Solar for a Heat Pump: Sizing, Costs and Batteries in San Diego
Solar for a Heat Pump: Sizing, Costs and Batteries in San Diego
Yes, solar panels can power a heat pump, and in San Diego the pairing works especially well. A heat pump moves heat instead of making it, so it needs far less electricity than resistance heating, and a right-sized solar system can cover most or all of that load. What decides your savings is how the system is sized, when your heat pump runs, and whether you add a battery under California’s net billing rules.
TL;DR
- A heat pump runs on electricity, so rooftop solar is a natural match. Federal guidance says the pairing uses the renewable power for heating and cooling.
- Size solar for your whole home’s usage, heat pump included. Do not size it for the heat pump alone.
- Under California’s Net Billing Tariff, exported power earns less than you pay to buy it, so using solar on site (or storing it) matters most.
- A battery is not mandatory, but it often improves savings because heat pumps run in the evening and early morning.
- Roof direction, shade and roof age matter as much as the heat pump model.
Table of Contents
- Why solar and a heat pump fit together
- Can solar fully cover a heat pump?
- How much solar do you need to run a heat pump?
- NEM 3.0 and why batteries matter with a heat pump
- What it costs
- Improve the home before you size the system
- Our perspective
- Get a solar design built around your heat pump
- FAQ
- Sources
Why solar and a heat pump fit together
A heat pump is an electric appliance. It does not burn gas. The U.S. EPA explains that heat pumps use electricity to transfer heat rather than generate it, and says they typically use about half the energy of other electric home-heating sources. That efficiency is the reason the pairing makes sense: a smaller electric load is easier to cover with a rooftop system.
In San Diego County the math is friendlier than in most of the country. Mild winters mean heating demand is modest. Many homes have a heat pump or mini-split doing both jobs, with cooling in late summer and fall when the sun is strong. Solar production and cooling demand tend to rise together on hot afternoons.
The other half of the picture is your rate. SDG&E publishes a time-of-use plan, Schedule TOU-ELEC, for households with EVs, storage or electric heat pumps. Its rate table shows a wide spread between on-peak and super off-peak prices, which is exactly why when you use power matters as much as how much.
Can solar fully cover a heat pump?
It can on paper, over a year. In practice, whether it does depends on timing.
Think in two layers:
- Annual energy. Add up what the heat pump uses in a year and compare it to what your panels produce. A properly sized system can offset all of it, plus the rest of your home.
- Hourly match. Panels make power at midday. Heating peaks on cool mornings and evenings. Cooling peaks in the afternoon and evening. Power you cannot use at the moment you make it gets exported, and that export is credited at a lower rate than retail.
So “fully covered” usually means your annual production equals your annual use, with the grid or a battery handling the hours that do not line up. If a contractor promises a zero bill without talking about the hourly picture and your rate plan, ask more questions.
How much solar do you need to run a heat pump?
There is no universal number of panels for a heat pump, because heat pump electricity use varies with home size, insulation, equipment efficiency and climate. A peer-reviewed study of grid-tied solar with heat pumps in northern Michigan and southern Ontario found the pairing economically attractive in those conditions, but its system sizes are specific to that climate, those loads and those rates. It is not a sizing rule for San Diego.
Here is a better method.
Step 1: Get your real usage
Pull 12 months of kWh from your SDG&E bills or online account. If you are replacing a gas furnace or gas water heater, you are adding new electric load, so you need an estimate of that too. Ask your HVAC contractor for the expected annual kWh of the heat pump they are quoting, based on your home’s load calculation.
Step 2: Add the new load to your current usage
Your new target is current kWh plus expected heat pump kWh. If you also plan to add an EV, include it. An EV charger installation is often the next electrification project after a heat pump, and the charging load can be as large as the heat pump itself.
Step 3: Translate kWh into system size
The Department of Energy’s consumer guide says a 7-kW residential solar system produces roughly 20 to 35 kWh per day depending on climate. That is about 7,300 to 12,700 kWh a year.
Here is an illustrative example, not a quote. Say a home uses 9,000 kWh a year and a new heat pump adds 3,000 kWh. The target is 12,000 kWh. A system in the 7-kW range, in the upper part of that production band, would be in the right neighborhood. A real design uses your roof’s orientation, tilt and shading to refine this. Our guide to solar system output explains how kW, kWh and real-world production relate.
Step 4: Check the roof
The Department of Energy notes that panels typically perform best on south-facing roofs with slopes between 15 and 40 degrees, though other roofs can work, and that heavy shade or an aging roof can make a roof unsuitable. If your roof is near the end of its life, replace it first or at the same time. Our solar roofing packages put both jobs under one crew and one warranty, so you never remove panels later to redo the roof.
NEM 3.0 and why batteries matter with a heat pump
For new California interconnections since April 15, 2023, the CPUC says customers generally use the Net Billing Tariff. Under it, solar first serves your onsite load, and exported electricity is credited at a value-based rate that is usually lower than the retail rate. The older net metering tariffs are closed to new enrollments. This is what homeowners call NEM 3.0.
For a heat pump owner, this changes the strategy:
- Midday solar used directly by the heat pump is worth full retail value. Pre-cooling a house in the afternoon, or running a heat pump water heater at midday, uses power at its most valuable moment for you.
- Midday solar exported is worth less. That is the credit the CPUC describes as usually lower than retail.
- Evening and morning heat pump use is bought from the grid at higher time-of-use prices unless you have stored power.
The CPUC also notes that under the Net Billing Tariff, batteries can help maximize bill savings by letting customers use or export stored energy during high-value hours. With a heat pump, that means panels charge the battery by day and the battery runs the heat pump at night.
Do you need a battery?
