Here we see prices of electricity quoted in units of $/(megawatt hour) and natural gas in units of $/MMBtu.
According to the MMBtu reference 3412 BTUs = kWh and MMBTU = 106Btu. I get .0034 MMBTU = kWh.
PG&E Tarrifs, too

Watt = joule/sec, kWh = 3,600,000 joules = 3.6 106 joules.

In particular on 2008 Dec 15 I see roughly $6/MMBtu for natural gas and $70/(megawatt hour) for electricity. At that price my kW electric heater costs about $0.07 per hour. The same energy by gas is ($6/MMBTU)*.0034 MMBTU = $.018 Running my gas furnace heats my room in a similar period and heats the rest of the house to a much lesser extent. I need to read my gas meter twice when the furnace is running.

On 2009 Mar 26 I see prices gas: $4/MMBtu, Elec: $30/Mwh. (20H GMT)

It takes 34 sec for one complete rotation of ‘half foot’ dial which is subdivided by 10 equally spaced marks.

Implicit in this patent is that a two-foot dial does one rotation (total range) for two cubic feet of gas. From this I assume that I consume 34/30 = 1.1 CuFeet per minute.

My PG&E bill speaks of Therms each of which seems to be very near one unit of meter reading. I suppose that therm = 105 BTU = 1.055 108 joules.

It seems from my PG&E bill that a meter unit is 100 ft3 which yields 1.0165 Therms. The ‘Baseline’ rate, which I pay, is $1.069/Therm in Nov 2008. That these two numbers are very near one seems indeed to be a coincidence.

On 2008 Dec 31 Russia asks $250/103m3 of Ukraine for gas.
m3 = 35 ft3
price = $0.007/ft3.
stuffsold unitin joules$/unit
electricitykWh 3.6 1060.115
gastherm 1.055 1081