def te_exp_minus1(posy, nterm):
    """Taylor expansion of e^{posy} - 1

    Arguments
    ---------
    posy : gpkit.Posynomial
        Variable or expression to exponentiate
    nterm : int
        Number of non-constant terms in resulting Taylor expansion

    Returns
    -------
    gpkit.Posynomial
        Taylor expansion of e^{posy} - 1, carried to nterm terms
    """
    res = 0
    factorial_denom = 1
    for i in range(1, nterm + 1):
        factorial_denom *= i
        res += posy**i / factorial_denom
    return res