Define Your Goals
Before you look at a single spec sheet or product listing, answer these questions. Not all of them will apply to you, and some answers will be obvious. But working through them now — honestly — will save you from buying the wrong equipment, building the wrong system, or spending more than you need to.
Take your time here. This is the cheapest part of the entire process.
Goals & Motivation
Do you want to reduce your power bill?
This is the most common starting point, and it’s a good one. You’re paying the power company every month, and you’d rather pay less. Simple.
But “reduce my bill” can mean a lot of different things. Are you trying to cut it by 20%? 50%? Eliminate it entirely? Each of those is a very different system. A modest setup with a few panels and a small battery can meaningfully reduce your summer bills. Getting to 50% takes more panels, more storage, and more planning. Getting to zero — in Portland, with our winters — is essentially impossible without a massive investment and a willingness to change how you live.
Do you want backup power during an outage?
This is the other big motivator, and it’s fundamentally different from bill reduction. A backup system needs to deliver power on demand when the grid goes down — which means battery storage is non-negotiable, and the system needs to be wired to switch over when grid power disappears.
Think about what you actually need during an outage: the fridge, the freezer, a few lights, the internet router, phone charging, maybe the furnace fan. That’s a pretty modest load — probably 500—800 watts continuous.
If you were here during the Valentine’s Day 2021 ice storm and lost power for multiple days, you already know exactly why backup storage matters. That event jump-started a lot of people’s interest in solar, including mine.
Do you want to use less grid power during peak times?
If your utility offers time-of-use (TOU) rates — and PGE does — there’s money on the table. Peak rates are significantly higher than off-peak. A battery system lets you charge from solar (or from the grid at off-peak rates) and discharge during peak hours.
This is a “nice to have” for most DIY systems, not a primary design driver. But once you have the hardware, it’s essentially free money. Check your rate situation to see if TOU arbitrage makes sense for you.
Is this about saving money, resilience, or both?
Be honest with yourself here, because the answer affects how you evaluate your system later. If it’s purely financial, you’ll judge it by payback period and bill reduction. If it’s about resilience, you’ll judge it by how you feel during the next outage. If it’s both — which is most people — you need a system that does a reasonable job at both, which means you won’t fully optimize for either.
That’s fine. A system that saves you some money and keeps your fridge running during a storm is a good system.
Are you motivated by environmental reasons, or is this purely practical?
Either answer is fine, but it matters for one reason: if environmental impact is a strong motivator, you might be willing to accept a longer payback period. If it’s purely practical, the numbers need to work on their own merits. Know which camp you’re in so you can evaluate honestly.
Is there a specific event that triggered this?
A lot of people start thinking about solar after something happens — a big rate hike, a prolonged outage, a reminder about earthquake preparedness. That trigger often shapes what you think you want, but it might not be what you actually need.
If an outage triggered you, you’re thinking about backup power — but your daily bill reduction opportunity might be bigger. Just be aware of your trigger so it doesn’t narrow your thinking too much.
What You Want to Power
Power specific circuits, or as much of the house as possible?
This is one of the most important decisions you’ll make, and it directly drives your system size and cost.
Many DIY systems don’t power the whole house. They power selected circuits — you choose which circuits run off solar/battery and which stay on the grid. You might put your fridge, freezer, furnace, a few light circuits, and your internet on the solar side. The rest of the house stays on grid power.
There’s a huge advantage to this approach: you don’t need a system big enough for everything. You need a system just big enough for the things that matter. A 3—5 kW system can comfortably cover essentials. An entire house might require 10+ kW and a much bigger battery bank.
Start by listing the circuits you’d want on solar. Walk to your breaker panel, read the labels, and think about what you’d want running if the grid went down. That list is your starting point.
What are your must-haves vs. your nice-to-haves during an outage?
Do you have any 240V loads you want to cover?
Most large appliances — clothes dryers, electric ovens, well pumps, central AC, mini-splits, EV chargers — run on 240 volts. A 120V system can’t power them.
If you want to cover 240V loads, you need a 240V-capable inverter, which costs more and adds complexity. See the inverters page for what that actually means.
If you have a specific 240V load that’s a dealbreaker — a well pump, a medical device, a mini-split that’s your only cooling — plan for 240V from the start. Retrofitting from 120V to 240V later is expensive and painful.
Do you have any always-on loads?
These are sneaky. A gaming PC that’s always on might draw 150 watts around the clock — that’s 3.6 kWh per day from one device. A home server, an aquarium heater, a second fridge in the garage — they all add up.
Always-on loads are important for two reasons: they inflate your daily consumption and therefore your system sizing, and they drain your battery overnight even while you sleep. Find them before you size anything. A Kill-A-Watt meter is your best friend here.
Is your daily offset goal different from your outage goal?
It might be. Day-to-day, you might want to offset as much of your bill as possible. During an outage, you’d be happy with just the essentials.
Your system can handle both scenarios. A 10-circuit transfer switch gives you the flexibility to have some circuits running off solar all the time and others you’d only switch over during an outage.
Time & Season
Is this for year-round daily use, or primarily summer months?
Solar production is heavily seasonal. June might produce ten times what December does. If you’re designing for year-round impact, you need to accept that winter performance will be modest. If you’re designing primarily for summer — when the sun is strong and electricity is expensive — you can build a smaller system that performs beautifully for six months and contributes less the other six.
Neither answer is wrong, but they lead to different system designs.
Are you okay with the system doing very little in winter?
You need to be, at least to some degree. December in Portland averages around 1—2 peak sun hours. June averages 5—6. Your panels don’t stop working in winter, but they produce a fraction of what they do in summer.
