Short answer: an 80W rooftop solar kit returns about 20 amp-hours a day flat-mounted (25Ah tilted or in strong summer sun). That covers a small trailer or truck camper's lights, vent fan, water pump and device charging — roughly 25Ah a day — with the battery drifting down a few percent a day and recovering fully on the drive home. It does not keep up with a 12V compressor fridge or a furnace running every night. If either of those is on your list, start at 200W.
This is the budget we walk through with customers choosing between the 80W Eco kit and the 200W Overlander kit. Harvest is modeled at 4.5 peak sun hours (a typical spring-to-fall day across most of the US) and 70% of panel nameplate for a flat roof mount; loads are the figures published by the appliance makers and the values RV technicians commonly measure. Treat every number as ±20% and the conclusions hold.
What a weekend actually draws
| Load | Per day |
|---|---|
| LED ceiling and reading lights, 4 fixtures × 4 h | 6 Ah |
| Roof vent fan on low, 8 h overnight | 12 Ah |
| Water pump, showers and dishes | 3 Ah |
| Two phones, a tablet and a headlamp | 6 Ah |
| Propane furnace blower, 3 h on a 35°F night | 22 Ah |
| 12V compressor cooler/fridge, 24 h | 45 Ah |
The first four rows — the "basics" — add up to about 27Ah on a long summer day and nearer 20Ah when you are outside most of the time. The furnace and the fridge are the two loads that change the category of solar you need.
Day-by-day: 80W kit, basics only
Three-day weekend, basics at 25Ah a day, 80W harvest of 20Ah a day starting the morning after the first night. The first day's draw comes out of a full battery before any sun goes back in.
| Battery | Usable capacity | End of day 1 | End of day 2 | End of day 3 | Verdict |
|---|---|---|---|---|---|
| 100Ah AGM (50% floor) | 50Ah | 75Ah (75%) | 70Ah (70%) | 64Ah (64%) | Fine — recovers on the drive |
| 100Ah lithium (Go Power! Advanced) | 90Ah | 75Ah (75%) | 70Ah (70%) | 64Ah (64%) | Comfortable |
| 2 × 6V 225Ah AGM (225Ah, 50% floor) | 112Ah | 200Ah (89%) | 195Ah (87%) | 189Ah (84%) | Comfortable |
On a single 100Ah AGM you finish the weekend around 65% — above the 50% floor that protects lead-acid life — and the kit's 10A controller brings it back to full in a couple of days parked at home. Tilt the panel toward the sun on a spring trip and harvest climbs to about 25Ah, which turns the basics into a break-even. On lithium, which lets you use 90% of the nameplate, the same kit stretches a 100Ah battery through a five-day trip.
Day-by-day: add the furnace
Add 22Ah of furnace blower on each 35°F night — fall in the mountains — and daily draw becomes 47Ah against 20Ah of solar.
| Battery | End of day 1 | End of day 2 | End of day 3 | Verdict |
|---|---|---|---|---|
| 100Ah AGM (50% floor) | 53Ah (53%) | 26Ah (26%) | 0Ah (0%) | 1 night within the healthy floor, then drive or generator |
| 100Ah lithium | 53Ah (53%) | 26Ah (26%) | 0Ah (0%) | 2 nights within the healthy floor, then drive or generator |
| 2 × 6V 225Ah AGM | 178Ah (79%) | 151Ah (67%) | 123Ah (55%) | Covered |
A single 100Ah AGM is at the 50% floor after the first night and well below it after the second; a 100Ah lithium gets you two nights. This is the trip where owners conclude that "solar doesn't work" — it works, there just isn't enough of it for a furnace. Two 6V golf-cart batteries buy a day; a 200W kit (49Ah a day) turns the furnace weekend into a surplus on lithium and a wash on AGM.
The fridge test
A 12V compressor cooler or fridge averages 45–60Ah a day in summer. Against 20Ah of solar you lose 25–40Ah every day regardless of battery size; a 100Ah lithium is empty on day three. This is the clearest line in RV solar: a fridge means 200W minimum. The 200W Overlander kit covers a fridge on an average day; the 400W Overlander kit covers fridge, basics and furnace with margin.
Where the 80W kit is the right answer
- Teardrops, pop-ups, small travel trailers and truck campers with one battery and no compressor fridge.
- Weekend and long-weekend trips with propane cooking and a three-way (absorption) fridge, which draws under 1Ah a day on propane.
- Rigs that live in storage between trips — 80W keeps the battery full and healthy year-round, which is the single biggest factor in how long a lead-acid battery lasts.
- Budget: the kit includes the panel, the GP-SB-PWM-10 controller with a lithium profile, MC4 wiring and mounting feet, so there is nothing else to buy, and the controller accepts a second panel later.
Three things that change the math
Tilt. A panel aimed at the sun in spring or fall produces 20–30% more than one lying flat. The adjustable tilt mount makes this a two-minute job at camp.
Shade. A shadow across one row of cells from the air conditioner shroud or a tree branch can cut output by half. Mount clear of the A/C and park accordingly.
Battery chemistry. Lead-acid gives you half its rating before you damage it; lithium gives you 90%. The same 80W kit on a 100Ah Advanced Lithium behaves like 80W on a 180Ah AGM bank, and lithium accepts every amp the panel makes instead of tapering as it fills.
Sizing rule of thumb
Match panel watts to battery amp-hours: 100W per 100Ah recovers an overnight draw by mid-afternoon. Then check the two category loads — fridge and furnace — and step up to 200W if either is on the list. Everything on this page assumes the equipment RV manufacturers have installed from Go Power! since 1996: the same panels, controllers and connectors, so an 80W kit today becomes a 200W or 400W system later by plugging in panels with MC4 branch connectors.
FAQ
Can an 80W solar kit run a CPAP?
Yes, with care. A CPAP without a humidifier draws about 3A for 8 hours, 25Ah a night; add the basics and you are at 50Ah a day against 20Ah of solar. On lithium that is a two-night trip; on AGM one night. A 200W kit makes CPAP camping routine.
How long does an 80W panel take to recharge a 100Ah battery from 50%?
About 2.5 days flat-mounted (50Ah ÷ 20Ah a day), or two days tilted. On a 12V lithium it is the same arithmetic without the tapering lead-acid shows above 80%.
Will it charge a lithium battery?
Yes. The included GP-SB-PWM-10 controller has a selectable LiFePO4 profile as well as AGM, gel and flooded settings.
Can I add a second panel later?
Yes. The 10A controller handles up to 200W of 12V panels; add an 80W module with an MC4 branch connector, or move to a 30A controller and 200W panels.