Re: GURPS Dungeon Fantasy Treasures 1: Glittering Prizes
 

I disagree. FP can be used for physical Extra Effort, and for long-distance travel such as h*king or swimming, and for the effects of various forms of deprivation such as food, sleep or hydration, as well as for powering most supernatural abilities (some may be Limied to ER only).

For this reason, ER is distinct from FP, although I agree with the reasoning of the RAW ruling for why ER shouldn't be cheaper than FP.

Re: GURPS Dungeon Fantasy Treasures 1: Glittering Prizes
 

The energy stored in Power Items is described as being FP that can only be used for spells, so I suppose in that regard it would be more appropriate to call it ER. As ER wasn't introduced into the DF line until DF3 while Power Items date to DF1, however, it started out being called FP, and continuing to call it such isn't really any more inaccurate than calling it ER (particularly as one can argue ER is just a special case of FP). It's ultimately just energy used to cast spells, regardless of if you refer to it as FP, ER, MP, energy, essence, or flombattery.

Re: GURPS Dungeon Fantasy Treasures 1: Glittering Prizes
 

From the description of Energy Reserve: "Each level of Energy Reserve (ER) gives 1 FP that you can only spend to cast spells of one type." It's an advantage that holds FP and applies special conditions to those FP; it doesn't establish a new, separate currency called "ER." When you spend energy points, they're FP whether you take them from your FP stat, your power item (which canonically "holds extra FP for casting spells"), or your ER. It's just that each source has different rules for how the FP it contains are spent, drained, and recharged. It's like comparing financial instruments: They might differ in how they're treated for the purpose of taxes, IRAs, offshore banking, etc. and have very different degrees of liquidity and portability, but they're all still measured in dollars, pounds, euros, or whatever, and can often be combined for specific purposes.