For all battery-operated power equipment, “Voltage” can be considered the rating for “Power.” A 56-volt battery, for example, will provide more power than a 40-volt; however, there is more to consider when choosing a battery-powered tool system.
When considering "voltage" in terms of Power should not be the sole factor determining the "available power" a battery can provide. You should also consider the Amp Hours (Ah) of the battery system you are buying.
"Amp Hour x Volts = Watt Hour"
Overall, "power" when measuring battery equipment is measured in both; Amp-hours (Ah) and Battery Voltage (volts).
These two factors determine the available "Watt Hours" of any particular battery system.
For example, a 4 Ah lithium-ion battery will provide (stored) power – twice as long as a 2 Ah lithium-ion battery.
So a 40-volt - 4 Ah battery will produce about the same Watt-Hours as an 80-volt - 2 Ah battery. Therefore, it's more practical to compare overall Lithium-ion Battery Power – in terms of its "Watt Hours" over any other measurement.
Watt-hours are always listed on the battery label but may not be in the specs or box.
Our suggestion: Read the battery label on the models you're looking at, and use the Watt-Hours to compare one power tool vs. another. It's more reliable and quicker, and the formula is already done.