I have a Weber S-670 natural gas grill. For the last couple of months, the grill will not heat up after dark, when temperatures are lower. During daylight hours and higher temperatures, the grill works fine. I have contacted my gas supplier and they maintain I have a malfunctioning grill, not low gas pressure. I have had two separate Weber repairmen check the grill, during daylight, and they tell me the grill works as it should. Not sure how to increase pressure to the grill during neighborhood heavy gas usage. Any suggestions appreciated.
As you can see from the image natural gas is supplied to commercial industrial and residential customers off the same line. I know it's a crude image but it's really how it works. If there was a significant pressure drop on a main branch of the system then commercial and industrial customers would be offline, resulting in Factory shutting down and other complications. Residential draw is the equivalent of taking a cup out of a swimming pool. That being said I would replace the regulator. I have been on the receiving end of some really nice barbeques because of faulty regulators. I actually have a bin of them right next to me as I write this. it's the one marked REGS it's an inexpensive repair. The only other thing I would look at is the gas line in your house. If it's undersized and your furnace or water heater starts you could experience pressure drop, resulting in a lazy flame.
Check also the maximum rate your gas meter can deliver and the maximum power of your grill. Remember that 1m^3/hr = 10kW, so if you have a G1,6 meter (1,6 m^3/hr) and your grill + furnace + water heater requiore 40kW you have to increase your service because current service is undersized.
A test you could do is turn off furnace and water heater then test your grill.
Another possible issue is the feed pipe being too thin (or very long): long (thin) pipe brings high head, if head is too high gas flow is restricted (to fix you need to run a bigger gas pipe to your BBQ). I suggest long run to be done with 22 pipe instead of thin 12.