Party Walls

Air-source heat pumps are a booming business. In the Northeast, manufacturers report that sales of residential systems have increased by 25-35% per year over the past 5-10 years. We’ve seen more and more systems being installed in existing homes (to provide cooling while offsetting oil or propane used for heating) and into new homes (often as the sole source of heating and cooling).

We’ve looked into these systems often, and from many perspectives. I’m planning a series of posts, but, for now, here are the answers to some basic questions we receive from clients.

First, the basics: What is an air-source heat pump (ASHP)?

It’s an air conditioner that can operate in reverse. During the summer, it moves heat from indoors to outdoors. In the winter, it moves heat from outdoors to indoors. We helped NEEP (the Northeast Energy Efficiency Partnerships) to put together a market assessment and strategy report on ASHPs. The early sections in this document (see p. 12) outline the different terms and types of heat pumps (ducted/ductless, split/packaged, mini-split, multi-split, central, etc.) Unfortunately, different people can use the same term to mean different things, but hopefully the NEEP Northeast/Mid-Atlantic Air-Source Heat Pump Strategies Report can help clarify things.

Indoor section of heat pump.

Outdoor section of a heat pump.

(more…)

Ten years ago, seeing a solar electric system on a building was noteworthy. Now they’re popping up everywhere. Lower cost is obviously a big driver of this solar surge; photovoltaic (or PV) system costs have dropped 50-70% in the past 10-15 years. Over the past decade, SWA has helped developers and owners install PV systems on hundreds of buildings. The systems are reliable, they have no moving parts, and they will convert sunlight to electricity for decades.

The cost effectiveness of PV, however, is not always clear. In fact, SWA has seen a concerning trend where the cost benefits of PV are exaggerated. Although costs vary with region and application, installed costs of PV are usually $3,000 – $6,000 per kWSTC.

Then there are incentives, including two key federal programs:

• 30% Federal tax credit
• Accelerated depreciation (for businesses)

Other incentives vary greatly from region to region:

• State, local, and utility rebates or credits
• Sale of Renewable Energy Credits (RECs)

The Database for State Incentives for Renewable Energy (dsireusa.org) has a good summary of these regional incentives. Federal and regional incentives can easily lower PV system costs by 50% — often more.

The final piece in assessing cost effectiveness of PV is the electricity savings. With PV generating electricity for your building, you’ll obviously be paying less to the utility. But how much less? (more…)