What’s an air-to-water heat pump (AWHP)?
By
Trent Wolbe
Look, we’ve been saying it forever: Air-to-water heat pumps are amazing. Not only are they hyper-efficient in how they use and store energy to heat your water (and your home), but right now, they’re kind of all the rage because of the incentives that they bring.
Because there’s a lot of information out there, and it’s not always easy to digest, we thought it would be a good idea to explain a few things about air-to-water heat pumps in language that’s easy to understand. Hope it’s helpful. Spoiler alert: Harvest uses the most efficient air to water heat pump on the market, and Harvest is cheaper to install, with incentives, than most other HVAC options, especially those with air-to-water-heat pumps included.
What’s an air-to-water heat pump?
A heat pump is a device that moves heat around. For example: your refrigerator has a heat pump that moves heat from the inside of the fridge, to the outside. That makes it cold inside the fridge.
An air-to-water heat pump moves heat from air into water. Even when it’s cold out.
When we talk about “heat pump water heaters,” technically we’re referring to air-to-water heat pumps, but the difference is, they are devices designed to heat potable water, whereas typical air-to-water heat pumps heat non-potable water for heating, not for drinking or showering.
The difference is, generally, that a heat pump water heater refers to a product that heats water for domestic uses, whereas an air-to-water heat pump water for heating and cooling purposes.
Harvest, though, is not typical: we use a heat pump water heater as an air-to-water-heat pump for heating and for domestic hot water.
There are two main types of heat pump water heaters: integrated and split.
A popular model of integrated heat pump water heater is the Rheem ProTerra. The heat pump sits right on top of the water tank - it’s integrated into the water tank.
Split heat pump water heaters are just what they sound like: they separate the water storage from the heat pump itself.
What’s the most eco-friendly air-to-water heat pump?
The most eco-friendly air-to-water heat pump is the SANCO2. That’s because the most energy efficient air-to-water heat pump is the SANCO2. And efficiency = eco-friendliness. Because when you use less energy, you decrease the amount of fossil fuels needed to run the electrical grid. And when you use less fossil fuels, you reduce the amount of carbon pollution released into the environment - pollution that’s bad to breathe, and also causes long-term global heating.
Mind if we gush about some SANCO2 specs for a moment? It has the highest first-hour rating of any residential electric water heater, the highest real world efficiency (80% savings over electric resistance water heaters and 40%+ over an integrated heat pump water heater), and it uses the most environmentally-friendly refrigerant on the market: CO2, which is right there in the name.
Perhaps it won’t surprise you that a SANCO2 air-to-water heat pump is the engine of any Harvest system.
What rebates are available for air-to-water heat pumps?
A Federal 25C tax credit is available for up to $2,000, and a recently-launched TECH Clean California air-to-water heat pump (AWHP) program provides a $2,500 incentive for air-to-water heat pumps. For up-to-the-minute information about rebates available in your area, we suggest a home assessment through QuitCarbon (it actually works, and an actual human will work with you!), and/or using Rewiring America’s incentive calculator to learn more.
Harvest is eligible for a combined total of $11,500 incentive from TECH, which stacks $2,500 for air-to-water heat pumps, $7,500 for integrated hot water, and $1,500 for low-global warming potential (that’s Harvest too - and it’s unique to the industry).
Can an air-to-water heat pump do home heating and air conditioning?
Why yes, yes they can. Harvest uses an air-to-water heat pump to heat the water you use in your kitchen or shower, and uses the heat stored in the hot water tank to heat the rest of your home - and it’s available today. We use a regular air-to-air heat pump to cool your home.
Companies like ARIS Hydronics have begun working on air-to-water heat pump chillers that cool water. It’s awesome, but not widely-deployed yet. Expect to see a lot of innovations in air-to-water-to-air cooling in the next couple of years.
Does an air-to-water heat pump work with a mini split?
An air-to-water heat pump works fine in the same home as a mini-split, but it doesn’t really work together with a mini split.
A mini-split is a kind of air-to-air heat pump: the heat pump unit itself lives outside, and then the “head unit” (the thing that the cold air shoots out of) lives inside your room.
So: no problem to have both an air-to-water heat pump and a mini split in the same house, but they probably won’t be connected.
Harvest is an example of an integrated heating system with a split heat pump water heater: it replaces your gas-fired furnace with a water-fired furnace. Where’s that hot water come from? You guessed it: the SANCO2 split air-to-water heat pump.
Harvest works great with central HVAC, which is what most people already have installed in their homes - it really only requires one system for a home, whereas mini-splits usually require one system per room. That can get expensive, especially when you have a lot of rooms - and mini-splits usually don’t do a lot to heat or cool interstitial spaces like hallways and bathrooms.
What’s the difference between an air-to-water heat pump and other hot water systems?
An air-to-water heat pump is much more efficient than old-school resistive water heaters. Resistive water heaters are the equivalent of rubbing two sticks together to make fire: they take a lot of electrons and bump them up against one another, which works, but is super inefficient.
Air-to-water heat pumps are also way better than gas-powered hot water tanks or tankless systems, because, well, they don’t use gas - a non-renewable resource that heats the planet and causes nasty air pollution.
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Did that help? Hope so. Welcome to the future of water heating, where we can all massively reduce one of the largest sources of energy costs - and emissions - in our lives.
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