Key takeaway
The production estimate is how many kWh your panels should make in a year. In Massachusetts, a realistic estimate usually works out to about 1.1 to 1.2 kWh for every watt of solar. Divide the estimate by the system size in watts to check yours. If it's well above that range, ask how they got it.
Who this guide is for: Massachusetts homeowners looking at the production number on a solar quote and wondering if it's realistic.
The production estimate is the most important number on your solar quote. Your offset, your savings and your monthly bill are all built on it. If it's too optimistic, everything else on the page is too.
Here's what the number means, what goes into it, and a quick Massachusetts check to see if yours holds up.
At a glance
| What it is | Estimated kWh your system makes in its first year |
| MA benchmark | About 1.1 to 1.2 kWh per watt of solar per year |
| Quick check | Yearly kWh ÷ system size in watts |
| Biggest factors | Roof direction, tilt, shade and weather |
| Compare to | Your last 12 months of kWh usage |
What does the production estimate on my solar quote mean?
It's the number of kilowatt-hours (kWh) your system is expected to make in a year. It's usually shown as a yearly total, often with a month-by-month chart.
Don't confuse it with system size. System size, in kW, is how big the system is. Production, in kWh, is how much electricity it makes. An 8 kW system in Massachusetts might make about 9,200 kWh a year.
Is my solar production estimate realistic?
Here's the quickest check there is. Divide the yearly production estimate by the system size in watts.
Example: 9,200 kWh ÷ 8,000 watts = 1.15.
| Your ratio | What it usually means in Massachusetts |
|---|---|
| Below 1.0 | Lots of shade or a tough roof direction. Ask if the design can improve. |
| 1.0 to 1.2 | Normal range for most Massachusetts homes |
| Well above 1.2 | Worth asking how they got it |
Massachusetts systems typically make about 1,100 to 1,200 kWh per kW per year.
A high ratio isn't automatically wrong. A big south-facing roof with no shade can do very well. But if the number looks high, ask the company to show you how they calculated it.
What goes into a solar production estimate?
- Direction: south-facing roofs make the most. East and west roofs make less.
- Tilt: the pitch of your roof changes how directly the sun hits the panels.
- Shade: trees, chimneys and nearby buildings. In Massachusetts, mature trees are the big one.
- Weather: years of local sun and weather data for your area.
- Equipment and losses: panel output, inverter type and small losses from wiring and heat.
A good estimate uses your actual address and roof. Ask whether it came from a site visit, a shade report or design software for your specific home.
Not sure your production estimate is realistic?
Send your quote to Mark. He'll check the numbers against your roof and your usage.
Mark, review my quoteWhy do two quotes show different production for the same size?
It happens all the time. Two companies quote the same 8 kW system, and one shows 1,000 kWh more per year.
The difference usually comes from different design tools, shade data or assumptions. Run the ratio check on both. If one is much higher, ask both companies how they got their number. It's one of the first things to look at when you compare two solar quotes.
How to check the estimate yourself
You can run your own estimate with PVWatts, an online tool from the National Renewable Energy Laboratory that anyone can use. Enter your address, the system size, the direction your roof faces and the tilt. It gives you a yearly kWh estimate to compare with your quote.
PVWatts doesn't know about your trees, so treat it as a rough check, not a final answer.
What about snow and winter months?
A good estimate already includes normal Massachusetts weather, including snow and short winter days. Your monthly chart should show much lower production in December and January and much higher in spring and summer.
Snow usually slides off panels within a day or two, so solar panels work in the snow better than most people expect.
How does production compare to my usage?
Divide the yearly production by your yearly usage from your bills. That's your offset. About 90% to 110% is a good fit for most homes. If you're not sure your system is the right size, here's how many solar panels you need.
What if my system makes less than the estimate?
Watch your monitoring app for the first full year. One cloudy month doesn't mean anything is wrong.
If production stays low for months, look for new shade, snow that isn't clearing or an error message in the app. Then call the company you signed with and ask them to take a look.
The production estimate is one of five sections to check when you read a solar quote from top to bottom.
Got a solar quote?
Send it to Mark. He'll go through it line by line and tell you if it's a good deal for your home.
Mark, review my quoteFAQs About Solar Production Estimates
What is a good production ratio for solar in Massachusetts?
In Massachusetts, a typical production ratio is about 1.1 to 1.2. That means each watt of solar makes about 1.1 to 1.2 kWh a year. A ratio well above that is worth asking about.
How accurate are solar production estimates?
A good estimate based on your actual roof and shade is usually close over a full year. Weather changes from year to year, so a single year can come in a bit higher or lower.
Why do two solar quotes show different production for the same size system?
Different companies use different design tools, shade data and assumptions. Divide each estimate by its system size in watts. If one ratio is much higher than the other, ask how they got it.
Why is my solar producing less than the estimate?
Common reasons are a cloudy stretch, snow cover, new shade from growing trees or an equipment issue. Check your monitoring app and compare a full year, not one month. If it stays low, call the company you signed with.
About Mark Featherstone
Mark has been in solar for 14+ years, working at some of the biggest solar companies in the country, before co-founding Your World Solutions. His goal is simple: help homeowners get into solar deals that actually work for them, and make sure they understand every part of it before they sign.
This article is for general informational purposes only and isn't legal or tax advice. Every home, quote and contract is different, and production, savings, timelines and program rules vary and can change. Read your own contract carefully and talk with a qualified professional before making a decision.