Not necessarily. A battery makes the most sense when:
- Your heat pump runs mostly in the evening, early morning or overnight.
- You want backup power for outages, so heating, cooling and the fridge keep running.
- Your rate plan has a big gap between peak and off-peak prices.
A solar-only system can still make sense if you work from home, run cooling during the day, and can shift loads to midday. We design both ways and show you the numbers side by side. See our battery storage options for Tesla Powerwall, Enphase IQ and Franklin WH, and our breakdown of home battery payback with incentives.
Backup sizing needs care. Heat pumps have startup surges, and a compressor on a small battery can trip it. Our guide on matching kWh to kW for whole-home backup walks through how to choose.
What it costs
Our published ranges, from our own offer pages:
| Project | Published price range |
|---|---|
| Residential solar | $24,500 to $70,000 |
| Battery storage | $12,000 to $16,000 |
The wide solar range reflects system size, roof type, equipment and electrical work. For national context, the Department of Energy’s guide puts solar at about $3 per watt installed, so a 7,000-watt system is about $21,000 in that guide, which was published in 2022. San Diego pricing varies with the project, so use our ranges for your area. For specific battery numbers, see our Powerwall cost guide.
The heat pump itself is a separate purchase from your HVAC contractor. Ask them for its expected annual kWh, so your solar design accounts for it.
Incentives have changed
Older guides, including federal pages from 2022, describe a 30% tax credit for solar and storage through the 2032 tax year. That has since changed for homeowners who buy systems outright. We explain what happened, and why a prepaid lease can now be the stronger route, in our federal tax credit article. Our prepaid lease program is designed to save homeowners 30 to 40% on upfront costs. Check current rules with a tax professional before you decide.
How to estimate the heat pump’s effect on your bill
Use this quick routine:
- Take the heat pump’s expected annual kWh from your HVAC quote.
- Multiply by your average cost per kWh from your SDG&E bill. That is the cost to run it with no solar.
- Subtract the portion your solar will cover directly or through a battery.
- Compare with what you spend now on gas for heating and water heating, which the heat pump replaces.
If your bill jumps after installing a heat pump, the usual cause is that it runs during expensive peak hours on a plan that does not suit it. Checking rate plans such as TOU-ELEC, and shifting run times, often helps before you change anything else.
Improve the home before you size the system
Every kWh you do not use is a panel you do not have to buy. Before sizing, look at:
- Insulation and air sealing. Better envelopes shrink the heat pump you need. Even backyard studios and ADUs benefit from structural insulated panels that cut heating and cooling loads from the start.
- Roof reflectivity. A cool roof reduces cooling demand and works alongside solar.
- Duct leakage. Leaky ducts waste conditioned air, and a heat pump has to work harder to make up for it.
What about geothermal heat pumps? The Department of Energy observes that geothermal systems offer higher efficiency through stable ground temperatures but cost more up front. Most San Diego homes use air-source units, which suit our climate well and pair easily with rooftop solar.
Our perspective
After 30 years of installing solar in San Diego County, we see the same mistake again and again: homeowners size solar for the bill they have today and forget about the appliance they are about to add. A heat pump, an EV or both can add thousands of kWh a year. If the system is not designed for that, you end up buying power at peak rates anyway.
Our approach is to design one system for the whole electrified home. Our in-house engineers look at your roof, your usage and your goals, then model the heat pump load by the hour, not just the year. Under NEM 3.0, that hourly view is what decides whether a battery earns its place.
We also handle permitting, SDG&E interconnection and HOA approvals with our own crews, not subcontractors. If a new roof is on your list, we can do the roof and the panels together under one warranty. Heat pump, solar, battery and roof should work as one system, and one company should answer for it.
Curtis Williamson
Get a solar design built around your heat pump
If you are replacing a furnace or air conditioner, or you already own a heat pump and your SDG&E bill is climbing, talk to us before you finalize the solar size. We offer free consultations, a written project timeline before you commit, and transparent pricing. We design for your usage, your roof and your battery goals.
Start with our residential solar page, or contact us to review your bills and heat pump plans.
FAQ
Can a heat pump run on solar power?
Yes. A heat pump runs on electricity, and solar panels produce it. Federal and state guidance recommends pairing the two so renewable power handles heating and cooling. Your panels feed the home first, and any shortfall comes from the grid or a battery.
How many solar panels do I need for a heat pump?
It depends on the heat pump’s annual electricity use plus everything else in your home. Start with your annual kWh, add the heat pump’s expected kWh, then size a system to match, using your roof’s real production. A 7-kW system produces about 20 to 35 kWh a day, according to the Department of Energy, so many homes land in that range, but a design is the only way to be sure.
Do I need a battery with solar and a heat pump in California?
No, but it often helps. Under the Net Billing Tariff, exported solar earns less than retail, and batteries let you use stored energy during higher-value hours. If your heat pump runs mostly at night, or you want outage protection, a battery is worth modeling.
Is there a special SDG&E rate for heat pump owners?
Yes. SDG&E’s Schedule TOU-ELEC is a time-of-use residential plan for customers with EVs, storage or electric heat pumps. Compare it with your current plan using your hourly usage before switching.
Sources
- Heating & Cooling With Solar, NYS Clean Heat
- Heat Pumps, U.S. EPA
- Energy Saver Consumer Guide to Residential Renewable Energy, U.S. Department of Energy
- Homeowner’s Guide to Solar, U.S. Department of Energy
- Net Energy Metering and Net Billing, California Public Utilities Commission
- Economics of Grid-Tied Solar Photovoltaic Systems Coupled with Heat Pumps, MDPI Energies
- Schedule TOU-ELEC Total Rates Table, SDG&E
- Residential EV Charger Installation
- Smart Insulation for Backyard Builds