According to the solar power industry, a feed-in tariff is the most effective means of developing solar power. It is the same as a power purchase agreement, but is at a much higher rate. As the industry matures, it is reduced and becomes the same as a power purchase agreement. A feed-in tariff allows investors a guaranteed return on investment a requirement for development. A primary difference between a tax credit and a feed-in tariff is that the cost is borne the year of installation with a tax credit, and is spread out over many years with a feed-in tariff. In both cases the incentive cost is distributed over all consumers. This means that the initial cost is very low for a feed-in tariff and very high for a tax credit. In both cases the learning curve reduces the cost of installation, but is not a large contribution to growth, as grid parity is still always reached.