is very limited. Sometimes a few utilities are hooked up, but other key utilities are not. Whenever any combination of circumstances, such as described here, exist the inspection is very limited in scope.
When the water is off, an inspector cannot look for active leaks at sinks, tubs, toilets and other fixtures. Furthermore, the inspector cannot test the positioning of hot and cold water taps (hot water to the left), nor can the water pressure or the temperature of the hot water tank be evaluated. When electricity is off, outlets, lights and most things electrical (heaters, furnaces, electric water heaters, disposals, ranges, refrigerators) cannot be evaluated.
The inspector can look in the main electric panel, but that is about all. It is possible that the inspector might be able to determine if there are any GFCI outlets or see knob and tube or old two-prong systems. When gas is off furnaces, and often water heaters, go without being performance tested, other than a few visual checks. When these elements of the inspection are excluded, it decreases the quality of the inspection and the value to the client.
Home inspectors only operate normal controls, if you work in real estate, and do not know this. The inspector will not come in and start turning on the main water valve, the main breaker, the gas from the propane tank, etc. If these systems are inoperable when the inspector arrives, they will remain that way and not be evaluated. The reason: The inspector does not want to be responsible if turning on the main water leads to a ruptured pipe in the house, or if flipping the main breaker leads to a fire or electrical short. When main controls are turned off, it sometimes means there is a more serious problem in the home and an inspector cannot take the risk of finding out.