What Size Solar Generator Do I Need? (Free Sizing Tool)
By Keith Baxter - Last updated: October 15, 2026
"What size solar generator do I need" is the right first question, and the one most people answer backwards: they buy the battery first and the appliances second. Size is two separate numbers, and people searching "solar generator how many watts" usually mean both. This page's calculator computes them from your actual appliances, and the written method below explains what to look for when buying a solar generator so you can sanity-check any product page. For baseline appliance wattages, the Department of Energy's appliance energy guide is the reference we start from, and Ready.gov's power outage guidance frames the emergency-planning side of sizing.
$2,497.00$2,997.00
Price as of October 15, 2026 - check current price
- FREE 200W solar panel included (per merchant, $447 value)
- Ships from US warehouses, typically same day
- Arrives in 2-3 days (per merchant)
- 3,500+ cycle LiFePO4 battery
Merchant trust points are as reported by the merchant.
The Sizing Calculator
Check your appliances, adjust the watts to match their labels, and read your three numbers: running watts, surge need, and watt-hours per day.
1. Pick your must-run appliances
Default watts are rough estimates. Edit them to match your appliance labels.
Your result
- Running watts (simultaneous)
- 235W
- Estimated surge need
- 2,635W
- Energy per day
- 1,995Wh
Recommendation: Grid Doctor 3300
Fridge-class and kitchen loads need the 3,300W inverter, 6,600W surge and 2,048Wh battery (expandable to 16,384Wh). This covers your selection with headroom.
Worked Examples (Same Math, Server-Rendered)
| Scenario | Running | Surge est. | Wh/day est. | Size pick |
|---|---|---|---|---|
| Phones, lights, router only | ~85W | ~85W | ~300Wh | Grid Doctor 300 class |
| Fridge + lights + router | ~210W | ~2,610W | ~1,600Wh/day | Grid Doctor 3300 |
| Fridge + furnace blower + lights + router | ~710W | ~3,110W | ~5,200Wh/day | Grid Doctor 3300 + expansion batteries |
Estimates use typical residential appliance draws; your labels win. The calculator above uses the same arithmetic with your numbers.
$2,497.00$2,997.00
Price as of October 15, 2026 - check current price
Merchant trust points are as reported by the merchant.
What to Look for When Buying a Solar Generator
- Inverter output vs your running watts. Your simultaneous load must fit under the continuous rating, with the surge rating comfortably above your biggest compressor. The Grid Doctor 3300's 3,300W/6,600W figures exist for exactly the fridge-plus-kitchen scenario.
- Battery chemistry and cycles. LiFePO4 with a published cycle rating (3,500+ on the 3300, per manufacturer) is the long-game choice; our LiFePO4 vs lithium-ion guide explains why.
- Recharge inputs. Wall, solar and car charging plus pass-through. The 3300 takes 1,800W AC quick charge and up to 1,000W solar (per manufacturer).
- Expandability. Starting right-sized is only possible if the platform grows: the 3300 accepts up to 7 expansion batteries (2,048Wh each).
- Resilience extras. UPS switchover (~15 ms on the 3300, per manufacturer) and, uniquely, built-in EMP protection (manufacturer claim, 3 ns reaction, independently tested).
Your Recommendation, in Plain Terms
If the calculator says fridge, furnace blower or kitchen appliances, buy the 3,300W class: the Grid Doctor 3300 EMP Solar Generator at $2,497.00 (compare-at $2,997.00, verified October 15, 2026) with its free 200W panel is our top pick in that class, and expansion batteries let you scale instead of replacing.
$2,497.00$2,997.00
Price as of October 15, 2026 - check current price
- FREE 200W solar panel included (per merchant, $447 value)
- Ships from US warehouses, typically same day
- Arrives in 2-3 days (per merchant)
- 3,500+ cycle LiFePO4 battery
Merchant trust points are as reported by the merchant.
If your selection stayed light-duty (phones, lights, router, laptop), you genuinely do not need 3,300 watts. The compact Grid Doctor 300 class does the same quiet, indoor-safe job at a fraction of the size:
Frequently Asked Questions
What size solar generator do I need to run a refrigerator?
Plan for an inverter with strong surge headroom and roughly 2,000Wh of storage. A typical fridge averages around 100W while cycling, so 2,048Wh runs it about 20 hours per charge, and the startup spike is covered by a 6,600W surge. The full fridge math is in our refrigerator guide.
How many watts does a solar generator need to run a house?
For appliance-level backup (fridge, furnace blower, lights, devices, kitchen loads), 3,000W-class continuous output with a large surge covers most households. Whole-home power including 240V HVAC is beyond any portable 120V unit and requires a standby generator with a transfer switch.
What is the difference between running watts and surge watts?
Running watts are what your appliances draw continuously; surge watts are the brief spike when motors and compressors start, often double the running draw. Your inverter's continuous rating must exceed the first number and its surge rating must exceed the second, or the appliance will not start.
How do I calculate watt-hours per day?
Multiply each appliance's running watts by the hours it runs per day, then add everything up. For cycling appliances like fridges, use average draw (a fraction of nameplate watts) times 24 hours. The calculator on this page does this for you with editable defaults.
Is a 300W solar generator enough?
For phones, tablets, LED lights, a router and a laptop, yes, and it costs far less. It cannot run kitchen appliances or a furnace blower, which is why the Grid Doctor 300 and the Grid Doctor 3300 exist as two different tiers rather than one product.
Should I buy a bigger generator than I need?
Buy surge headroom, not idle capacity: a bigger inverter handles startup spikes and future loads, while extra battery capacity you never cycle is money sitting in a closet. The smart middle path is a right-sized unit on an expandable platform, like the 3300's 16,384Wh ceiling.
Does a bigger generator cost more to run?
No. Solar generators have no fuel cost; the battery only supplies the watts your loads draw. A larger unit simply has the headroom available. The 3300's free 200W panel recharges it from sunlight at no ongoing cost.
Where do the default watts in the calculator come from?
They are typical residential estimates for common appliances, provided so the tool works before you edit anything. They are not product specs: check your own appliance labels or manuals for accurate numbers, and edit the fields to match.
Complete your plan
Food is the first pillar. Round out your preparedness with the related gear covered on this page.
Grid Doctor 300
The lighter pick if you only need phone, tablet and small-device charging.
Expansion batteries (2,048Wh each)
Add up to 7 to reach 16,384Wh of storage. Sold separately.
Extra 200W solar panels
Run up to five panels for 1,000W of solar charging. [OWNER: confirm panel price]
Related guides
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