Low voltage can also happen if you live in a rural area and demand has increased without scrutiny from the utility. In my case the first winter I was here I had voltage at the meter from 97-104 volts. This will cause a lot of things to not work quite right, but you'd be surprised how many household appliances still pretty much work.

The utility acted quickly in my case when they were notified. An easy way to check is to have an electrician measure the voltage on the incoming or 'line' side of your main breaker with the breaker on and then off. With the breaker off the current will be essentially zero, so there should be no voltage drop between you and the utility transformer. Whatever he sees in this state is what the utility is supplying.

The measurement in the 'on' state should be similar, but may sag a few volts. If it sags a lot the service to your house may need attention. If the voltages into the main are OK in both states then you need to look at your house wiring.