The better answer is usually: design for the productive months, accept the winter dip, and use the battery for TOU arbitrage and outage backup during the dark months. Check PVWatts for production estimates specific to your location.
How important is overnight coverage?
If you only care about generating power while the sun is shining, you technically don’t even need a battery. But most people want overnight coverage — for outage protection and to avoid buying expensive evening peak power.
A rough rule: figure out your overnight load in watts, multiply by the hours you want covered. A 500-watt overnight load for 10 hours is 5 kWh of battery minimum.
Is time-of-use gaming a priority?
If your utility has TOU rates, your battery can charge at cheap off-peak prices and discharge during expensive peak hours. You don’t need to set this up on day one — but make sure the inverter you choose supports programmable charging schedules. The hardware decision is now; the configuration can come later.
How It Works
Do you want automatic or manual switchover when the grid goes out?
An automatic transfer switch detects when grid power drops and switches your circuits to battery power in seconds. A manual transfer switch requires you to physically flip a switch.
If you have medical equipment that can’t tolerate any interruption, automatic is worth the cost. If you’re mostly home and can walk to the panel in two minutes, manual is fine.
How much do you want to monitor and manage vs. set-and-forget?
Some people want to watch their system like a dashboard. Some people want to flip the switch and forget it exists until the power goes out. Both are valid.
At minimum, get a system that gives you battery state of charge at a glance. You should always know roughly how full your batteries are.
Do you want to check it from your phone?
Remote monitoring is genuinely useful if you travel or just want peace of mind. Most smart inverters can send notifications if something goes wrong. Even a set-and-forget person wants to know if their battery stopped charging.
Physical Setup
Roof mount or ground mount?
Roof mounting is the most common approach — it’s out of the way and doesn’t take up yard space. Ground mounting is easier to install, easier to maintain, and easier to adjust. Some people do both — start on a shed or ground rack and add roof panels later.
Do you have south-facing exposure?
South-facing is ideal in the northern hemisphere. But east- or west-facing panels still produce roughly 80% of what south-facing panels do. Partial shade is trickier — a shadow across even part of a panel can significantly reduce output for the whole string.
The best test is free: go outside on a sunny day and watch where the shadows fall at different times.
Where would the battery and inverter live?
Your inverter and batteries need a home — somewhere protected from weather, with reasonable temperature control, and accessible for maintenance. Garage, basement, or utility room are common. Temperature matters for LiFePO4 batteries: they don’t like charging below freezing.
How far is the panel location from your equipment?
Wire runs matter more than you might expect. A 20-foot run is easy. A 100-foot run requires careful wire sizing and voltage drop calculations. Where panels go and where equipment lives should be decided together.
Do you have an accessible breaker panel?
Your transfer switch connects to your main breaker panel. Check if your panel is in an accessible location and whether it has open slots. A photo of it with the cover off is useful reference material.
Budget & Scale
Do you want to spend a little or a lot?
There’s a workable DIY system at almost every budget level. A few hundred dollars gets you a portable panel and small power station — enough to learn and charge devices. A few thousand gets you a real system that powers essential circuits. $5,000—$9,000 gets you something that makes a serious dent in your bill and provides solid backup.
See the System 1 (200W starter build) and System 2 (3.2kW permitted system) as concrete budget anchors.
Are you building a starter system you’ll expand, or build it once?
Some things are easy to add later — more battery capacity, additional panels. Some are hard to change — the inverter, the transfer switch, wire gauge, mounting infrastructure.
If you think you’ll expand, invest in the infrastructure now. Get the 10-circuit transfer switch even if you’re only using 6. The marginal cost of planning bigger upfront is tiny compared to retrofitting later.
Is there a hard budget ceiling?
If you have a fixed number, design to it. If you’re flexible, that gives you more options. Know your number and be honest about it.
Spend more upfront, or start minimal and expand?
Buying everything at once is usually cheaper per component. Building incrementally lets you learn as you go and spread the cost out. Just make sure your small system is designed with expansion in mind.
You & Your Situation
Are you doing this alone or do you have a partner?
You can absolutely do this solo. But having a partner — even someone who just holds the other end of a panel — makes the physical work faster and safer. Explaining your wiring plan to another person is one of the best ways to find mistakes before they matter.
What’s your comfort level with electrical work?
Be honest. There’s a range:
- Never touched a breaker panel: You can still do this. Plan for a steeper learning curve and extra research. Consider having an electrician friend check your work before you energize anything.
- Changed outlets, wired a light switch: You have the fundamentals. Solar wiring is a step beyond, but the principles are the same.
- Wired a subpanel, comfortable with a multimeter: You’re well-equipped. The solar-specific stuff will be new, but the core skills transfer directly.
Whatever your level, respect the electricity. DC from solar panels can’t be switched off while the sun is shining. Battery banks store serious energy. Double-check connections and never work on a live circuit if you can avoid it.
Do you own or rent?
If you own, you have full control. If you rent, your options are limited but not zero — a portable panel and power station can work on a balcony or patio. Some renters have a conversation with their landlord about a non-penetrating system. The worst they can say is no.
Are you planning to stay in this home long-term?
If you’re planning to move in a year or two, a permanent rooftop installation is harder to justify. If you’re staying five-plus years, the payback math works in your favor. If you’re somewhere in between, consider a system designed to be removable.
Does anyone in your household have medical equipment that needs uninterrupted power?
What’s Next
Now that you know what you want, let’s figure out what you actually use. Know Your Numbers walks you through measuring your real consumption — the foundation for sizing everything else.
DATA SOURCED FROM: Section-01-Define-Goals source document (primary). Production seasonal estimates based on PVWatts data for Portland, OR (NREL). System sizing rules of thumb from source material.