Taming the Energy Demand Curve

Projections for growing demand for electricity – and the resulting energy infrastructure and environmental implications – continue to drive discussion of ways to avert calamity. One promising line of research is focusing on improvements to appliances that will reduce their overall footprint.

A new study by Washington, D.C.-based American Geophysical Union (AGU) raises the red flag on residential air conditioning demand. In “Implications of Increasing Household Air Conditioning Use Across the United States Under a Warming Climate,” AGU warns that the growing incidence of heat events accompanying likely global warming trends will increase air conditioning use and add to strain on the electricity grid and greenhouse gas emissions.

“Soaring temperatures and increased occurrence of heatwaves have drastically increased air-conditioning demand, a trend that will likely continue into the future,” the study abstract reads. “Yet, the impact of anthropogenic warming on household air conditioning is largely unaccounted for in the operation and planning of energy grids. We find substantial increases in future residential air conditioning demand across the U.S. — up to 8% with a range of 5% to 8.5% (13% with a range of 11% to 15%) after anthropogenic warming of 1.5°C (2.0°C) in global mean temperature.”

The study says soaring demand for air conditioning based on increased temperatures and other factors will require fixes that either somehow reduce reliance on mechanical cooling, decrease its energy usage (and thereby its climate impact), or expand grid capacity. The study seems to make a case for making big leaps in air conditioning equipment design and operation.

“Technological improvements in the efficiency of home air conditioning appliances could supply the additional cooling needed to achieve current comfort levels after 2.0° global temperature rise without increased demand for electricity,” the authors write.

A 2020 report by Rocky Mountain Institute, “Solving the Global Cooling Challenge: How to Counter the Climate Threat from Room Air Conditioners,” which focuses on the implications of a possible explosion in cooling demand in the developing world (Fig. 1), says there’s a clear path to improved cooling technology.

“The most advanced commercially available, vapor compression-based room air conditioners have achieved only about 14% of the theoretical efficiency limit; efforts to date have focused on meeting minimum performance standards and refrigerant transitions, and not transformative innovation in efficiency.”

Meanwhile, an appliance even more ubiquitous and indispensable, which demands a larger share of household energy  (Fig. 2) – the hot water heater – is getting more scrutiny. The growing push for dwelling electrification to lessen reliance on fossil fuels is helping to expand the market for water heaters that run on electricity instead of natural gas. While putting more load on the grid, electrically powered units – particularly emerging heat pump water heaters (HPWHs) – utilize technology that is improving their energy efficiency, giving them a possible net energy consumption/greenhouse gas emission advantage over gas units.   

The newest front in HPWH technology is the retrofit-ready 120V unit. The New Buildings Institute’s Advanced Water Heating Initiative (AWHI) is overseeing field tests of the units, which are seen as good candidates for gas unit replacements and a cost-effective alternative to 240V HPWHs that often require electrical service upgrades in structures with older electrical infrastructure. The energy efficiency promise of the HPHW is further enhanced with emerging communications technology that allows the units to be connected to the grid and become demand-response capable, and thus a potential asset to utilities as they navigate growing peak demand issues and add more renewables to their power generation fuel mix.         

Owen Howlett, research strategist at Sacramento (Calif.) Municipal Utility District., and a co-lead of a residential applications working group at AWHI, says heaters’ ability to store hot water gives them demand flexibility that’s attractive to utilities trying to manage loads. “As a thermal battery of sorts, they’re almost a perfect accessory for helping utilities to manage the grid,” he says.

Advances on both fronts – air conditioning units and hot water heaters – could play an important role in making the demand side of the energy equation an active participant in addressing a challenging energy and climate future. It’s similar in some “There’s hope that what we’re doing now with water heaters is the equivalent of that in terms of adoption,” he says. “There was worry initially that people wouldn’t accept that lighting, but they did because there was no sacrifice in performance. We need to make sure it’s the same with water heaters.”