is stored at high pressure, . The required tank is more massive and costly than a conventional fuel tank. Commercial on-demand refueling stations are more expensive to operate than LNG stations because of the energy required for compression; the compressor requires 100 times more electrical power. However, slow-fill (many hours) can be cost-effective with LNG stations [missing citation - the initial liquefaction of natural gas by cooling requires more energy than gas compression]. The time to fill a CNG tank varies greatly depending on the station. Home refuels typically fill at about 1 kg/h (0.4 GGE/h). At gas stations, where the pressure is greatly higher, it is possible to refill a 25 kg (10 GGE) tank in 5–10 minutes. Also, because of the lower energy density, the CNG range is lower compared to LNG. Gas composition and throughput allowing, it should be feasible to connect commercial CNG fueling stations to city gas networks or enable home fueling of CNG vehicles directly using a gas compressor. Similar to a car battery, the CNG tank of a car could double as a home energy storage device, and the compressor could be powered at times when there is excess/ free renewable electrical energy. LNG as an auto fuel LNG, or liquified natural gas, is natural gas that has been cooled to the point that it is a cryogenic liquid. Its liquid state is still more than twice as dense as CNG. LNG is either dispensed from bulk storage tanks or made locally from utility pipes at LNG fuel stations. Because of its cryogenic nature, it is stored in specially designed insulated tanks. Generally speaking, these tanks operate at fairly low pressures (about ) when compared to CNG. A vaporizer is mounted in the fuel system, turning the LNG into a gas (which may be considered low-pressure CNG). When comparing a commercial LNG station with a CNG station, utility infrastructure, capital cost, and electricity heavily favor LNG over CNG, but the availability of piped gas is more common than LNG delivery by tanker. There are existing LCNG stations (CNG and LNG), where fuel is stored as LNG, then vaporized to CNG on-demand. LCNG stations require less capital cost than fast-fill CNG stations alone but more than LNG stations. Aside from different fuel tanks, fuel metering and computer modules, the engines in NG vehicles could be run by CNG or LNG without requiring any modification