# Talk:Solar Photovoltaic Cells for the Kingston Home FAQ

The units for EPT don't make sense. First, in the numerator, MW (megawatts) is a unit of power (energy per unit time), not energy. Second, in the denominator, the units are energy MWh (megawatt-hours). The overall unit is thus 1/h; it should be a unit of time, not reciprocal time (which could be a unit of frequency). Confusion of units is common in the press; I hope someone who knows an accepted or "received" definition of EPT will correct this.--Egnatoff 13:02, 16 October 2009 (UTC)

Thank you for pointing out the typo. Based on my own experience reading LCAs and the convention used in the Alsema and Fthenakis paper cited in this article, I am confident units of energy (MWh) is the more appropriate unit of measurement. To use units of power (MW), you would need to first find the energy required to construct and maintain the technology (in MWh), and then average this out over the lifetime of the technology. This seems to be a very convoluted way of communicating energy payback. Anyway, to summarize the units should be in MWh.