Solar Offset: Why 100% Isn't Always the Goal
“Offset 100% of your bill” is a great slogan and a mediocre design rule. Here’s how to think about it.
Offset is the share of your annual electricity use your solar produces. 100% offset means your system makes roughly as many kWh in a year as you consume. It’s a fine target — but it isn’t automatically the right one.
Why 100% isn’t always optimal
- Roof limits. Your best (south/west) roof space may cap how much you can fit before you’re putting panels on poor orientations that produce little.
- Net-metering rules. Some utilities pay less for the surplus you export than you pay to buy power. Wildly overbuilding past 100% can mean banking credits at a poor rate. We size to your utility’s rules.
- Future load. Planning an EV or heat pump? It can make sense to over-build now so you don’t re-permit later.
How we pick a target
We start from your real annual usage, layer in your utility’s net-metering terms, account for shading and roof geometry, and factor known future loads. Often the sweet spot is somewhere between 80% and 110% — the number that gives you the best return, not the roundest slogan.
Frequently asked.
Should I size for my future EV now?
Often yes — adding capacity during the original install is cheaper than a second project and re-permit later.
Can I offset more than 100%?
Sometimes, but check how your utility credits surplus. Past a point, extra panels bank credits at a low rate and lengthen payback.
Have a question we haven't covered?
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