Before making any big buying decision it is only natural to want to understand the options. To do this we need to be able to make sense of the home heating systems ratings. They are not complicated, luckily, but they are a bit like a new language when you first see them.
One of the problems is that different ratings are used for furnaces that burn fuel (gas central heating boilers, oil, wood etc) and those that use electricity. This is a familiar problem - it is always hard to compare electricity efficiency with other things because the electricity needs to be produced before it reaches the consumer. These electricity producing costs are handed down to the user.
So a system like a heat pump or blown air heater, which uses electricity will be rated by something known as HSPF - Heating Seasonal Performance Factor. You are looking for bigger factors (even approaching 10) here. It is a measure of how much heat each electrical piece of energy produces - 10 would mean that each electrical energy unit is turned into ten heat energy units using a heat pump.
The larger numbers mean greater efficiency and less energy used for heating. These figures will have been gathered in certain conditions that may not be like yours however, so if you buy a heat pump with a HSPF of 9, it might not perform like that in a real setting.
Home heating furnaces on the other hand are rated by AFUE - Annual Fuel Utilization Efficiency. It is a measure of efficiency plain and simple. If it is 90% that means that nine tenths of the heat produced by burning the raw fuel is used for heating purposes - you are looking for numbers above 85 or 90%.