The Future of Heating has Arrived

Paul Ledman net zero heat pump powered home in Portland Maine

Video: Paul Ledman’s net-zero apartment building in Portland, Maine which uses 100% solar for heating and cooling and will never need fossil fuel inputs.

 

Say “Goodbye” to oil, propane, or natural gas for heat.  Lock in a cost for heating that’s less than $1.50/gallon oil equivalent, and dramatically reduce your home’s carbon pollution thanks to modern ductless, mini-split air source heat pumps (ASHPs).

Modern heat pumps are able to heat and cool 2-3x more efficiently than older electric technologies like baseboard and air conditioners, making them dramatically less expensive to operate than nearly every other form of heat, and the best air conditioner you can buy.

Best yet – by installing a solar electric array to power the electric consumption of the heat pumps, you are effectively heating your home with sunshine. Your solar array will generate credits in the summertime (when it is sunniest) which allow you to run the heat pumps in the wintertime (when it is coldest). Your system will effortlessly generate all the ‘fuel’ it ever needs from clean, abundant sunshine!

0-down, 2.99% financing is available through ReVision’s Own Your Power solar loan program.

Want to Heat for $1/gallon Oil Equivalent? Go Solar + Heat Pump

Heat pumps are less than half the cost to operate vs. the equivalent oil or propane system on a per BTU basis. This chart gives you a quick breakdown of relative costs.

Fuel Source Cost per Unit Cost per Million BTUs Cost to Heat Typical Home
Electric Baseboard $0.14 / kWh $44 $4,489
Heating Oil $3.70 / gallon $41 $3,938
Propane $2.50 / gallon $35 $3,404
Natural Gas $2.00 / therm $26 $2,587
Heat Pump $0.14 / kWh $18 $1,706
Heat Pump with Solar $0.09 / kWh $11 $1,023

Based on fuel data and pricing from: Maine Energy Office. Assumes typical oil boiler operating at 65% efficiency, propane and natural gas at 85% efficiency, resistive electric at 95% efficiency and heat pump at 250% efficiency (COP of 2.5). Solar PV kilowatt-hour cost of 8.5cents per kilowatt-hour based on typical pricing economics of a 4kw + system.

How Mini Split Heat Pumps Work

Air source heat pumps extract heat from the outside air using a reverse refrigeration cycle (imagine if you took a window air conditioner and flipped it around). By extracting heat from the the outside air and moving it inside, rather than directly heating the indoor air, the heat pump runs 2-3 times more efficiently than an electric baseboard heater. This is commonly referred to as a coefficient of performance (COP) of 2-3.

There are a number of different system designs, but the most common installation is a 1:1 ductless ‘mini split’ unit. This system design consists of an outdoor unit with heat exchanger and compressor, which does the actual heat extraction, and an indoor blower unit which blows warm (or cool) air directly into the home. Mini split means there is a 1:1 ratio – is one indoor unit for every outdoor unit. We also install ‘multi splits,’ (one outdoor unit to two or more interior units) and ducted units when appropriate to site specifics.

Heat Pumps are Great for Supplemental Heat for New and Existing Homes

Mitsubishi Air Source Heat Pump Exterior and Interior units

Exterior (above) and interior (below) units for a Mitsubishi air source heat pump installation in Greene, Maine.

Heat pumps are an excellent way to dramatically reduce the use of an oil or propane boiler in an existing home, without the need to fully replace the existing heating system. Heat pumps are used as supplemental heat, similar to the way wood or pellet stoves are – place it in a common area of your home and raise that area to a comfortable temperature. This allows you to lower your thermostat substantially, and rely on the efficient electric heat for most of your heating. The heat pumps will run very efficiently to temperatures as low as -15°F.

The simplicity and reliability of heat pumps also makes them a great choice for new homes, where the savings garnered by installing heat pumps instead of a traditional heating system can be used to install solar electricity for the home. By heating and cooling with electricity, and then using solar panels to generate electricity, you end up with a fully ‘net zero’ home!

We’re a Mitsubishi Electric Diamond Contractor

Mitsubishi Electric Diamond DealerReVision Energy carries the prestigious Diamond Contractor status with Mitsubishi Electric, meaning we can offer an industry-leading 12 year parts and compressor warranty on single-family, residential installation, and a 5 year parts and 7 year compressor warranty on multi-family and commercial installations.

