The Atlanta-based ISP says it is drinking from the firehose in its efforts to win as many municipal Wi-Fi contracts in the US as possible, and is already thinking ahead to possibilities such as cross-geography and cross-provider roaming.

The fine points of the 10-year contract have yet to be worked out, but it is clear from the bids that EarthLink will be putting up most of the cash for the rollout. Google will provide some financial support for startup and operations. Motorola Inc will build it, with Tropos Networks kit.

Judging from the analysis of the bids, conducted by independent experts hired by the city, four-year-old Wi-Fi specialist MetroFi Inc came in a very close second, and it seems that Google’s financial muscle and close connection to San Francisco may have helped EarthLink seize the deal.

EarthLink and Google are financially stable companies, said EarthLink’s director of corporate communications Jerry Grasso. That’s one of the reasons the EarthLink deal was ultimately favored, he said. Google will shortly have about $11bn in the bank.

Google has said it will offer San Francisco residents 300Kbps Wi-Fi for free. It is believed it will support the service with location-based advertising. EarthLink will charge roughly $20 a month for 1Mbps connectivity. MetroFi had planned to offer that amount of bandwidth gratis.

The cost of building the network has not been disclosed, but Grasso said that the company expects to pay $10m to $15m to build out a similar service in Philadelphia, and $4m to $8m to build out service in Arlington, Virginia.

These were its two biggest wireless contract wins to date. Philadelphia’s population is about 1.5 million. Anaheim’s population is about 350,000, about half that of San Francisco.

EarthLink, which has its roots in the dialup ISP business, is also bidding for muni Wi-Fi deals in Minneapolis and in Portland, Oregon, according to Grasso.

Meanwhile, Google plans to rollout its own Wi-Fi in its home town of Mountain View, about an hour’s drive south of San Francisco. MetroFi has built networks in neighboring Silicon Valley towns Cupertino, Santa Clara and Sunnyvale.

While other ISPs will often be able to offer services over these physical networks, the question of roaming arises, and Grasso said that’s also on EarthLink’s mind.

If you paid $20 a month to EarthLink for dialup access, you’d better be able to get online in your hotel room no matter where you are, he said. The same will likely be true for Wi-Fi he said. He would not rule out the possibility of partnering with rival providers on roaming deals.