I found the release notes for xfce4-power-manager-1.3.1. I think it more likely that since I don't have upower 0.99 installed it does not work well with the upower-0.9.23-2.fc20.x86_64 I do have installed. I see on searching that Fedora 21 will get upower 0.99. I don't know if it will be made available for Fedora 20 also.
I found the release notes for xfce4-power- manager- 1.3.1. I think it more likely that since I don't have upower 0.99 installed it does not work well with the upower- 0.9.23- 2.fc20. x86_64 I do have installed. I see on searching that Fedora 21 will get upower 0.99. I don't know if it will be made available for Fedora 20 also.