In a flood zone, an unanchored propane tank floats away
Start with the problem most Lowcountry homeowners never see coming. A propane tank is a large sealed steel vessel, and when floodwater rises around it, it behaves like a boat. In a Charleston-area AE or VE flood zone, an above-ground tank that is only partly full has enough empty volume to become buoyant, and surge or a king tide can lift it off its pad, drag it across the yard, and snap the gas line it was feeding. That is a documented failure mode after coastal storms, and it is the reason tank setup in the Lowcountry starts with the flood map, not the fuel spec.
Flood-zone rules here call for the tank to be anchored so it cannot float, which usually means strapping it to a poured concrete slab or a set of driven ground anchors sized to hold it down when submerged. On the lowest lots, downtown on the peninsula and on the barrier islands, the tank may instead need elevating above the base flood elevation on a raised platform, the same logic that lifts the generator itself. A licensed installer works this out against your specific flood zone before the tank is placed, because getting it wrong risks both a failed inspection and a genuine hazard during the next surge. If you want the two fuels compared feature by feature, the natural gas vs. propane guide does that. This page is about the setup work.
Sizing the tank for the outage you are actually planning for
Once anchoring and elevation are settled, tank size is the next decision, and it is really a runtime question. Propane gives you a fixed reserve of fuel: however many gallons are in the tank is exactly how long the generator can run before someone has to refill it. That trade matters most during the long, multi-day outages the Lowcountry is built to expect.
- A whole-home unit at partial load burns roughly a week or more through a 500-gallon tank, which is why that size dominates full-home backup here. The how long a standby generator will run guide walks the gallons-to-hours math.
- Smaller 100 or 250-gallon tanks cost less and take up less yard, but they need a refill sooner in a stretched outage. The right size depends on the generator’s output, how much of the house it carries, and how long area outages tend to run.
There is a Lowcountry-specific reason to size up rather than down. On the barrier islands and low peninsula blocks, a refill truck depends on a single bridge or connector staying open. When crews close those spans during and after a storm, a tank that ran low cannot be topped off until the road reopens. Sizing generously and filling ahead of a named storm treats the tank as the closed supply it becomes once the span shuts.
Dominion Energy natural gas, where the main reaches your street
For a large share of mainland and peninsula properties, Dominion Energy’s natural gas distribution already runs down the road, and that changes the calculation. A gas main is a low-maintenance choice day to day: nothing to fill, nothing to anchor against flood, and as long as the main holds pressure, nothing to run dry. When it is available, it is often the simpler path for Summerville and Goose Creek properties and much of the inner metro.
The catch is capacity. Tapping that line for a generator is more involved than it looks:
- Meter upsizing. A standard residential meter feeding an existing water heater and range can be maxed out the moment a generator is added. Dominion frequently has to upsize the meter or the service regulator before a large standby unit will run reliably, and that coordination is part of the job.
- Line sizing. A 22 kW generator at full load can call for roughly 280,000 to 350,000 BTU per hour, so the pipe has to carry that on top of everything already on the system.
- Distance and pressure. A long run from the meter to the generator pad often needs a larger diameter, or the unit starves at the far end.
Because of all that, a gas hookup is a permitted job for a licensed pro, not a weekend project. Where no Dominion main reaches, which is the whole story on the barrier islands and much of rural Mount Pleasant, Berkeley, and Dorchester, propane is not a fallback but the only option, and the anchoring and sizing above apply in full.
Salt air is corroding the fuel system the whole time
One last coastal reality runs underneath all of this. Salt air corrodes metal, so the tank shell, the regulator, the fittings, and the fuel line age faster near the water than inland. Corrosion-resistant hardware, proper coatings, and a placement out of constant salt spray extend the system’s life and raise the value of regular inspection, because a quietly corroding regulator is the kind of failure that only shows up when the generator is finally asked to run. Gas and tank work is permitted and inspected, and requirements shift by jurisdiction, so sizing, anchoring, and the permit get worked out for your address.
How fuel ties into the rest of the system
Fuel never stands alone. It has to match the generator and the switch, so it is spec’d as part of a full generator installation alongside the automatic transfer switch. On propane especially, ongoing maintenance earns its keep, since a tank that quietly runs low or a corroded regulator leaves a house dark at the worst possible moment.
Get matched with a licensed installer
Share your city and whether a Dominion gas main reaches your street or the property would need a propane tank, and a match follows with the one vetted, licensed local installer serving that area. Start from the home page whenever the details are ready.