Substantial growth in US renewable-energy capacity will undoubtedly have a positive environmental impact.

But the reduction in carbon emissions renewable-energy advocates aim to achieve does not exclude potential benefits to consumers.

Because as renewable-energy generating capacity has expanded significantly over the last decade, household energy costs have decreased.

That's the conclusion reached in an energy-industry factbook (pdf) published by the Business Council for Sustainable Energy and Bloomberg New Energy Finance.

It showed, among other things, that household spending on energy has dropped to its lowest level as a share of total consumption since records began, in 1960.

The decline has come even as greenhouse gas emissions from energy have been falling over the past decade.

Energy consumption as a share of total household consumption expenditures averaged 3.9 percent in 2016, the first time it has dropped below 4.0 percent since records began, according to the factbook.

At the same time, the factbook's authors say greenhouse-gas emissions from the energy sector shrank 5.3 percent year-on-year in 2016, bringing them to 24.1 percent below 2005 levels.

Total US greenhouse-gas emissions fell to their lowest levels in 25 years last year, according to Bloomberg New Energy Finance.

Shifts in the energy-generation mix saw natural gas eclipse coal to become the largest source of US generating capacity, at 34 percent of the mix.

Coal fell to second place with 30 percent of the generating mix—its lowest share on record.

In comparison, coal's share in 2007 was 49 percent, while natural gas was at 22 percent.

Renewable energy increased from 8 percent to 15 percent of the energy-generating mix in the same period.

Over the last five years, renewable-energy projects have also represented 62 percent of US generating-capacity additions, according to Energy Information Administration and Bloomberg data.

The US is the second-largest global depository for renewable-energy investments, says Bloomberg.

In 2016, utility-scale photovoltaic solar installations reached 8.9 gigawatts, nearly doubling the previous record of 4.4 GW set in 2015.

Last year also saw 7.2 GW of coal-fired power plants retired. That figure does not include plants converted to natural gas or other fuels.

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The amount of coal generation capacity retired is important to consider, as it indicates whether new renewable capacity is actually displacing the carbon-intensive fuel, or supplementing it.

This story originally appeared on GreenCarReports.