Created using browser-solidity: Realtime Ethereum Contract Compiler and Runtime. Load this file by pasting this gists URL or ID at https://chriseth.github.io/browser-solidity/#version=soljson-latest.js&optimize=undefined&gist=

ApolloTrade

contract ApolloTrade {
    uint public kWh_rate = 1000;
    mapping (address => uint) energyAccount;
    mapping (address => uint) coinAccount;
    address public owner;
    
    function ApolloTrade() {
        owner = msg.sender;
    }
    
    modifier onlyOwner {
        if (msg.sender != owner) throw;
        _
    }
    
    function setRate(uint rate) onlyOwner {
        kWh_rate = rate;
    }

    // I am selling some energy; this will credit my account
    function sellEnergy(uint kwh) public {
        coinAccount[msg.sender] += (kwh * kWh_rate);
    }

    // I am buying some energy, thus crediting my energy account
    function buyEnergy(uint coin) {
        if (coinAccount[msg.sender] > coin) {
            coinAccount[msg.sender] -= coin;
            energyAccount[msg.sender] += (coin / kWh_rate);
        }
    }
    
    function getEnergyAccount() returns (uint kwh) {
        return energyAccount[msg.sender];
    }

    function getCoinAccount() returns (uint coin) {
        return coinAccount[msg.sender];
    }
}

throw has been deprecated.

instead, use this code block:

    modifier onlyOwner {
        // if (msg.sender != owner) throw;
        require(msg.sender != owner);
        _;
    }

// I am selling some energy; this will credit my account
function sellEnergy(uint kwh) public {
coinAccount[msg.sender] += (kwh * kWh_rate);
}

When the producer sells energy, his coin account will be deposited but I think his energy account has to be deducted also?