There is a challenge in retrofitting energy efficient LED’s into the G9 form factor because the halogen capsules are physically so small. Because of this the majority of bulbs on the market are ether very low powered or physically huge, too big for most light fittings.
My goal has been to cut the energy usage of two halogen G9 fittings. The net consumption of the pair being 80w. The best substitute halogen G9 bulb I am aware of is the LED COB G9 bulb which may be found in 5W and 7.5W. They have good light production and color balance. As of writing they are still quite expensive and must be sourced online. If you’re going to substitute G9 capsules it is worthwhile spending a bit extra on these, or giving the market time to mature. Cheap low powered bulbs will disappoint.
My first test was a 1.5W by Long Life Lamp Co, representative of most G9 substitutes. This bulb is dim and near useless for general room lighting. LED G9 bulbs less than 2w are near useless for room lighting unless used in great numbers. Such bulbs may find application in night lights or feature lights. The only way you’d practically use these in general lighting would be combining them with halogens which rather defeats the purpose.
As of writing I am using the two in parallel, with the 5W COB as the primary and the little 1.5W filling in on the other side of the beam. This uses a total of 6.5W.