ReVision is committed to technical excellent and our exacting engineering team feels that Mitsubishi Electric offers the best heat pump technology on the market. Specifically, we are impressed with their Hyper Heat low temperature performance and recent efficiency advancements in multi-split configurations.

Incentives

State incentives are periodically offered for heat pumps, currently:

Adding Solar = Ultimate Flexibility and Savings

Lincolnville Maine Community Library Solar Panels

The Lincolnville Library uses a solar PV system offset the electricity used to heat and cool the building with an air source heat pump.

Like all electric appliances, heat pumps are only as clean as the energy they consume. In Northern New England, this means a mix dominated by natural gas, coal, and nuclear electricity. Far better to clean up your act and run these units on sunshine!

A grid-tied solar electric array is an ideal partner for an air source heat pump. Net-metering agreements mean that your solar electric array can generate electricity whenever the solar resource is available. This means that your system will probably produce more electricity than you consume in the summertime, earning you a credit.

In the wintertime, when you need the electricity to heat your home with the heat pumps, you will run from power off the grid, but instead of being billed for it, you will benefit from the credits you earned while overproducing in the summer.

The overall result: solar banked in the summer used to heat your home in the winter! No other heating system allows you to generate your own fuel automatically.

What About Ground-Source Heat Pumps? (Geothermal)

Solar Geothermal System - Kennebunkport Maine

This solarized home in Kennebunkport, Maine uses solar PV panels to power a geothermal heating system. Also note the solar hot water collectors (gray rectangles) which very efficiently capture thermal heat for use making hot water.

Ground-source heat pumps (AKA geothermal) are also perfect partners with solar electric arrays – as ultimately, geothermal systems are a form of electric heat just like air source heat pumps. While they do run more efficiently (COP 4-5), the upfront costs of geothermal systems ($30,000 range) can make them cost-prohibitive. We can often quote multiple air source heat pumps AND solar for around the same project budget as a geothermal system.

Why use grid-tied solar for heating?

  • Affordability – Solar electric systems are more affordable than ever before, with great incentives andhistoric low pricing on photovoltaic panels. By choosing solar electric, you pre buy your fuel for the next 30-50yrs and insure yourself against future energy price increases.
  • Reliability – Whether you choose to power a ground-source (geothermal) or air source (mini split) heat pump with solar panels, you will have a long-lived energy solution. Solar electric panels are maintenance-free, warrantied for 25 years, and are expected to last 30+ years. We back all of our systems with 24/7 emergency service.
  • Convenience – Your PV system will be generating electric credits all summer long which can be used to heat your home in the winter. One ReVision employee put it this way – you can split and stack wood, OR you can go to the beach and let the sun do the work for you!

Space Heating with Solar Thermal

This home in Round Pond, Maine uses ground mounted 240 evacuated tube solar hot water collectors. This system produces more than 65,000,000 BTUs of clean, renewable heat energy per year for domestic hot water and space heating.

In the mid-2000s (when PV prices were roughly double what they are today) the more popular way to provide solar heat for a home was to integrate one of our solar hot water systems with traditional (boiler-fired) heating system.  Doing so is a technical achievement that only a few companies are able to do, as advanced controls and design are required for a successful installation.

We have roughly 50 systems of this style in the world, and while they work great, the Achilles heel with this method is that, by definition, heating is needed in wintertime when the solar resource is at its weakest.  On the days where heating is most needed, there is simply less (or no) sunshine available to harvest.  The corollary is that in the summertime, these systems will produce a huge abundance of hot water, which many homes will not have a productive use for.  The mis-match of energy need (winter) and energy availability (summer) result in an inherent inefficiency.  Where these systems are great are in the ‘shoulder’ seasons of spring/fall when there is a need for heat and a reasonable amount of sun available.

Company co-founder and engineer Fortunat Mueller wrote about our design process for Mother Earth News in 2011 and that article features much more in-depth information and practical advice that holds true today.

Another note is that this type of solar space heating requires low temperature distributed (e.g. radiant floor) heating, and are not compatible with most high temperature (baseboard) heating systems.  If you are looking for a true boiler replacement, consider a fully automated pellet boiler.